WO2005110464A2 - Irx5 inhibition as treatment for hyperproliferative disorders - Google Patents

Abstract

This disclosure relates to inhibition of the Iroquois family of nucleic acids and/or proteins, such as IRX1, IRX2, IRX3, IRX4, IRX5, or IRX6 in the treatment of hyperproliferative disorders. In particular, pharmaceuticals and other compositions including an IRX5 inhibitor (such as an IRX5-specific siRNA or shRNA and methods of using IRX5 inhibitors (alone or in combination therapy)to treat hyperproliferative disorders (such as neoplasia) are described.

Description

IRX5 INHIBITION AS TREA TMENT FOR HYPERPROLIFERATIVE DISORDERS

REFERENCE TO RELATED APPLICATIONS This application claims the benefit of U.S. Provisional Application No. 60/571,043, filed May 14, 2004, which application is incorporated herein in its entirety.

STATEMENT OF GOVERNMENT SUPPORT This invention was made with United States government support pursuant to grant no. 5-M01-RR00334-37 from the National Institutes of Health, National Center for Research Resources; and grant no. PC040477 from the U.S. Department of Defense; the United States government has certain rights in the invention.

FIELD This disclosure relates to methods of treating hyperproliferative disorder (such as, neoplasm) by affecting the expression of an Iroquois homeobox gene family member, in particular IRX5, and/or an activity of a corresponding protein product, such as IRX5. Also disclosed are methods of screening for inhibitors of the Iroquois family of nucleic acids and/or proteins, in particular IRX5.

BACKGROUND Homeodomain proteins constitute a large family of transcription factors characterized by a 60-amino acid domain (the homeodomain) that binds to certain regions of DNA. The homeodomain was first discovered in those proteins whose absence or misregulation caused homeotic transformations of Drosophila segments. Homeodomain proteins are developmental regulators that are essential for growth and differentiation and their anomalous expression has been detected in many cancers (De Vita et al, Eur. J. Cancer, 29A:887, 1993; Friedmann et al, Cancer Res., 54:5981, 1994; Stuart et al, Adv. Genet, 33:255, 1995; Abate-Shen, Nat. Rev. Cancer, 2:777, 2002). One family of homeodomain proteins is encoded by the Iroquois homeobox gene family, which includes IRX 1-6 in humans. Members of this gene family play multiple roles in patterning and regionalization of embryonic tissues during development in both invertebrates and vertebrates (Dambly-Chaudiere and Leyns, Int. J. Dev. Biol, 36:85, 1992; Leyns et al., Meek Dev., 59:63, 1996; ^■ Belle&oid et al., EMBOJ., 1(17):191, 1998; Gomez-Skanneta et al., EMBO J., 17:181, 1998; Goriely et al, Meek Dev., 87:203, 1999; Bosse et al, Dev. Dyn., 218:160, 2000; Peters et al, Genome Res., 10:1453, 2000; Beer et al, Proc. Am. Assoc. Cancer Res., 43:388, 2002). Iroquois protein products bind DNA through their homeodomain motif and appear to act as both transcriptional activators and repressors (Wang et al., J. Biol. Chem., 276:28835, 2001; Kudoh and Dawid, Proc. Natl. Acad. Sci. USA, 98:7852, 2001). For example, during vertebrate heart development, an inhibitory complex composed of the IRX4 protein, vitamin D receptor (VDR) and retinoic X receptor alpha binds the vitamin D response element in the slow myosin heavy chain 3 gene (Wang et al, J. Biol. Chem., 276:28835, 2001). However, little is known about the function of members of the human Iroquois homeobox gene family in higher vertebrates, particularly in humans. Vitamin D is a generic term for a family of secosteroids that have affinity for the Vitamin D receptor, and are involved in the physiologic regulation of calcium and phosphate metabolism. Vitamin D₃ is synthesized in human skin from 7-dehydrocholesterol and ultraviolet light. Vitamin

D₃, or its analog Vitamin D₂, can be ingested from the diet, for example in fortified milk products.

Vitamin D₂ and D₃ undergo hydroxylation first in the liver to 25-hydroxyvitamin D, then in the kidney to lα,25-dihydroxycholecalciferol (also known as 1,25-dihydroxyvitamin D or calcitriol), which is the principal biologically active form of Vitamin D. In 1981, Abe et al. reported that mouse myeloid leukemia cells possessed VDR and that exposure to Vitamin D led to terminal differentiation of the cells (Proc. Natl. Acad. Sci. USA,

78:4990-4994, 1981). Since then VDR has been described in carcinomas of the prostate, breast, colon, lung, pancreas, endometrium, bladder, cervix, ovaries, squamous cell carcinoma, renal cell carcinoma, myeloid and lymphocytic leukemia, medullary thyroid carcinoma, melanoma, multiple myeloma, retinoblastoma, sarcomas of the soft tissues and bone, and other malignant diseases. In vitro assays using 1,25-dihydroxyvitamin D or its analogues demonstrated antiproliferative effects in cell lines derived from many malignancies including, but not limited to, adenocarcinomas of the prostate (see, for example, Mol. Cell. Endocrinol., 126:83-90, 1997; Proc.

Amer. Assoc. Cancer Res., 38:456, 1997; J. Steroid Biochem. Mol Biol., 58:277-288, 1996; Endocrinology, 137:551-561, 1996; Endocrinology, 136:20-26, 1995; Cancer Res., 54:805-810,

1994; Endocrinology, 132:1952-1960, 1993; Anticancer Res., 14:1077-1081, 1994), breast (Proc.

Amer. Assoc. Cancer Res., 38-456, 1997; Biochem. Pharmacol, 44:693-702, 1 92); colon (Biochem.

Biophys. Res. Comm., 179:57-62, 1991; Arch. Pharmacol, 347:105-110, 1993); pancreas (Br. J.

Cancer, 73:1341-1346, 1996); endometrium (J Obstet. Gynaecol. Res., 22:529-539, 1996); lung (Anticancer Res., 16:2953-2659, 1996); myeloid leukemia (Proc. Natl. Acad. Sci. USA, 78:4990-

4994, 1981); melanoma (Endocrinology, 108:1083-1086, 1981); and sarcomas of the soft tissues

(Ann. Surg. Oncol, 3:144-149, 1996) and bone (J. Japanese Orthopaedic Assoc, 69:181-190, 1995). Because of its antiproliferative effects, Vitamin D therapy (in the form of high dose calcitriol) has been found to be a successful in vivo treatment for certain human cancers (see, for example, U.S. Pat. No. 6,521,608). However, it is desirable to identify additional agents (such as downstream targets of Vitamin D that can mediate its antiproliferative effects) for the treatment of hyperproliferative disorders, such as neoplasia.

SUMMARY This disclosure concerns the discovery that inhibition of the Iroquois family of nucleic acids and/or proteins, such as IRXl (GenBank Accession No. XM_380171), IRX2 (GenBank Accession No. NM_033267), IRX3 (GenBank Accession No. NM_024336), IRX4 (GenBank Accession No. NM_016358), IRX5 (SEQ ID NO: 1 or 3), or IRX6 (GenBank Accession No. NM_024335), can be used to treat hyperproliferative disorders in vertebrates, such as humans. In the course of determining the molecular effects of Vitamin D on prostate cancer, the inventors have surprisingly discovered that human Iroquois homeobox protein 5 (IRX5) is downregulated by Vitamin D treatment. Moreover, inhibiting expression of IRX5 reduces tumor cell growth and induces apoptosis. This important discovery shows that inhibition of IRX5 expression and/or activity at the nucleic acid or protein level can be a useful cancer treatment. In one particular aspect, the applicability of IRX5 inhibitory agents to human treatment is clear because the discovery was made in humans with cancer. Furthermore, because IRX5 expression is believed to be limited in the non-embryonic subject to predominantly neoplastic cells, inhibition of IRX5 expression and/or activity is useful to treat a broad range of malignancies. In addition, such IRX5-based treatments will be selective for tumor cells, which is a feature of treatments that are safe and well tolerated by recipients. IRX5 inhibitory agents can function as standalone therapies or can be used in combination with other drug treatments, such as vitamin D therapy or other cancer drugs and/or treatments. The foregoing and other features and advantages will become more apparent from the following detailed description of several embodiments, which proceeds with reference to the accompanying figures.

BRIEF DESCRIPTION OF THE FIGURES FIG. 1 shows a cluster analysis of the expression of 156 genes in calcitriol-treated and control (i.e., placebo-treated) prostatectomy tissues. FIG. 2 is a bar graph showing IRX5 mRNA expression (as determined by real time reverse transcriptase PCR (RT-PCR)) in calcitriol-treated human subjects versus placebo-treated subjects. The results represent an average of three experiments. FIG. 3 is a bar graph showing a time course of IRX5 mRNA expression (as determined by real time RT-PCR) in LNCaP cells treated with 10 nM Vitamin D (l,25(OH)₂D₃). The results represent an average of three experiments. FIG. 4 is a bar graph showing LNCaP cell proliferation 96 hours after transfection with two different IRX5 small inhibitory RNAs ("IRX5 #1" and "IRX5 #2") or a control oligonucleotide ("CY3 Luc GL2"). FIG. 5 is a time course of LNCaP cell numbers after transfection with IRX5 siRNA. FIG. 6 shows a bar graph of LNCaP cell numbers at 96 hours after transfection with IRX5 siRNA#2, IRX5 siRNA#3, and GL2 control siRNA. FIG. 7 shows a dose response curve for LNCaP cells treated with Vitamin D (l,25(OH)₂D₃). FIG. 8 shows the number of apoptotic LNCaP cells over time following transfection of the cells with 200 nm IRX5 siRNA or GL2 control siRNA. FIG. 9 is a composite of two digital fluorescence micrographs showing Hoechst stain 96 hours after transfection of LNCaP cells with control siRNA (left panel) or IRX5 siRNA#2 (right panel). FIG. 10 shows a Western blot of PARP cleavage product in lysates of LNCaP cells transfected with IRX5 siRNA#2, IRX5 siRNA#3, and GL2 control siRNA. FIG. 11 shows a Western blot of PARP cleavage product in lysates of LNCaP cells transfected with IRX5 siRNA#3 ("SB"), and GL2 control siRNA at the indicated time points (in hours). FIG. 12 shows a Western blot of PARP cleavage product in lysates of LNCaP cells transfected with IRX5 siRNA#3 ("Si3") or GL2 control siRNA ("GL2"), or treated with Vitamin D (l,25(OH)₂D₃) ("VD3") for the indicated times (in hours). FIG. 13 shows the percentage of LNCaP cells undergoing apoptosis at the indicated times following treatment of the cells with 10 nM or 100 nM Vitamin D ( 1 ,25(OH)₂D₃), or with a vehicle-only control. FIG. 14 is a bar graph of the number of siGL2-transfected ("G") or IRX5 siRNA#2-transfected ("2") LNCaP cells observed after 96 hours in the absence ("V-") or presence ("V+") of l,25(OH)₂D₃. FIG. 15 is a bar graph showing LNCaP cell proliferation 96 hours after transfection with pENTR/Hl/TO shRNA vectors expressing shIRX5 or'shGL2 (negative control). FIG. 16 is a bar graph of the number of pcDNA3-IRX5- (+15) or pcDNA3 (-I5)-transfected LNCaP cells (y-axis) in the presence (+VD) or absence (-VD) of l,25(OH)₂D₃. FIG. 17 is a digital image of a Western blot of p21 expression in pcDNA3-IRX5- (15) or pcDNA3 (PC; negative control)-transfected LNCap cell extracts. Protein extracts were prepared at the indicated times, β-tubulin (β-tub) expression was used as a loading control. FIG. 18 is a bar graph showing the relative expression of a luciferase reporter gene under the control of 1500 base pairs of the IRX5 gene regulatory region in the absence (1500 only) and presence (VD/1500) of (l,25(OH)₂D₃. Results from three separate trials are shown as a quotient of luciferase/β-gal expression multiplied by ten to standardize.

SEQUENCE LISTING The nucleic and amino acid sequences listed in the accompanying sequence listing are shown using standard letter abbreviations for nucleotide bases, and three letter code for amino acids, as defined in 37 C.F.R. 1.822. Only one strand of each nucleic acid sequence is shown, but the complementary strand is understood as included by any reference to the displayed strand. It is understood that the IRX5 cDNA sequences shown in SEQ ID NOs: 1 and 3 also represent corresponding IRX5 mRNAs when "T" in the DNA sequence is substituted with "U" in the mRNA sequence. In the accompanying sequence listing: SEQ ID NO: 1 shows a human IRX5 nucleic acid sequence (from GenBank Accession

No. NM_005853.3). SEQ ID NO: 2 shows a human IRX5 amino acid sequence encoded by the nucleic acid sequence in SEQ ID NO: 1. SEQ ID NO: 3 shows a human IRX5 nucleic acid sequence (from GenBank Accession No. NM_005853.4). SEQ H) NO: 4 shows a human IRX5 amino acid sequence encoded by the nucleic acid sequence in SEQ ID NO: 65. SEQ ID NO: 5 shows a RNA target sequence for IRX5 siRNA#l . SEQ ID NO: 6 shows the sense strand of IRX5 siRNA#l. SEQ ID NO: 7 shows the antisense strand of IRX5 siRNA#l. SEQ ID NO: 8 shows a RNA target sequence for IRX5 siRNA#2. SEQ ID NO: 9 shows the sense strand of IRX5 siRNA#2. SEQ ID NO: 10 shows the antisense strand of IRX5 siRNA#2. SEQ ID NO: 11 shows a RNA target sequence for IRX5 siRNA#3. SEQ ID NO: 12 shows the sense strand of IRX5 siRNA#3. SEQ ID NO: 13 shows the antisense strand of IRX5 siRNA#3. SEQ TD NO: 14 shows a RNA target sequence for GL2 control siRNA. SEQ ID NO: 15 shows the sense strand of the GL2 control siRNA. SEQ ID NO: 16 shows the antisense strand of the GL2 control siRNA. SEQ ID NOs: 17-108 show the sense strands of several other IRX5 siRNA embodiments. SEQ ID NOs: 109-110 show paired oligonucleotides that when hybridized together form a dsDNA sequence encoding IRX5 shRNA2. SEQ ID NOs: 111-112 show paired oligonucleotides that when hybridized together form a dsDNA sequence encoding IRX5 shRNA3. SEQ ID NOs: 113-114 show paired oligonucleotides that when hybridized together form a dsDNA sequence encoding IRX5 shRNA4. SEQ ID NOs: 115-116 show paired oligonucleotides that when hybridized together form a dsDNA sequence encoding the control shRNA, shRNA-GL2. SEQ ID NOs: 117-119 show the RNA sequences of shRNA2, shRNA3, and shRNA4, respectively. SEQ ID NOs: 120-138 show exemplary DNA sequences encoding IRX5-specific shRNAs. SEQ ID NOs: 139-150 show representative PCR primers useful for amplifying an IRX5 gene regulatory region.

An IRX5 siRNA has a corresponding sense strand and an antisense strand that together form a double-stranded siRNA specific for the target sequence. In particular embodiments, a sense strand of an IRX5 siRNA has two 2'-deoxythymidine (dT) residues added to its 3' end. Thus, for example, the sense strand of an IRX5 siRNA (e.g., IRX5 siRNA#2) that targets the sequence

5'-GAGAGAGACAGAGAGAGAA-3' (SEQ ID NO: 8 and also residues 1526-1544 of SEQ ID NO: 1) would be 5'-GAGAGAGACAGAGAGAGAA-dT-dT-3' (SEQ ID NO: 9). In these same embodiments, the sequence of the antisense strand of the IRX5 siRNA is the complement of the sense strand with the addition of two 2'-deoxythymidine (dT) residues to its 3' end. Thus, the antisense strand of the above exemplary IRX5 siRNA would have the sequence 5'-UUCUCUCUCUGUCUCUCUC-dT-dT-3' (SEQ ID NO: 10). In this manner, embodiments of sense and antisense strands of IRX5 siRNAs specific for any IRX5 target sequence may be readily determined by one of ordinary skill in the art. The following table shows further examples of the sense and antisense strands of IRX5 siRNAs, which are specific for the indicated IRX5 target sequences.

DETAILED DESCRIPTION /. Introduction Disclosed herein are methods of treating a hyperproliferative disorder, such as neoplasm, by administering to a subject a therapeutically effective amount of an IRX5 inhibitor, which thereby treats the hyperproliferative disorder. In some examples, an IRX5 inhibitor is other than a Vitamin D drug (such as, other than calcitriol). In other examples, an IRX5 inhibitor is a small inhibitory RNA (siRNA), an anti-sense nucleic acid, a ribozyme, an aptamer, a mirror-image aptamer, an IRX5 dominant negative peptide, an IRX5 inhibitory antibody, or a combination thereof. In more particular examples, the IRX5 inhibitor is a siRNA, such as a siRNA that targets a nucleic acid sequence (and/or has the sense strand) including a sequence as set forth in SEQ ID NO: 5, 6, 8, 9, 11, 12, or 17-108, or a siRNA that targets a nucleic acid sequence (and/or has the sense strand) including the sequence as set forth in SEQ ID NO: 5, 6, 8, 9, 11, or 12. In some embodiments of the disclosed methods, administration of a siRNA results in apoptosis of at least 5% of the neoplastic cells. Some implementations of the disclosed methods treat neoplasms, including cancer of the prostate, breast, colon, lung, head and neck, pancreas, endometrium, bladder, cervix, ovaries, squamous cell carcinoma, renal cell carcinoma, myeloid and lymphocytic leukemia, lymphoma, medullary thyroid carcinoma, melanoma, multiple myeloma, retinoblastoma, and sarcomas of the soft tissues and bone. In specific methods, the neoplasm is prostate cancer. Also contemplated herein are combination therapies including administration of an IRX5 inhibitor with a Vitamin D drug (such as calcitriol) or other chemotherapeutic agents (such as taxanes, which include, for example, paclitaxel and docetaxel; or antimitotic agents, which include, for example, paclitaxel, docetaxel, epothilone A, epofhilone B, discodermolide, laulimalide or a combination thereof), or other cancer therapies (such as, radiation therapy or hormone therapy). In embodiments involving administration of calcitriol, the calcitriol is administered in a therapeutically effective pulse dose no more than once every three days. Alternatively, the calcitriol is administered orally in a dose of at least 0.12 meg (μg)/kg per day no more than once per week. In yet another alternative, the calcitriol is administered orally in a dose of at least 0.48 mcg/kg or about 1 mcg/kg per day no more than once per week. Further disclosed are methods for identifying potential therapeutic agents (such as, anti-proliferative therapeutic agents) by determining IRX5 inhibitory activity of an agent, wherein inhibition of IRX5 activity by the agent identifies the agent as a potential therapeutic agent (such as, a potential anti-proliferative therapeutic agent). In some examples, the potential therapeutic agent is useful in the treatment of a neoplasm, such as, cancer of the prostate, breast, colon, lung, head and neck, pancreas, endometrium, bladder, cervix, ovaries, squamous cell carcinoma, renal cell carcinoma, myeloid and lymphocytic leukemia, lymphoma, medullary thyroid carcinoma, melanoma, multiple myeloma, retinoblastoma, and sarcomas of the soft tissues and bone. In some instances, the agent includes a small inhibitory RNA (siRNA), an anti-sense nucleic acid, a ribozyme, an aptamer, a mirror-image aptamer, an IRX5 peptide, an IRX5 inhibitory antibody, or a combination thereof. In more specific embodiments, the agent is a siRNA. Another method of identifying potential therapeutic agents (such as, anti-proliferative therapeutic agents) disclosed herein involves providing a test cell that expresses an IRX5 nucleic acid or an IRX5 protein, contacting the test cell with an agent, and determining whether the agent inhibits at least one of: (i) expression of the IRX5 nucleic acid, or (ii) activity of the IRX5 protein. An agent that inhibits IRX5 nucleic acid expression and or IRX5 protein activity identifies the agent as a potential therapeutic agent. In some exemplary methods, the potential therapeutic agent is useful in the treatment of neoplasm, such as prostate cancer. Also disclosed herein are IRX5 inhibitors, such as siRNA, an anti-sense nucleic acid, a ribozyme, an aptamer, a mirror-image aptamer, an IRX5 dominant negative peptide, an IRX5 inhibitory antibody, or a combination thereof. In particular examples, an IRX5 inhibitor is a siRNA, such as a siRNA that targets a nucleic acid sequence (and/or has the sense strand) that includes the sequence as set forth in SEQ ID NO: 5, 6, 8, 9, 11, 12, or 17-108. For example, a siRNA that targets a nucleic acid sequence (and/or has the sense strand) including the sequence as set forth in SEQ ID NO: 5, 6, 8, 9, 11, or 12. Further disclosed herein are pharmaceutical compositions including an IRX5 inhibitor and a pharmaceutically acceptable carrier.

II. Abbreviations and Terms l,25(OH)₂D₃ l,25-Dihydroxyvitamin D3 dsRNA double stranded RNA IRX5 Iroquois homeobox protein 5 meg microgram ORF open reading frame Real-time RT-PCR real time reverse transcriptase polymerase chain reaction RNAi RNA interference shRNA small (or short, or synthetic) hairpin RNA siRNA small interfering RNA VDR vitamin D receptor

Unless otherwise noted, technical terms are used according to conventional usage. Definitions of common terms in molecular biology may be found in Benjamin Lewin, Genes V, published by Oxford University Press, 1994 (ISBN 0-19-854287-9); Kendrew et al. (eds.), The Encyclopedia of Molecular Biology, published by Blackwell Science Ltd., 1994 (ISBN 0-632-02182- 9); and Robert A. Meyers (ed.), Molecular Biology and Biotechnology: a Comprehensive Desk Reference, published by VCH Publishers, Inc., 1995 (ISBN 1-56081-569-8). In order to facilitate review of the various embodiments of the invention, the following explanations of specific terms are provided: Agent: Any substance (such as, an atom, molecule, molecular complex, chemical, peptide, protein, protein complex, nucleic acid, or drug) or any combination of substances that is useful for achieving an end or result; for example, a substance or combination of substances useful for inhibiting gene expression or inhibiting protein activity, or useful for modifying or interfering with protein-protein interactions. Similarly, a "component" is any substance (such as, an atom, molecule, molecular complex, chemical, peptide, protein, protein complex, nucleic acid, or drug) that is useful for achieving an end or result. Analog, derivative or mimetic: An analog is a molecule that differs in chemical structure from a parent compound, for example a homolog (differing by an increment in the chemical structure, such as a difference in the length of an alkyl chain), a molecular fragment, a structure that differs by one or more functional groups, a change in ionization. Structural analogs are often found using quantitative structure activity relationships (QSAR), with techniques such as those disclosed in Remington (The Science and Practice of Pharmacology, 19th Edition (1995), chapter 28). A derivative is a biologically active molecule derived from the base structure. A mimetic is a molecule that mimics the activity of another molecule, such as a biologically active molecule. Biologically active molecules can include chemical structures that mimic the biological activities of a compound. Antibody: An intact immunoglobulin or an antigen-binding portion thereof. Antigen-binding portions may be produced by recombinant DNA techniques or by enzymatic or chemical cleavage of intact immunoglobulins. Antigen-binding portions include, inter alia, Fab, Fab', F(ab')2_> Fv, dAb (Fd), and complementarity determining region (CDR) fragments, single-chain antibodies (scFv), chimeric antibodies, diabodies and polypeptides (including fusion proteins) that contain at least a portion of an immunoglobulin that is sufficient to confer specific antigen binding to the polypeptide. A Fab fragment is a monovalent fragment consisting of the VL, VH, CL and CHI domains; an F(ab')2 fragment is a bivalent fragment comprising two Fab fragments linked by a disulfide bridge at the hinge region; an Fd fragment consists of the VH and CHI domains; an Fv fragment consists of the VL and VH domains of a single arm of an antibody; and a dAb fragment consists of a VH domain (see, e.g., Ward et al, Nature, 341:544-546, 1989). The terms "bind specifically" and "specific binding" refer to the ability of a specific binding agent (such as, an antibody) to bind to a target molecular species in preference to binding to other molecular species with which the specific binding agent and target molecular species are admixed. A specific binding agent is said specifically to "recognize" a target molecular species when it can bind specifically to that target. A "single-chain antibody" (scFv) is a genetically engineered molecule containing the VH and VL domains of one or more antibody(ies) linked by a suitable polypeptide linker as a genetically fused single chain molecule (see, e.g., Bird et al, Science, 242:423-426, 1988; Huston et al, Proc.

Natl. Acad. Sci., 85:5879-5883, 1988). Diabodies are bivalent, bispecific antibodies in which VH and VL domains are expressed on a single polypeptide chain, but using a linker that is too short to allow for pairing between the two domains on the same chain, thereby forcing the domains to pair with complementary domains of another chain and creating two antigen binding sites (see, e.g., Holliger et al, Proc. Natl. Acad. Sci., 90:6444-6448, 1993; Poljak et al, Structure, 2: 1121-1123, 1994). One or more CDRs may be incorporated into a molecule either covalently or noncovalently to make the resultant molecule an immunoadhesin. An immunoadhesin may incorporate the CDR(s) as part of a larger polypeptide chain, may covalently link the CDR(s) to another polypeptide chain, or may incorporate the CDR(s) noncovalently. The CDRs permit the immunoadhesin to specifically bind to a particular antigen of interest. A chimeric antibody is an antibody that contains one or more regions from one antibody and one or more regions from one or more other antibodies. An antibody may have one or more binding sites. If there is more than one binding site, the binding sites may be identical to one another or may be different. For instance, a naturally-occurring immunoglobulin has two identical binding sites, a single-chain antibody or Fab fragment has one binding site, while a "bispecific" or "bifunctional" antibody has two different binding sites. A "neutralizing antibody" or "an inhibitory antibody" is an antibody that inhibits at least one activity of a polypeptide, such as by blocking the binding of the polypeptide to a ligand to which it normally binds, or by disrupting or otherwise interfering with a protein-protein interaction of the polypeptide with a second polypeptide. An "activating antibody" is an antibody that increases an activity of a polypeptide. Aptamer: A single-stranded nucleic acid molecule (such as, DNA or RNA) that assumes a specific, sequence-dependent shape and binds to a target protein with high affinity and specificity. Aptamers generally comprise fewer than 100 nucleotides, fewer than 75 nucleotides, or fewer than 50 nucleotides. "Mirror-image aptamer(s)" (also called Spiegelmers™) are high-affinity L-enantiomeric nucleic acids (for example, L-ribose or L-2'-deoxyribose units) that display high resistance to enzymatic degradation compared with D-oligonucleotides (such as, aptamers). The target binding properties of mirror-image aptamers are designed by an in vz rø-selection process starting from a random pool of oligonucleotides, as described for example, in Wlotzka et al, Proc. Natl. Acad. Sci. 99(13):8898-8902, 2002. Applying this method, high affinity mirror-image aptamers specific for a polypeptide (such as, IRX5) can be generated. Cancer or Neoplasia: A biological condition in which a neoplasm has undergone characteristic anaplasia with loss of differentiation, increased rate of growth, invasion of surrounding tissue, and which is capable of metastasis. The resultant neoplasm is also known as a malignant tumor. The term(s) includes breast carcinomas (e.g. lobular and duct carcinomas), and other solid tumors, sarcomas, and carcinomas of the lung like small cell carcinoma, large cell carcinoma, squamous carcinoma, and adenocarcinoma, mesothelioma of the lung, colorectal adenocarcinoma, stomach carcinoma, prostatic adenocarcinoma, ovarian carcinoma such as serous cystadenocarcinoma and mucinous cystadenocarcinoma, ovarian germ cell tumors, testicular carcinomas, and germ cell tumors, pancreatic adenocarcinoma, biliary adenocarcinoma, heptacellular carcinoma, bladder carcinoma including transitional cell carcinoma, adenocarcinoma, and squamous carcinoma, renal cell adenocarcinoma, endometrial carcinomas including adenocarcinomas and mixed Mullerian tumors (carcinosarcomas), carcinomas of the endocervix, ectocervix, and vagina such as adenocarcinoma and squamous carcinoma, tumors of the skin like squamous cell carcinoma, basal cell carcinoma, melanoma, and skin appendage tumors, esophageal carcinoma, carcinomas of the nasopharynx and oropharynx including squamous carcinoma and adenocarcinomas, salivary gland carcinomas, brain and central nervous system tumors including tumors of glial, neuronal, and meningeal origin, tumors of peripheral nerve, soft tissue sarcomas and sarcomas of bone and cartilage. Also included are non-solid hematopoietic tumors, such as leukemias. Gene expression: The process by which the coded information of a nucleic acid transcriptional unit (including, for example, genomic DNA or cDNA) is converted into an operational, non-operational, or structural part of a cell, often including the synthesis of a protein. Gene expression can be influenced by external signals; for instance, exposure of a subject to an agent that inhibits gene expression, such as inhibition of IRX5 gene expression. Expression of a gene also may be regulated anywhere in the pathway from DNA to RNA to protein. Regulation of gene expression occurs, for instance, through controls acting on transcription, translation, RNA transport and processing, degradation of intermediary molecules such as mRNA, or through activation, inactivation, conipartmentalization or degradation of specific protein molecules after they have been made, or by combinations thereof. Gene expression may be measured at the RNA level or the protein level and by any method known in the art, including Northern blot, RT-PCR, Western blot, or in vitro, in situ, or in vivo protein activity assay(s). The expression of a nucleic acid may be modulated compared to a control state, such as at a control time (for example, prior to administration of a substance or agent that affects regulation of the nucleic acid under observation) or in a control cell or subject, or as compared to another nucleic acid. Such modulation includes but is not necessarily limited to overexpression, underexpression, or suppression of expression. In addition, it is understood that modulation of nucleic acid expression may be associated with, and in fact may result in, a modulation in the expression of an encoded protein or even a protein that is not encoded by that nucleic acid. Hybridization: Oligonucleotides and their analogs hybridize by hydrogen bonding, which includes Watson-Crick, Hoogsteen or reversed Hoogsteen hydrogen bonding, between complementary bases. Generally, nucleic acid consists of nitrogenous bases that are either pyrimidines (cytosine (C), uracil (U), and thymine (T)) or purines (adenine (A) and guanine (G)). These nitrogenous bases form hydrogen bonds between a pyrimidine and a purine, and the bonding of the pyrimidine to the purine is referred to as "base pairing." More specifically, A will hydrogen bond to T or U, and G will bond to C. "Complementary" refers to the base pairing that occurs between to distinct nucleic acid sequences or two distinct regions of the same nucleic acid sequence. For example, an oligonucleotide can be complementary to an IRX5-encoding mRNA, or an IRX5-encodfng dsDNA. "Specifically hybridizable" and "specifically complementary" are terms that indicate a sufficient degree of complementarity such that stable and specific binding occurs between the oligonucleotide (or its analog) and the DNA or RNA target. The oligonucleotide or oligonucleotide analog need not be 100% complementary to its target sequence to be specifically hybridizable. An oligonucleotide or analog is specifically hybridizable when binding of the oligonucleotide or analog to the target DNA or RNA molecule interferes with the normal function of the target DNA or RNA, and there is a sufficient degree of complementarity to avoid non-specific binding of the oligonucleotide or analog to non-target sequences under conditions where specific binding is desired, for example under physiological conditions in the case of in vivo assays or systems. Such binding is referred to as specific hybridization. Hybridization conditions resulting in particular degrees of stringency will vary depending upon the nature of the hybridization method of choice and the composition and length of the hybridizing nucleic acid sequences. Generally, the temperature of hybridization and the ionic strength (especially the Na⁺ and/or Mg^""^" concentration) of the hybridization buffer will determine the stringency of hybridization, though wash times also influence stringency. Calculations regarding hybridization conditions required for attaining particular degrees of stringency are discussed by Sambrook et al. (ed.), Molecular Cloning: A Laboratory Manual, 2nd ed., vol. 1-3, Cold Spring Harbor Laboratory Press, Cold Spring Harbor, NY, 1989, chapters 9 and 11. For purposes of the present disclosure, "stringent conditions" encompass conditions under which hybridization will only occur if there is less than 25% mismatch between the hybridization molecule and the target sequence. "Stringent conditions" may be broken down into particular levels of stringency for more precise definition. Thus, as used herein, "moderate stringency" conditions are those under which molecules with more than 25% sequence mismatch will not hybridize; conditions of "medium stringency" are those under which molecules with more than 15% mismatch will not hybridize, and conditions of "high stringency" are those under which sequences with more than 10% mismatch will not hybridize. Conditions of "very high stringency" are those under which sequences with more than 6% mismatch will not hybridize. In particular embodiments, stringent conditions are hybridization at 65° C in 6x SSC, 5x Denhardt's solution, 0.5% SDS and 100 μg sheared salmon testes DNA, followed by 15-30 minute sequential washes at 65° C in 2x SSC, 0.5% SDS, followed by lx SSC, 0.5% SDS and finally 0.2x SSC, 0.5% SDS. Hyperproliferative disorder: A disorder characterized by abnormal proliferation of cells, and generically includes include neoplasias (e.g., cancers), fibroproliferative disorders (such as involving connective tissues, as well as other disorders characterized by fibrosis, including for example, rheumatoid arthritis, insulin dependent diabetes mellitus, glomerulonephritis, cirrhosis, and scleroderma), smooth muscle proliferative disorders (such as atherosclerosis and restinosis), chronic inflammation, and epithelial cell proliferative disorders (for example, psoriasis; keratosis; acne; comedogenic lesions; verracous lesions such as verruca plana, plantar warts, verruca acuminata, and other verruciform lesions marked by proliferation of epithelial cells; folliculitis and pseudofolliculitis; keratoacanthoma; callosities; Darier's disease; ichfhyosis; lichen planus; molluscous contagiosum; melasma; Fordyce disease; and keloids or hypertrophic scars). Inhibiting protein activity: To decrease, limit, or block an action, function or expression of a protein, such as IRX5. The phrase "inhibiting protein activity" is not intended to be an absolute term. Instead, the phrase is intended to convey a wide-range of inhibitory effects that various agents may have on the normal (for example, uninhibited or control) protein activity. Thus, protein activity may be inhibited when the level or activity of any direct or indirect indicator of the protein's activity is changed (for example, increased or decreased) by at least 10%, at least 20%, at least 30%, at least 50%), at least 80%, at least 100%) or at least 250% as compared to control measurements of the same indicator. Inhibition of protein activity may, but need not, result in an increase in the level or activity of an indicator of the protein's activity. By way of example, this can happen when the protein of interest is acting as an inhibitor or suppressor of a downstream indicator. Inhibition of protein activity may also be effected, for example, by inhibiting expression of the gene encoding the protein or by decreasing the half-life of the mRNA encoding the protein. "Interfering with or inhibiting gene expression" refers to the ability of an agent to measurably reduce the expression of a target gene. Expression of a target gene may be measured by any method known to those of skill in the art, including for example measuring mRNA or protein levels. It is understood that interfering with or inhibiting gene expression is relative, and does not require absolute suppression of the gene. Thus, in certain embodiments, interfering with or inhibiting gene expression of a target gene requires that, following application of an agent, the gene is expressed at least 5% less than prior to application, at least 10% less, at least 15% less, at least 20% less, at least 25% less, or even more reduced. Thus, in some particular embodiments, application of an agent - reduces expression of the target gene by about 30%, about 40%, about 50%, about 60%, or more. In specific examples, where the agent is particularly effective, expression is reduced by 70%, 80%, 85%, 90%, 95%, or even more. Gene expression is "substantially eliminated" when expression of the gene is reduced by 90%, 95%, 98%, 99% or even 100%. Inhibition of cell growth: The phrase "inhibition of cell growth" (and analogous phrases, such as inhibition of cellular proliferation) does not mean absolute prohibition of cell growth and does not require cell death. Instead, the phrase is intended to be relative and convey the wide-range of inhibitory effects that an agent (e.g., an anti-proliferative agent or an IRX5 inhibitory agent) may have on the normal or typical rate of cell growth. The phrase "inhibition of cell growth" is relative to the normal (i.e., uninhibited or control) rate of growth of the particular cell or population of cells of interest. Thus, inhibition of cell growth can mean that the normal growth rate of a cell or cell population has slowed (i.e., cell number increases over time, but not as rapidly as in a control population), equals zero (i.e., there is no change in number of cells in the population over time, e.g., cell growth equals cell death), or becomes negative (i.e., the number of cells decreases over time, e.g., cell death exceeds cell growth). At the extreme, a negative rate of cell growth can (but need not) result in the death of all cells in a population. For example, an anti-proliferative agent or an IRX5 inhibitory agent may inhibit the rate of cell growth (such as, the growth of a neoplastic cell or mammalian cell), which may or may not result over time in a decrease in the absolute numbers of cells in the overall population relative to when the agent was administered. IRX5 Inhibitor: An agent that directly or indirectly inhibits IRX5 gene, mRNA or protein expression and/or activity; for example, siRNAs or shRNAs specific for IRX5 mRNA, which can decrease IRX5 mRNA levels and thereby decrease IRX5 protein expression and/or activity. The activity of an IRX5 inhibitor is referred to as "IRX5 inhibitory activity." In some examples, an IRX5 inhibitor excludes a Vitamin D drug (such as, calcitriol). Isolated: An "isolated" biological component (such as a nucleic acid molecule, protein, antibody or organelle) has been separated or purified away from other biological components in the cell of the organism in which the component naturally occurs, for instance, other chromosomal and extra-chromosomal DNA and RNA, proteins, antibodies and organelles. Nucleic acids and proteins that have been "isolated" include nucleic acids and proteins purified by standard purification methods. The term also embraces nucleic acids and proteins prepared by recombinant expression in a host cell, as well as chemically synthesized biopolymers. The term "isolated" does not require absolute isolation. Similarly, the term "substantially separated" does not require absolute separation. Neoplasm: An abnormal growth of cells or tissue, particularly a new growth of cells or tissue in which the growth is uncontrolled and progressive. "Neoplastic cells" are those cells within a neoplasm that exhibit abnormal growth. Tumors or other cancers are examples of neoplasms. A tumor that does not metastasize is referred to as "benign." A tumor that invades the surrounding tissue and/or can metastasize is referred to as "malignant." Neoplasia is the pathological process that results in the formation of a neoplasm. Neoplasia is one example of a proliferative disorder. Nucleic acid molecule: A polymeric form of nucleotides, which may include both sense and anti-sense strands of RNA, cDNA, genomic DNA, and synthetic forms and mixed polymers of the above. A nucleotide refers to a ribonucleotide, deoxynucleotide or a modified form of either type of nucleotide. A "nucleic acid molecule" as used herein is synonymous with "nucleic acid" and "polynucleotide." A nucleic acid molecule is usually at least 10 bases in length, unless otherwise specified. The term includes single- and double-stranded forms of DNA. A polynucleotide may include either or both naturally occurring and modified nucleotides linked together by naturally occurring and/or non-naturally occurring nucleotide linkages. Nucleic acid molecules may be modified chemically or biochemically or may contain non-natural or derivatized nucleotide bases, as will be readily appreciated by those of skill in the art. Such modifications include, for example, labels, methylation, substitution of one or more of the naturally occurring nucleotides with an analog, intemucleotide modifications, such as uncharged linkages (for example, methyl phosphonates, phosphotriesters, phosphoramidates, carbamates, etc.), charged linkages (for example, phosphorothioates, phosphorodithioates, etc.), pendent moieties (for example, polypeptides), intercalators (for example, acridine, psoralen, etc.), chelators, alkylators, and modified linkages (for example, alpha anomeric nucleic acids, etc.). The term "nucleic acid molecule" also includes any topological conformation, including single-stranded, double-stranded, partially duplexed, triplexed, hairpinned, circular and padlocked conformations. Also included are synthetic molecules that mimic polynucleotides in their ability to bind to a designated sequence via hydrogen bonding and other chemical interactions. Such molecules are known in the art and include, for example, those in which peptide linkages substitute for phosphate linkages in the backbone of the molecule. Unless specified otherwise, the left hand end of a polynucleotide sequence written in the sense orientation is the 5' end and the right hand end of the sequence is the 3' end. In addition, the left hand direction of a polynucleotide sequence written in the sense orientation is referred to as the 5' direction, while the right hand direction of the polynucleotide sequence is referred to as the 3' direction. Further, unless otherwise indicated, each nucleotide sequence is set forth herein as a sequence of deoxyribonucleotides. It is intended, however, that the given sequence be interpreted as would be appropriate to the polynucleotide composition: for example, if the isolated nucleic acid is composed of RNA, the given sequence intends ribonucleotides, with uridine substituted for thymidine. An "anti-sense nucleic acid" is a nucleic acid (such as, an RNA or DNA oligonucleotide) that has a sequence complementary to a second nucleic acid molecule (for example, an mRNA molecule). An anti-sense nucleic acid will specifically bind with high affinity to the second nucleic acid sequence. If the second nucleic acid sequence is an mRNA molecule, for example, the specific binding of an anti-sense nucleic acid to the mRNA molecule can prevent or reduce translation of the mRNA into the encoded protein or decrease the half life of the mRNA, and thereby inhibit the expression of the encoded protein. Oligonucleotide: A nucleic acid molecule generally comprising a length of 200 bases or fewer. The term often refers to single-stranded deoxyribonucleotides, but it can refer as well to single- or double-stranded ribonucleotides, RNA:DNA hybrids and double-stranded DNAs, among others. In some examples, oligonucleotides are about 10 to about 90 bases in length, for example, 12, 13, 14, 15, 16, 17, 18, 19 or 20 bases in length. Other oligonucleotides are about 25, about 30, about 35, about 40, about 45, about 50, about 55, about 60 bases, about 65 bases, about 70 bases, about 75 bases or about 80 bases in length. Oligonucleotides may be single-stranded, for example, for use as probes or primers, or may be double-stranded, for example, for use in the construction of a mutant gene. Oligonucleotides can be either sense or anti-sense oligonucleotides. An oligonucleotide can be derivatized or modified as discussed above in reference to nucleic acid molecules. Ribozyme: RNA molecules with enzyme-like properties, which can be designed to cleave specific RNA sequences. Ribozymes are also known as RNA enzymes or catalytic RNAs. RNA: A typically linear polymer of ribonucleic acid monomers, linked by phosphodiester bonds. Naturally occurring RNA molecules fall into three general classes, messenger (mRNA, which encodes proteins), ribosomal (rRNA, components of ribosomes), and transfer (tRNA, molecules responsible for transferring amino acid monomers to the ribosome during protein synthesis). Messenger RNA includes heteronuclear (hhRNA) and membrane-associated polysomal RNA (attached to the rough endoplasmic reticulum). Total RNA refers to a heterogeneous mixture of all types of RNA molecules. RNA interference (or, RNA silencing or RNAi): A highly conserved gene-silencing mechanism whereby specific double-stranded RNA (dsRNA) trigger the degradation of homologous mRNA (also called, target RNA) (Zamore et al, Cell, 101:25-33, 2000; Fire et al, Nature, 391:806, 1998; Hamilton et al, Science, 286:950-951, 1999; Lin et al, Nature, 402:128-129, 1999; Sharp, Genes Dev., 13:139 141, 1999; and Strauss, Science, 286:886, 1999). Double-stranded RNA is processed into small interfering RNAs (siRNA) by a ribonuclease referred to as dicer (Bass, Cell, 101:235, 2000; Zamore et al, Cell, 101:25-33, 2000; Hammond et al, Nature, 404:293, 2000). siRNAs serve as a guide for cleavage of the homologous mRNA in the RNA-induced silencing complex (RISC) (Elbashir et al, Genes Dev., 15:188, 2001). The remnants of the target RNA may then also act as siRNA; thus resulting in a cascade effect. Sequence identity: The similarity between two nucleic acid sequences, or two amino acid sequences, is expressed in terms of the similarity between the sequences, otherwise referred to as sequence identity. Sequence identity is frequently measured in terms of percentage identity (or similarity or homology); the higher the percentage, the more similar the two sequences are. Methods of alignment of sequences for comparison are well known in the art. Various programs and alignment algorithms are described in: Smith and Waterman (Adv. Appl. Math., 2:482, 1981); Needleman and Wunsch (J. Mol. Biol, 48:443, 1970); Pearson and Lipman (Proc. Natl. Acad. Sci., 85:2444, 1988); Higgins and Sharp (Gene, 73:237-244, 1988); Higgins and Sharp (CABIOS, 5:151-153, 1989); Corpet et al. (Niic. Acids Res., 16:10881-10890, 1988); Huang et al. (Comp. Appls Bioscl, 8:155-165, 1992); and Pearson et al. (Meth. Mol. Biol, 24:307-331, 1994). Altschul et al. (Nature Genet., 6:119-129, 1994) presents a detailed consideration of sequence alignment methods and homology calculations. The alignment tools ALIGN (Myers and Miller, CABIOS 4:11-17, 1989) or LFASTA (Pearson and Lipman, 1988) may be used to perform sequence comparisons (Internet Program © 1996, W. R. Pearson and the University of Virginia, "fasta20u63" version 2.0u63, release date December 1996). ALIGN compares entire sequences against one another, while LFASTA compares regions of local similarity. These alignment tools and their respective tutorials are available on the Internet at the NCSA website. Alternatively, for comparisons of amino acid sequences of greater than about 30 amino acids, the "Blast 2 sequences" function can be employed using the default BLOSUM62 matrix set to default parameters, (gap existence cost of 11, and a per residue gap cost of 1). When aligning short peptides (fewer than around 30 amino acids), the alignment should be performed using the "Blast 2 sequences" function, employing the PAM30 matrix set to default parameters (open gap 9, extension gap 1 penalties). The BLAST sequence comparison system is available, for instance, from the NCBI web site; see also Altschul et al, J. Mol. Biol, 215:403-410, 1990; Gish. and States, Nature Genet, 3:266-272, 1993; Madden et al, Meth. Enzymol, 266:131-141, 1996; Altschul et al, Nucleic Acids Res., 25:3389-3402, 1997; and Zhang and Madden, Genome Res., 7:649-656, 1997. Orfhologs (equivalent to proteins of other species) of proteins are in some instances characterized by possession of greater than 75% sequence identity counted over the full-length alignment with the amino acid sequence of specific protein using ALIGN set to default parameters. Proteins with even greater similarity to a reference sequence will show increasing percentage identities when assessed by this method, such as at least 80%, at least 85%, at least 90%, at least

92%, at least 95%, or at least 98% sequence identity. In addition, sequence identity can be compared over the full length of one or both binding domains of the disclosed fusion proteins. When significantly less than the entire sequence is being compared for sequence identity, homologous sequences will typically possess at least 80% sequence identity over short windows of 10-20, and may possess sequence identities of at least 85%>, at least 90%, at least 95%, or at least 99% depending on their similarity to the reference sequence. Sequence identity over such short windows can be determined using LFASTA; methods are described at the NCSA website. One of skill in the art will appreciate that these sequence identity ranges are provided for guidance only; it is entirely possible that strongly significant homologs could be obtained that fall outside of the ranges provided. Similar homology concepts apply for nucleic acids as are described for protein. An alternative indication that two nucleic acid molecules are closely related is that the two molecules hybridize to each other under stringent conditions. Hybridization conditions have been discussed previously. Nucleic acid sequences that do not show a high degree of identity may nevertheless encode similar amino acid sequences, due to the degeneracy of the genetic code. It is understood that changes in nucleic acid sequence can be made using this degeneracy to produce multiple nucleic acid sequences that each encode substantially the same protein. Subject: Living multicellular, vertebrate organisms, a category that includes both human and veterinary subjects for example, mammals, rodents, and birds. Therapeutic agent: Used in a generic sense, the term "therapeutic agent" includes treating agents, prophylactic agents, and replacement agents (such as, anti-proliferative therapeutic agents). The term "chemotherapeutic agents" may be used more specifically to refer to agents that kill, inhibit or slow the reproduction of rapidly multiplying cells, such as neoplastic cells. Chemotherapeutic agents are well known to those of ordinary skilled in the art and include, for example, 5-fluorouracil (5-FU), azathioprine, cyclophosphamide, antimetabolites (such as Fludarabine), antineoplastics (such as Etoposide, Doxorubicin, methotrexate, and/or Vincristine), carboplatin, Rapamycin, cis-platinum, antimitotic agents (such as paclitaxel, docetaxel, epothilone A, epothilone B, discodermolide, and/or laulimalide) and the taxanes, such as paclitaxel and/or docetaxel. Therapeutically effective amount: A quantity of a specified agent sufficient to achieve a desired effect in a subject being treated with that agent. For example, this may be the amount of an inhibitor of IRX5 gene expression or IRX5 protein activity necessary to prevent, inhibit, reduce or relieve hyperproliferative disorder, such as neoplasm, in a subject. Ideally, a therapeutically effective amount of an agent is an amount sufficient to inhibit IRX5 activity without causing a substantial cytotoxic effect in the subject. The effective amount of an agent useful for inhibiting IRX5 activity will be dependent on the subject being treated, the severity of the affliction, and the manner of administration of the therapeutic composition. An effective amount of an agent useful for inhibiting IRX5 activity may be administered in a single dose, or in several doses, for example daily, during a course of treatment. However, the frequency of administration is dependent on the preparation applied, the subject being treated, the severity and type of the affliction, and the manner of administration of the compound. Treating or treatment: With respect to disease, either term includes (1) preventing the disease, e.g., causing the clinical symptoms of the disease not to develop in an animal that may be exposed to or predisposed to the disease but does not yet experience or display symptoms of the disease, (2) inliibiting the disease, e.g., arresting the development of the disease or its clinical symptoms, or (3) relieving the disease, e.g., causing regression of the disease or its clinical symptoms. Vitamin D Drug: A drug that raises the blood or tissue level of Vitamin D, or has an affinity for the Vitamin D receptor, for example binding to that receptor with a Relative Competitive Index (RCI) of 0.05 or greater, more particularly 5 or greater, for example 5-250. The RCI is indexed to an RCI of 100 for calcitriol. The term also includes any of the family of secosteroids with antirhichitic activity, such as Vitamin D₂ (ergocalciferol) and Vitamin D₃ (cholecalciferol), their precursor molecules such as ergosterol (7-dehydro-22-dehydro-24-methyl-cholesterol) and 7 dehydrocholesterol, 25-hydroxyvitamin D_3> the 3-hydroxylated dihydrotachysterol₂, the lα- hydroxylated alfacalcidol (lα-hydroxyvitamin D₃) and calcitriol (lα, 25-dihydroxyvitamin D₃), as well as the numerous natural and synthetic Vitamin D analogs set forth, for example, in Bouillon et al. (Endocrine Reviews, 16:200 257,1995). Vitamin D drugs also include Vitamin D preparations and analogs that are currently in clinical use, such as Rocaltrol® (Roche Laboratories), Calcijex® injectable calcitriol, investigational drugs from Leo Pharmaceutical including EB 1089 (24a,26a,27a-trihomo-22,24-diene-lαa,25-(OH)₂- D₃), KH 1060 (20-epi-22-oxa-24a,26a,27a-trihomo-lα,25-(OH)₂-D₃), MC 1288 and MC 903 (calcipotriol), Roche Pharmaceutical drugs that include l,25-(OH)₂-16-ene-D₃, l,25-(OH)₂-16-ene- 23-yne-D₃, and 25-(OH)₂-16-ene-23-yne-D₃, Chugai Pharmaceuticals 22-oxacalcitriol (22-oxa-lα,25- (OH)2-D₃; lα-(OH)D₅ from the University of Illinois; and drugs from the Institute of Medical

Chemistry-Schering AG that include ZK 161422 and ZK 157202. Vitamin D analogs also include topical preparations of Vitamin D, such as Calcipotriene (Dovonex) and Tacalcitol, used in the treatment of psoriasis. Vitamin D drugs and their uses are further disclosed in U.S. Pat. No. 6,521,608, which is herein incorporated by reference. A "pulse dose" of a Vitamin D drug refers to administration of the drug in a sufficient amount to increase the blood or tissue level of Vitamin D to a supraphysiologic concentration for a sufficient period of time to have a therapeutic benefit, but with a sufficient period between doses to avoid hypercalcemia, given the pharmacological half life of the drug, its rate of elimination from the body, and its calcemic index. Vitamin D receptor (or VDR): A protein transcription factor, for which the gene and its product have already been characterized and found to contain 427 amino acids, with a molecular weight of about 47,000, or variants thereof. The full length cDNA of the human VDR is disclosed in Baker et al. (Proc. Natl. Acad. Sci. USA, 85:3294-3298, 1988). A "neoplasm that expresses (or contains) the Vitamin D receptor" includes tumors that have been shown to contain the Vitamin D receptor, tumors that are subsequently shown to contain the receptor (using immunohistochemical or other techniques), tumor types (such as breast cancer) that have demonstrated a clinical improvement in response to treatment with calcitriol or its analogs or other Vitamin D drugs, and tumors for which there is epidemiologic data demonstrating an association between low Vitamin D levels and higher cancer incidence (such as adenocarcinomas of the prostate, breast and colorectum). The presence of Vitamin D receptors can be determined by any means known in the art, such as any of the techniques disclosed in Pike, Ann. Rev. Nut, 11:189-216, 1991.

Unless otherwise explained, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. The singular terms "a," "an," and "the" include plural referents unless context clearly indicates otherwise. Similarly, the word "or" is intended to include "and" unless the context clearly indicates otherwise. "Comprising" means "including." Hence "comprising A or B" means "including A or B" or "including A and B." It is further to be understood that all base sizes or amino acid sizes, and all molecular weight or molecular mass values, given for nucleic acids or polypeptides are approximate, and are provided for description. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described below. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification, including explanations of terms, will control. The materials, methods, and examples described herein are illustrative only and not intended to be limiting. Other useful methods and techniques are well known in the art and are described in various general and more specific references. See, e.g., Sambrook et al, Molecular Cloning: A Laboratory Manual, 2d ed., Cold Spring Harbor Laboratory Press, 1989; Sambrook et al, Molecular Cloning: A Laboratory Manual, 3d ed., Cold Spring Harbor Press, 2001 ; Ausubel et al, Current Protocols in Molecular Biology, Greene Publishing Associates, 1992 (and Supplements to 2000); Ausubel et al, Short Protocols in Molecular Biology: A Compendium of Methods from Current Protocols in Molecular Biology, 4th ed., Wiley & Sons, 1999; Harlow and Lane, Antibodies: A Laboratory Manual, Cold Spring Harbor Laboratory Press, 1990; and Harlow and Lane, Using Antibodies: A Laboratory Manual, Cold Spring Harbor Laboratory Press, 1999.

HI. Inhibition oflRXS Activity This disclosure reveals that inhibition of IRX5 activity, at least, results in suppression of cell growth and apoptosis. IRX5 is expressed in neoplastic cells, such as prostate tumors. Thus, inhibition of IRX5 has important therapeutic uses; for example, IRX5 inhibitors can be used to treat hyperproliferative disorders (such as, neoplasia) and/or induce apoptosis in hyperproliferative (for example, neoplastic) cells. IRX5 activity may be inhibited at any point in the progression from activation of transcription of the IRX5 gene, transcription of the IRX5 gene, post-transcriptional message processing, translation of IRX5 mRNA(s), post-translational protein processing, to IRX5 protein activity, or modulating the activity of one or more downstream IRX5 targets (such as, p21, p53, Mdm2, Gadd45, Rb, or Mashl). Moreover, any agent capable of inhibiting an IRX5 activity is contemplated by this disclosure, such agents may include for example, small molecules, drugs, chemicals, compounds, siRNA, shRNAs, ribozymes, anti-sense oligonucleotides, IRX5 inhibitory antibodies, IRX5 inhibitory peptides (such as, IRX5 peptide fragments), aptamers, or mirror-image aptamers. 1. Inhibition ofIRX5 Nucleic Acids In some embodiments, the expression of the IRX5 gene may be inhibited, for example, by targeting or manipulating trans-acting activators or silencers of IRX5 genomic sequences. In specific examples, trans-acting activators (such as Hoxb4) may be prohibited from binding to their cis-acting elements in the IRX5 regulatory sequence, or the binding of trans-acting silencers to their cognate sites in the IRX5 regulatory sequence may be promoted or enhanced; in either event, resulting in suppression or inhibition of IRX5 gene expression. Alternatively, transcription of the IRX5 gene may be completely or partially inhibited by specific silencing of the gene by DNA methylation (see, for example, U.S. Pat. No. 5,840,497), by inhibition of the nuclear enzyme histone deacetylase (see, for example, U.S. Pat. No. 6,495,719), or through the use of gene promoter-suppressing nucleic acids (such as, Utrons) as described in U.S. Pat. No. 6,022,863. In other embodiments, IRX5 gene expression may be inhibited by interfering with IRX5 mRNA transcription, processing or translation, for example, using siRNA, shRNAs, ribozymes or anti-sense oligonucleotides, as described in the following subsections, a. siRNA Expression of IRX5 can be reduced using small inhibitory RNAs, for instance using techniques similar to those described previously (see, e.g., Fire et al, Nature, 391:806-811, 1998; Hamilton and Baulcombe, Science, 286:950-952, 1999; Tuschl et al, Genes Dev., 13:3191-3197, 1999; Zamore et al, Cell, 101:25-33, 2000; Caplen et al, Proc. Natl. Acad. Sci., 98:9742-9747, 2001; Elbashir et al, Nature, 411:494-498, 2001; Myers et al, Nat. BiotechnoL, 21:325-328, 2003; U.S. Pat. No. 6,506,559). Short interfering RNA (siRNA) is an intermediate in the RNAi process in which relatively longer double-stranded RNA is cut up into relatively shorter double-stranded RNA. The siRNA stimulates the cellular machinery to cut up other single-stranded RNA having the same sequence as the siRNA. siRNAs can induce gene-specific inhibition of expression in invertebrate and vertebrate species. These RNAs are suitable for interference or inhibition of expression of a target gene (such as, the IRX5 gene) and comprise double stranded RNAs of about 15 to about 40 nucleotides, optionally, containing a 3' and/or 5' overhang on each strand having a length of 0 to about 5 nucleotides, wherein the sequence of the double stranded RNAs is substantially identical (for example, at least 90%, at least 95%, at least 98%, or even 100% identical) to a portion of a mRNA or transcript of the target gene for which interference or inhibition of expression is desired, such as the IRX5 mRNA. The double stranded RNAs can be formed from complementary ssRNAs or from a single-stranded RNA that forms a hairpin (shRNA) or from expression from a DNA vector. In some examples, a siRNA sequence has ~50% G or C nucleotides, no homology in the sequence database to genes other than the intended target and no run of identical nucleotides. In specific embodiments, siRNA duplexes are composed of 20- to 22-nucleotide sense and corresponding 20- to 22-nucleotide antisense strands. In some instances, such sense and antisense strands are paired to have a 3' overhang of 2 nucleotides. In a preferred embodiment, the siRNA duplexes are composed of 21 -nucleotide sense and 21 -nucleotide antisense strands, which are paired to have a 3' overhang of 2 nucleotides. In some examples, 2'-deoxynucleotides may be used to form the 3' overhangs. 2'-deoxynucleotides are typically as efficient as ribonucleotides and have the advantage of being less expensive to synthesize and may be more nuclease resistant. In specific embodiments, siRNA sequences include a TT in the 3 '-overhang. The region to be targeted by a siRNA (such as an IRX5-specific siRNA) can be selected from any portion of a given mRNA sequence, such as the 5'-UTR, the coding sequence (ORF), or the 3'-UTR. In some embodiments, the siRNA target sequence is selected from the ORF. In more specific embodiments, the siRNA target sequence is selected from the ORF beginning 50 to 100 nucleotides downstream of the start codon. In other embodiments the siRNA target sequence is selected from the 3'-UTR. Non-limiting IRX5 siRNA target sequences (and or sense strands) are or include the sequences shown in SEQ ID NOs: 5, 6, 8, 9, 11, 12 or 17-108. In one embodiment, it is useful to search for a 23 -nucleotide sequence motif AA(N19)TT (N, any nucleotide) and select hits with about 30%-70% G/C content, such as about 50% G/C content. Having discovered the benefits of inhibiting the expression of a particular gene (such as, IRX5), various tools for designing siRNA (or shRNAs) for the inhibition of that target gene are readily available and known to those of ordinary skill in the art (see, e.g., siRNA target finders available from Ambion, Genscript, Invitrogen, Dharmacon, the Bioinformatics group of the Whitehead Institute for Biomedical Research, and many others). Methods of annealing the sense and antisense strands of a siRNA are known in the art. In one sample method, 20 μM of single-stranded 21 -nucleotide RNAs are combined in annealing buffer (100 mM potassium acetate, 30 mM HEPES-KOH at pH 7.4, 2 mM magnesium acetate) for 1 minute at 90°C, followed by 1 hour at 37°C. The solution can be stored frozen at -20°C and, optionally, freeze-thawed many times. Synthetic hairpin RNAs (shRNAs) can substitute for siRNAs duplexes (see, for example, Harborth et al, Antisense Nuc. Acid Drug Dev., 13(2):83-105, 2003). Representative shRNAs are shown in SEQ ID NOs: 117-138. In addition to native RNA molecules, RNAs suitable for inhibiting or interfering with the expression of a target sequence include RNA derivatives and analogs. For example, a non-natural linkage between nucleotide residues can be used, such as a phosphorothioate linkage. The RNA strand can be derivatized with a reactive functional group or a reporter group, such as a fluorophore. Particularly useful derivatives are modified at a terminus or termini of an RNA strand, typically the 3' terminus of the sense strand. For example, the 2'-hydroxyl at the 3' terminus can be readily and selectively derivatized with a variety of groups. Other useful RNA derivatives incorporate nucleotides having modified carbohydrate moieties, such as 2'-0-alkylated residues or 2'-deoxy-2'-halogenated derivatives. Particular examples of such carbohydrate moieties include 2 '-O-methyl ribosyl derivatives and 2'-0-fiuoro ribosyl derivatives. The RNA bases may also be modified. Any modified base useful for inhibiting or interfering with the expression of a target sequence can be used. For example, halogenated bases, such as 5-bromouracil and 5-iodouracil can be incorporated. The bases can also be alkylated, for example, 7-methylguanosine can be incorporated in place of a guanosine residue. Non-natural bases that yield successful inhibition can also be incorporated. Table 1 shows some non-limiting representative siRNA and shRNA sequences and the start location in the IRX5 mRNA (see, SEQ ID NO: 1 or 3, where T equals U). Each siRNA sense strand shown in Table 1 may include two 3' dT nucleotides. The corresponding antisense strand for each of the indicated siRNAs is the complement of the sense strand (and also may contain two 3'dJ nucleotides). Table 1. Non-limiting IRX5-specific siRNA and shRNA

b. Ribozymes Also contemplated herein are ribozymes, which are gene-targeting agents useful for specific inhibition of gene expression (see, e.g., Zamecnik and Stephenson, Proc. Natl Acad. Sci., 75:280-284, 1978; Airman, Proc. Natl. Acad. Sci., 90:10898-10900, 1993; Rossi, Chem. Biol, 6:R33-R37, 1999; Trang et al, Proc. Natl Acad. Sci., 97:5812-5817, 2000), such as inhibition of IRX5 gene expression. The production and use of ribozymes are disclosed in U.S. Patent No. 4,987,071 to Cech and U.S. Patent No. 5,543,508 to Haselhoff. Further, RNA enzymes capable of cleaving specific substrate RNA are known in the art, including, for instance, the hairpin (Hampel et al, Nucleic Acids Res., 18:299-304, 1990; Yu et al, Proc. Natl. Acad. Sci., 90:6340-6344,1993), the hammerhead (Forster and Symons, Cell, 50:9-16, 1987; Uhlenbeck, Nature, 328:596-600, 1987; Cantor et al, Proc. Natl. Acad. Sci., 90:10932-10936, 1993), the axehead (Branch and Robertson, Proc. Natl. Acad. Sci., 88:10163-10167, 1991), the group I intron (Hampel et al, Nucleic Acids Res., 18:299-304, 1990), and RNase P (Yuan et al, Proc. Natl. Acad. Sci., 89:8006-8010, 1992). The substrate-binding region of RNA enzymes may be modified, using methods well known in the art, to be complementary to a portion of a target RNA, such as IRX5 mRNA. When delivered to cells expressing the target RNA, the RNA enzyme will then form a complex with and cleave the target RNA. The target-specific ribozyme may then dissociate from the cleaved substrate RNA, and repeatedly hybridize to and cleave additional substrate RNA molecules; ultimately, inhibiting the expression and activity of any protein encoded by the target RNA. The nucleic acid sequence of the IRX5 mRNA is known (SEQ ID NO: 1 or 3, wherein T equals U). Thus, a ribozyme useful for specifically cleaving IRX5 mRNA may be designed by selecting, for example, at least 5, at least 10, at least 15, at least 20, at least 30 consecutive nucleotides of IRX5 mRNA(s) as a substrate for IRX5-specific ribozyme cleavage, c. Anti-sense Oligonucleotides The methods disclosed herein further contemplate a reduction of IRX5 activity in vitro or in vivo by introducing into cells, such as neoplastic cells, an anti-sense construct based on the IRX5-encoding sequence, including the cDNA sequence of IRX5 (SEQ ID NO: 1 or 3) or flanking regions thereof. For anti-sense suppression, a nucleotide sequence from an IRX5-encoding sequence, for example all or a portion of the IRX5 cDNA, is arranged in reverse orientation relative to the promoter sequence in the transformation vector. The introduced sequence need not be a full-length IRX5 cDNA or gene or reverse complement thereof, and need not be exactly homologous to the equivalent sequence found in the cell type to be transformed. Generally, however, where the introduced sequence is of shorter length, a higher degree of homology to the native IRX5 sequence will be needed for effective anti-sense suppression. The introduced anti-sense sequence in the vector may be at least 30 nucleotides in length, and improved anti-sense suppression will typically be observed as the length of the anti-sense sequence increases. The length of the anti-sense sequence in the vector advantageously may be greater than 100 nucleotides. For suppression of the IRX5 gene itself, transcription of an anti-sense construct results in the production of RNA molecules that are the reverse complement of mRNA molecules transcribed from the endogenous IRX5 gene in the cell. In one method embodiment, anti-sense phosphorothioate chimeric oligonucleotides (PSC-oligos) can be used to specifically decrease IRX5 expression in cells, such as prostate cancer cells. PSC-oligos are useful for anti-sense treatment because of their long term stability in cells, increased target specificity, and low toxicity (for example, LD50 in mice is 500 mg/kg, while effective doses occur at 5-10 mg/ml) (see, e.g., Agrawal and Zhao, Curr. Opin. Chem. Biol, 2(4):519-528, 1998). One representative method useful for identifying IRX5 anti-sense phosphorothioate chimeric oligonucleotides (PSC-oligos) is described below. RNAseH is a nuclease that recognizes and specifically degrades the RNA strand in an RNA:DNA duplex. RNAseH mapping can identify DNA oligonucleotides that anneal to a target RNA (see, e.g., Ho et al, Nucleic Acids Res., 24(10): 1901-1907, 1996). Briefly, the procedure involves using a defined RNA (such as, IRX5 RNA), which can be produced in vitro, as a target to identify those oligonucleotides that specifically bind the target RNA (for example, IRX5 RNA) from a pool of oligonucleotides (also referred to as an oligonucleotide library). A reverse phase HPLC purified random library of PSC-oligos of defined length is produced using a mixture of phosphoramidates to synthesize oligonucleotides (Touleme et al, Prog. Nucleic Acid Res. Mol. Biol, 69:1-46, 2001). A full-length IRX5 RNA target is synthesized using a large-scale in vitro transcription assay and purified using methods known in the art. The IRX5 RNA and random PSC-oligo library are mixed and allowed to hybridize under conditions empirically determined to allow specific interactions as described in Ho et al. (Nucleic Acids Res., 24(10):1901- 1907, 1996). Then, RNAseH is added to the RNA/oligonucleotide mixture and the digestion reaction proceeds for approximately 30 minutes. The reaction is stopped by the addition of RNAse inhibitors and EDTA, and the resulting RNA fragments are reverse transcribed into corresponding cDNA fragments using several different C-terminal IRX5-specifϊc primers. This results in a population of cDNAs having the 5' end of each molecule specific for a primer sequence that mediated in vitro RNAse cleavage. The cDNA fragments are separated on a denaturing polyacrylamide gel. A sequencing gel of the full-length IRX5 cDNA using the same primer is also produced. The sequences of anti-sense PSC-oligos that specifically bind IRX5 RNA is determined by observing where the bands line up on the two gels. PSC-oligos identified in this example may be used to inhibit in vitro and in vivo IRX5 gene expression. d. Oligonucleotide Synthesis Oligonucleotides, such as single-stranded DNA or RNA oligonucleotides, including, for example, aptamers or anti-sense oligonucleotides, often are synthesized by chemical methods, such as those implemented on automated oligonucleotide synthesizers. However, oligonucleotides can be made by a variety of other methods, including in vitro recombinant DNA-mediated techniques and by expression of DNAs in cells and organisms. Initially, chemically synthesized DNAs typically are obtained without a 5' phosphate. The 5' ends of such oligonucleotides are not substrates for phosphodiester bond formation by ligation reactions that employ DNA ligases typically used to form recombinant DNA molecules. Where ligation of such oligonucleotides is desired, a phosphate can be added by standard techniques, such as those that employ a kinase and ATP. The 3' end of a chemically synthesized oligonucleotide generally has a free hydroxyl group and, in the presence of a ligase, such as T4 DNA ligase, readily will form a phosphodiester bond with a 5' phosphate of another polynucleotide, such as another oligonucleotide. As is well known, this reaction can be prevented selectively, where desired, by removing the 5' phosphates of the other polynucleotide(s) prior to ligation.

2. Inhibition oflRX5 PolvpeptideCs) Certain methods disclosed herein contemplate inhibition of IRX5 polypeptides by, for example, IRX5 inhibitory antibodies, IRX5 inhibitory peptides (such as, IRX5 peptide fragments), aptamers or mirror-image aptamers. a. Inhibitory Antibodies Antibodies that inhibit IRX5 activity may be monoclonal or polyclonal; though, monoclonal inhibitory antibodies are preferred. Monoclonal or polyclonal antibodies may be produced to specifically recognize and bind an IRX5 protein (SEQ ID NO: 2 or 4) or fragments thereof as a first step in producing IRX5 inhibitory antibodies. Optimally, antibodies raised against these proteins or peptides would specifically detect the protein or peptide with which the antibodies are generated. That is, an antibody generated to an IRX5 protein or a fragment thereof would recognize and bind IRX5 and preferably would not substantially recognize or bind to other proteins found in target cells. The determination that an antibody specifically detects an IRX5 protein is made by any one of a number of standard immunoassay methods; for instance, the Western blotting technique (Sambrook et al, Molecular Cloning: A Laboratory Manual, New York: Cold Spring Harbor Laboratory Press, 1989). IRX5-specific antibodies may be screened for those that inhibit IRX5 activity as described in additional detail below. Monoclonal or polyclonal antibody to the protein can be prepared, for example, using any of the detailed procedures described in Harlow and Lane (Antibodies, A Laboratory Manual, New York: Cold Spring Harbor Laboratory Press, 1988). In specific examples, a monoclonal antibody to an epitope of the IRX5 protein identified can be prepared from murine hybridomas according to the classical method of Kohler and Milstein (Nature, 256:495-497, 1975) or derivative methods thereof. For administration to human subjects, IRX5-specific inhibitory antibodies can be humanized by methods known in the art. Antibodies with a desired binding specificity can be commercially humanized (see, for example, Scotgene, Scotland, UK; Oxford Molecular, Palo Alto, CA). b. Inhibitory Peptides Some method embodiments disclosed herein contemplate polypeptide or peptide agents that measurably reduce at least one biological activity of IRX5, for example peptides that can inhibit an IRX5 activity. Inhibitory peptides are typically less than about 250 amino acid residues in length, for example, less than about 200 amino acid residues, less than about 150 amino acid residues, less than about 100 amino acid residues, less than about 75 amino acid residues, less than about 50 amino acid residues, less than about 40 amino acid residues, or less than about 30 amino acid residues in length. Peptides may be screened for those that inhibit IRX5 activity as described in additional detail below. In some embodiments, inhibitory peptides are dominant negative fragments of the IRX5 polypeptide. c. Specific-binding Oligonucleotides (Aptamers and Mirror-image Aptamers") Specific-binding oligonucleotides (such as, aptamers and mirror-image aptamers (a.k.a.,

Spiegelmers™)) are oligonucleotides with high affinity and high specificity for a wide variety of target molecules (as reviewed in Jayasena, Clin. Chem., 45(9):1628-1650, 1999), including, for example, polypeptides, peptides, metal ions, organic dyes, drugs, amino acids, cofactors, nucleotides, antibiotics, nucleotide base analogs, and aminoglycosides. In particular examples, a specific-binding oligonucleotide binds to an IRX5 polypeptide and inhibits its activity. Specific-binding oligonucleotides for a particular target are typically selected from a large "library" of unique nucleic acid molecules (often as many as 10¹⁴-10¹⁵ different compounds or more). Each oligonucleotide molecule in the library contains a unique nucleotide sequence that can, in principle, adopt a unique three-dimensional shape. The target-specific oligonucleotides are thought to present a surface that is complementary to the target molecule. Chemically modified oligonucleotides may be included in oligonucleotide libraries, for example, 2,6-diaminopyrimidine, xanthine, 2,4-difluorotoluene, 6-methylpurine, 5-(l-pentynyl-2-deoxyuridine), pyrimidines modified with 2'-NH₂ and 2'-F functional groups. The library of nucleotide sequences is exposed to the target (such as, a protein, small molecule, or supramolecular structure) and allowed to incubate for a period of time. Where a mirror-image aptamer (commonly known as a Spiegelmer) is the desired product, the oligonucleotide library is exposed to an enantiomeric form of the natural target. The molecules in the library with weak or no affinity for the target will, on average, remain free in solution while those with some capacity to bind will tend to associate with the target. The specific oligonucleotide/target complexes are then separated from the unbound molecules in the mixture by any of several methods known in the art. Target-bound oligonucleotides are separated and amplified using common molecular biology techniques to generate a new library of oligonucleotide molecules that is substantially enriched for those that can bind to the target. The enriched library is used to initiate a new cycle of selection, partitioning and amplification. After several cycles (such as, 5-15 cycles) of the complete process, the library of oligonucleotide molecules is reduced from 10¹⁴-10¹⁵ or more unique sequences to a small number that bind tightly to the target of interest. Individual oligonucleotide molecules in the mixture are then isolated, and their nucleotide sequences are determined. In most cases, isolated target-specific oligonucleotides are further refined to eliminate any nucleotides that do not contribute to target binding or oligonucleotide structure. Target-specific oligonucleotides (referred to as aptamers) truncated to their core binding domain typically range in length from 15 to 60 nucleotides. Once a sequence is identified, the target-specific oligonucleotide may be prepared by any known method, including synthetic, recombinant, and purification methods. Any one target-specific oligonucleotide may be used alone or in combination with other oligonucleotides specific for the same target. Where an enantiomeric form of the target was combined with the library, as discussed above, the L-form of the isolated oligonucleotide sequence(s) is synthesized to generate a mirror- image aptamer, which is specific for the naturally occurring target. Representative methods of making aptamers specific for non-DNA-binding proteins are described, for example, in U.S. Pat. No. 5,840,867, and in Jayasena, Clin. Chem., 45(9): 1628-1650, 1999. IRX5-specific aptamers or mirror-image aptamers may be screened for those that inhibit IRX5 activity, as described in additional detail below.

IV. Antiproliferative Uses oflRXS Inhibitory Agents IRX5 inhibitory agents (such as, IRX5-specific siRNAs and shRNAs) have been shown herein to be potent suppressors of cell growth. For example, one representative class of IRX5 inhibitory agents, IRX5-specific siRNAs, have been shown to effectively induce treated cells to undergo apoptosis. Thus, methods of using IRX5 inhibitory agent(s) for the treatment of hyperproliferative disorders (such as, neoplasia) in which one or more hyperproliferative cells (such as, neoplastic cells) express IRX5 mRNA or polypeptide are now available. Neoplasia includes any biological condition in which one or more cells have undergone characteristic anaplasia with loss of differentiation and increased rate of growth. Neoplasia, which may be treated by the disclosed IRX5 inhibitory agents, includes breast carcinomas (e.g. lobular and duct carcinomas), and other solid tumors, sarcomas, and carcinomas of the lung like small cell carcinoma, large cell carcinoma, squamous carcinoma, and adenocarcinoma, mesothelioma of the lung, colorectal adenocarcinoma, stomach carcinoma, prostatic adenocarcinoma, ovarian carcinoma such as serous cystadenocarcinoma and mucinous cystadenocarcinoma, ovarian germ cell tumors, testicular carcinomas, and germ cell tumors, pancreatic adenocarcinoma, biliary adenocarcinoma, heptacellular carcinoma, bladder carcinoma including transitional cell carcinoma, adenocarcinoma, and squamous carcinoma, renal cell adenocarcinoma, endometrial carcinomas including adenocarcinomas and mixed Mullerian tumors (carcinosarcomas), carcinomas of the endocervix, ectocervix, and vagina such as adenocarcinoma and squamous carcinoma, tumors of the skin like squamous cell carcinoma, basal cell carcinoma, melanoma, and skin appendage tumors, esophageal carcinoma, carcinomas of the nasopharynx and oropharynx including squamous carcinoma and adenocarcinomas, salivary gland carcinomas, brain and central nervous system tumors including tumors of glial, neuronal, and meningeal origin, tumors of peripheral nerve, soft tissue sarcomas and sarcomas of bone and cartilage. Also included are non-solid hematopoietic tumors, such as including acute leukemias (such as acute lymphocytic leukemia, acute myelocytic leukemia, acute myelogenous leukemia and myeloblastic, promyelocytic, myelomonocytic, monocytic and erytliroleukemia), chronic leukemias (such as chronic myelocytic (granulocytic) leukemia, chronic myelogenous leukemia, and chronic lymphocytic leukemia), polycythemia vera, lymphoma, Hodgkin's disease, non-Hodgkin's lymphoma (indolent and high grade forms), multiple myeloma, Waldenstrom's macroglobulinemia, heavy chain disease, myelodysplastic syndrome, and myelodysplasia. In one embodiment, an IRX5 inhibitory agent, for example, introduced by intraperitoneal or intravenous injection, can be used to treat prostate cancers, such as prostate adenocarcinoma. The antiproliferative effects of an IRX5 inhibitory agent may, in some embodiments, be mediated, at least in part, by apoptosis of the treated cells. In such examples, an IRX5 inhibitory agent may, over a course of treatment, induce apoptosis in at least 5%, at least 10%, at least 15%>, at least 25%, at least 50%, at least 70%, at least 80%, at least 90% or even more of the treated cell population. In such examples, at any one point in time, between about 0.5%> to about 25% of the treated cell population (for example, between about 1% to about 20%, or between about 5% to about 15%)) may be actively undergoing apoptosis. Apoptosis can be measured by any of the many methods known in the art. V. Screening for Agents that Inhibit an IRX5 Activity Described herein are methods for identifying agents with IRX5 inhibitory activity. Such agents may be useful as therapeutics for treating hyperproliferative disorders, such as neoplasms, including, for example, prostate cancer. Any agent that has potential (whether or not ultimately realized) to directly or indirectly inhibit IRX5 expression and/or activity is contemplated for use in the screening methods of this disclosure. Exemplary compounds that maybe screened in accordance with this disclosure include, but are not limited to, siRNAs, shRNAs, other nucleic acids (including, for example, any nucleic acid involved in an IRX5 RNAi system, or oligonucleotides or anti-sense oligonucleotides), small molecules, polypeptides, peptides, antibodies and fragments thereof, drugs, chemicals, organic compounds (for example, peptidomimetics, small molecules), inorganic compounds, or other compounds that inhibit IRX5 activity as described herein. Agents that specifically inhibit IRX5 function may include; for example, agents that directly and specifically bind to IRX5 mRNA or protein. In particular examples, compounds that can be evaluated by the disclosed screening methods include small molecules (such as, small organic molecules) that are able to gain entry into an appropriate cell and affect the expression of IRX5 genes or some other gene involved in an IRX5-mediated pathway (for example, by interacting with the regulatory region or transcription factors involved in IRX5 gene expression); peptides, such as, soluble peptides, including members of random peptide libraries; (see, e.g., Lam et aL, Nature, 354:82-84, 1991; Houghten et al, Nature, 354:84-86, 1991), and combinatorial chemistry-derived molecular library made of D- and/or L-configuration amino acids, phosphopeptides (including, but not limited to, members of random or partially degenerate, directed phosphopeptide libraries; see, e.g., Songyang et al, Cell, 72:767-778, 1993); antibodies (including, but not limited to, polyclonal, monoclonal, humanized, anti-idiotypic, chimeric or single chain antibodies, and Fab, F(ab')₂ and Fab expression library fragments, and epitope-bindrng fragments thereof). Some method embodiments permit high-throughput screening of large numbers of candidate agents in order to identify those agents that specifically bind to an IRX5 target and/or inhibit expression or an activity of an IRX5 target. Libraries useful for the disclosed screening methods include, but are not limited to, spatially arrayed multipin peptide synthesis (Geysen, et al, Proc. Natl. Acad. Sci., 81(13):3998-4002, 1984), "tea bag" peptide synthesis (Houghten, Proc. Natl. Acad. Sci., 82(15):5131-5135, 1985), phage display (Scott and Smith, Science, 249:386-390, 1990), spot or disc synthesis (Dietrich et al, Bioorg. Med. Chem. Lett., 8(17):2351-2356, 1998), or split and mix solid phase synthesis on beads (Furka et al, Int. J. Pept. Protein Res., 37(6):487-493, 1991; Lam et al, Chem. Rev., 97(2):411-448, 1997). In one convenient embodiment, high throughput screening methods involve providing a combinatorial chemical or peptide library containing a large number of potential therapeutic compounds (potential inhibitor or specific binding compounds). Such combinatorial libraries are then screened in one or more assays as described herein, to identify those library members (such as, particular chemical species or subclasses) that display a desired characteristic activity (such as, specific binding to, or inhibiting an activity or expression of, IRX5). The compounds thus identified can serve as conventional "lead compounds" or can themselves be used as potential or actual therapeutics. A combinatorial library is a collection of diverse chemical compounds generated by either chemical synthesis or biological synthesis, by combining a number of chemical "building blocks" such as reagents. For example, a linear combinatorial chemical library such as a polypeptide library is formed by combining a set of chemical building blocks (amino acids) in every possible way for a given compound length (i.e., the number of amino acids in a polypeptide compound). Millions of chemical compounds can be synthesized through such combinatorial mixing of chemical building blocks. Preparation and screening of combinatorial chemical libraries is well known to those of skill in the art. Such combinatorial chemical libraries include, but are not limited to, peptide libraries (see, e.g., U.S. Patent 5,010,175; Furka, IntJPept Prot Res 37:487-493, 1991; and Houghton et al, Nature 354:84-88, 1991). Other chemistries for generating chemical diversity libraries can also be used. Such chemistries include, but are not limited to: peptides (e.g., PCT Publication No. WO 91/19735), encoded peptides (e.g. , PCT Publication WO 93/20242), random bio-oligomers (e.g. , PCT

Publication No. WO 92/00091), benzodiazepines (e.g., U.S. Pat. No. 5,288,514), diversomers such as hydantoins, benzodiazepines and dipeptides (Hobbs et al, PNAS USA 90:6909-6913, 1993), vinylogous polypeptides (Hagihara et al, J Amer Chem Soc 114:6568, 1992), nonpeptidal peptidomimetics with glucose scaffolding (Hirschmann et al, J Amer Chem Soc 114:9217-9218, 1992), analogous organic syntheses of small compound libraries (Chen et al, J Amer Chem Soc

116:2661, 1994), oligocarbamates (Cho et al 1993 Science 261:1303), and/or peptidyl phosphonates (Campbell et al, J Org Chem 59:658, 1994), nucleic acid libraries (see Sambrook et al. Molecular Cloning, A Laboratory Manual, Cold Springs Harbor Press, N.Y., 1989; and Ausubel et al. Current Protocols in Molecular Biology Green Publishing Associates and Wiley Interscience, N.Y., 1989), peptide nucleic acid libraries (see, e.g., U.S. Patent 5,539,083), antibody libraries (see, e.g., Vaughn etal Nature Biotechnology 14:309-314, 1996; and PCT/US96/10287), carbohydrate libraries (see, e.g., Liang et al, Science 274:1520-1522, 1996; and U.S. Patent 5,593,853), small organic molecule libraries (see, e.g., benzodiazepines, Baum 1993 C&EN, Jan 18, page 33; isoprenoids, U.S. Patent 5,569,588; thiazolidionones and methathiazones, U.S. Patent 5,549,974; pyrrolidines, U.S. Patents 5,525,735 and 5,519,134; morpholino compounds, U.S. Patent 5,506,337; benzodiazepines, 5,288,514, and the like). Devices for the preparation of combinatorial libraries are commercially available (see, e.g., 357 MPS, 390 MPS, Advanced Chem Tech, Louisville, KY; Symphony, Rainin, Woburn, MA; 433A Applied Biosystems, Foster City, CA; 9050 Plus, Millipore, Bedford, MA). In addition, numerous combinatorial libraries are themselves commercially available (see, e.g., ComGenex, Princeton, N.J.; Tripos, Inc., St. Louis, MO; 3D Pharmaceuticals, Exton, PA; Martek Biosciences, Columbia, MD; etc). A combinatorial library can include at least 100, at least 1000, at least 5000, at least 10,000, at least 25,000, at least 100,000, at least 250,000 or even more members. Screening methods may include, but are not limited to, methods employing solid phase, liquid phase, cell-based or virtual (in silico) screening assays. Some representative screening assays involve identifying compounds that interact with (e.g., specifically bind to) an IRX5 protein, IRX5 transcript, or variant or fragment of either (collectively or individually, 'TRX5 target"), or compounds that inhibit the expression and/or an activity of an IRX5 target. Assays may additionally be utilized which identify compounds that bind to IRX5 gene regulatory sequences (e.g., promoter sequences) and which may modulate IRX5 gene expression. See, e.g., Platt, J Biol Chem 269:28558-28562, 1994. Compounds identified via assays such as those described herein may be useful, for example, as drugs useful in the treatment of hyperproliferative disease (such as, prostate cancer), or to design and/or further identify such drugs. 1. Agents that Specifically Bind to IRX5 Targets Although not bound by theory, agents that specifically bind to an IRX5 target may, for example, inhibit an activity triggered by a natural ligand (i.e., antagonists), may act as a competitive inhibitor of a natural substrate or co-factor, or may disrupt or otherwise interfere with a protein-protein interaction (or protein complex) in which an IRX5 target is involved. The basic principle of assays used to identify agents that bind to IRX5 targets involves contacting such target with a test agent under conditions and for a time sufficient to allow the two components to interact and bind, thus forming a complex which can be detected. In some instances, an agent that selectively binds to an IRX5 target is selected for further testing for its ability to inhibit or treat at least one symptom of a hyperproliferative disease (such as, prostate cancer). Disclosed binding assays can be conducted in a variety of ways. For example, one method to conduct such an assay would involve anchoring one or more IRX5 targets or test substances onto a solid phase and detecting target/test compound complexes anchored on the solid phase at the end of the reaction. In one embodiment of such a method, an IRX5 target may be anchored onto a solid surface (such as, a microarray or in a microtitre plate), and the test compound, which is not anchored, may be labeled, either directly or indirectly. In another embodiment, a plurality of test compounds are attached to the support (for example, in an array or microplate format) and one or more detectable (e.g, labeled) IRX5 targets are applied to the solid support. In particular embodiments, at least 2, at least 5, at least 10, or at least 15 IRX5 targets are attached to a solid support. Each of the plurality of IRX5 targets may be present on the solid support in one or more addressable positions. Similarly, a plurality of test compounds maybe attached to a solid support, such as at least 25, at least 100, at least 250, at least 500, at least 1000, or at least 2500 test compounds, and each of the plurality of test compounds may be present on the solid support in one or more addressable positions. In one example method, mixtures of labeled compounds, for instance radiolabeled or fluorescently labeled compounds (such as, ¹⁴C-labeled compounds) can be tested for specific binding to isolated target molecules, such as one or more IRX5 targets (e.g., IRX5 protein or mRNA). Substantially purified target molecules are adsorbed onto a solid support (such as, a microarray or in microtiter wells), which may be subsequently blocked with an irrelevant protein, such as casein. Labeled test compounds, such as compounds in one or more of the above-described libraries, are separately added to a solid support (e.g., individual microtitre wells or microarray) containing the target molecule. Combinations of labeled compounds can be evaluated in an initial screen to identify pools of candidate agents to be tested individually. This process is easily automated with currently available technology. The reactions are incubated for a time sufficient to permit interaction between the target molecule and the labeled compounds. The solid support (e.g., microtiter wells or microarray) is washed and the amount of label (such as, radioactivity or fluorescence) measured in the washed wells. Agents that bind the target molecule (such as an IRX5 target) are identified by the presence of the greater-than-control levels of label (for instance, radioactivity or fluorescence) present on the solid surface (e.g., in a microtiter well). Agents that bind a target molecule are, optionally, isolated and tested in further assays (such as, functional assays) for their ability to inhibit and/or treat at least one symptom of a hyperproliferative disorder (such as, prostate cancer). Other analogous approaches using beads as a solid support or solution-phase screening (e.g., Boger et al, Angew. Chem. Int. Ed. EngL, 42:4138-4176, 1998; Cheng et al, Bioorg. Med. Chem., 4(5):727-737, 1996) can also be used in this approach. Briefly, in a solution-phase binding reaction, the target (such as, an IRX5 polypeptide or mRNA) and a test agent are mixed in solution. Under these circumstances, the target can be purified or present in a mixture of other components, such as in an organ, tissue, or cell extract. Small volumes (such as, in wells of a microtitre plate) can be used to promote high-throughput screening. After a period of time to permit binding of an agent to the target, the bound complex is separated from unbound components, and the complexes detected. One useful way to separate a bound complex is to use a first antibody specific for one or the other of the bound components (such as, an antibody against an IRX5 target (such as, IRX5 protein) or the test compound). The antibody may be bound to a solid support or may be sufficiently large to be separated from other components by centrifugation. A detectable second antibody specific for the bound complex (or the first antibody) is one exemplary method for detecting the separated complex. In this type of assay, the target (such as, an IRX5 polypeptide or mRNA) can be purified or present in a mixture of other components, such as in an organ, tissue, or cell extract. It is expected that different test agents will have different affinities for any one IRX5 target (such as, an IRX5 polypeptide or mRNA). Thus, in some methods, it is advantageous to test a range of test agent concentrations for binding properties. This technique is commonly known as a dilution series, and can be easily designed and performed by an ordinarily skilled artisan. 2. Agents that Inhibit the Expression and/or Activity of an IRX5 Target Also disclosed herein are methods of identifying agents that inhibit the expression and/or an activity of an IRX5 target (such as, an IRX5 gene, transcript or protein). Such methods can also be used to characterize IRX5 inhibitory properties (if any) of agents identified in binding assays.

Generally, methods of identifying agents that inhibit the expression and/or an activity of an IRX5 target involve contacting (directly or indirectly) an IRX5 target with a putative inhibitor, and detecting a decrease in the expression and/or an activity of the IRX5 target (such as, an IRX5 polypeptide or mRNA). "Putative inhibitors" as used herein include all agents (and libraries of agents) described above, including, for example, any agents identified in binding assays. Inhibition of the expression of an IRX5 gene or gene product (e.g., transcript or protein) can be determined using any system capable of expressing at least one such biological molecule (such as, a cell, tissue, or organism, or in vitro transcription or translation systems). In some embodiments, cell-based assays are performed. Non-limiting representative cell-based assays may involve test cells such as, cells (including cell lines) that normally express at an IRX5 gene and its corresponding transcript(s) and protein(s), or cells (including cell lines) that have been transiently transfected or stably transformed with a reporter construct driven by a regulatory sequence of an IRX5 gene. Exemplary cells (or tissues from which cells can be obtained) that normally express IRX5 at the transcript and/or protein level include LNCaP cells, MCF-7 breast cancer cells, and cells or tissue from prostate cancer, brain, lung, breast, or heart. Some disclosed methods involve cells (including cell lines) that have been transiently transfected or stably transformed with a reporter construct driven by a regulatory sequence of an IRX5 gene. A "regulatory sequence" as used herein can include some or all of the regulatory elements that regulate the expression of a particular nucleic acid sequence (such as, an IRX5 gene) under normal circumstances. In particular examples, a regulatory region includes the contiguous nucleotides located at least 100, at least 500, at least 1000, at least 2500, at least 5000, at least 7500, or at least 10,000 nucleotides upstream of the transcriptional start site of the regulated nucleic acid sequence (such as, an IRX5 gene). Up to 3000 nucleotides of a human IRX5 gene regulatory region can be obtained as provided in Example 10. In addition, a nucleic acid sequence of a human IRX5 gene regulatory region is provided in the publicly available sequence of the human chromsome 16 contig (GenBank Accession No. NT_010498; Version NT_010498.15; CON20-Aug-2004). In the human chromosome 16 contig, the IRX5 gene (including exons and introns) is located from residue 8579310 to residue 8582596. Accordingly, a nucleic acid sequence of an upstream (i.e., 5') regulatory region of the human IRX5 gene includes at least 100, at least 500, at least 1000, at least 2500, at least 5000, at least 7500, or at least 10,000 nucleotides upstream of residue 8579310 in GenBank Accession No. NT_010498. In one specific embodiment, Hox4b is a transcriptional regulator of the IRX5 gene regulatory region (e.g., Theokli et al, Dev. Dyn., 227:48-55, 2003). In specific embodiments, one or more test cells (such as a cell normally expressing an IRX5 gene or gene product, or a cell transiently or stably transfected with a reporter construct operably linked to an IRX5 gene regulatory region) are contacted with one or more agents, and a decrease in the expression (and/or activity, as discussed further below) of the IRX5 target is detected. Detection of a decrease in the expression of an IRX5 target is performed, for example, by measuring levels of IRX5 gene products (such as, RNA or protein) by standard techniques, such as, for RNA, Northern blot, PCR, or nucleic acid microarray, or, for protein, Western blot or antibody array. Alternatively, test cells can be examined to determine whether one or more cellular phenotypes have been altered in a manner consistent with inhibition of expression of an IRX5 target (including, e.g., onset of apoptosis, or inhibition of cell growth). In method embodiments involving a cell transiently or stably transfected with a reporter construct operably linked to an IRX5 gene regulatory region, the level of the reporter gene product can be measured (see, for instance, Example 10). Reporter genes are nucleic acid sequences that encode readily assayed proteins. Numerous reporter genes are commonly known and methods of their use are standard in the art. Non-limiting representative reporter genes are luciferase, β-galactosidase, chloramphenicol acetyl transferase, alkaline phosphatase, green fluorescent protein, and others. A decrease in the level and/or activity of reporter gene measured in cells in the presence or absence of a test agent indicates that the test agent inhibits the activity of the IRX5 regulatory region driving the reporter gene and, thereby, decreases IRX5 transcript and protein expression and any corresponding biological activity. Inhibition of an IRX5 transcript by a test agent can be determined, for example, by measuring levels of the transcript itself or a corresponding protein as described elsewhere in this specification. In some methods, a cell is contacted with a test agent by transfecting the cell with a vector capable of expressing the test agent. In a particular example, shRNA and/or siRNA expression vectors are transfected into test cells, and an inhibitory shRNA and/or siRNA is identified as one that decreases IRX5 transcript and/or protein levels. Methods of measuring IRX5 transcript and protein levels are described elsewhere in this specification. An "activity" of an IRX5 target can be any function of an IRX5 gene, transcript or protein described herein or as is commonly known in the art. For example, downregulation of IRX5 has been described herein to affect cell growth (e.g>, LNCaP) cell growth) and to be involved in apoptosis of, at least, prostate (e.g., LNCaP) cells. A putative IRX5 inhibitor can affect one or more activities of an IRX5 target, including any of the foregoing functions. Cell-based systems can be used to identify compounds that may act to inhibit IRX5 activity. One advantage in this approach is that the screen is not limited to a single defined property, but measures a biological response. Useful cell systems can include, for example, recombinant or non-recombinant cells, such as cell lines, which naturally express IRX5 (e.g., LNCaP or MCF-7 cells). In addition, expression host cells (e.g., COS cells, CHO cells, HEK293 cells) can be genetically engineered to express IRX5. In utilizing such cell systems, cells may be exposed to a putative inhibitor at a sufficient concentration (using, for example, a dilution series) and for a time sufficient to inhibit an IRX5 activity in the exposed cells. After exposure, treated and untreated cells can be examined to determine whether one or more cellular phenotypes have been altered in a manner consistent with inhibition of IRX5 activity (e.g., onset of apoptosis or inhibition of cell growth). In some cell-based method embodiments, test cells or test agents can be presented in a manner suitable for high-throughput screening; for example, one or a plurality of test cells expressing IRX5 can be seeded into wells of a microtitre plate, and one or a plurality of test agents can be added to the wells of the microtitre plate. Alternatively, one or a plurality of test agents can be presented in a high-throughput format, such as in wells of microtitre plate (either in solution or adhered to the surface of the plate), and contacted with IRX5-expressing test cells under conditions that, at least, sustain the test cells. Test agents can be added to test cells at any concentration that is not lethal to the cells. It is expected that different test agents will have different effective concentrations. Thus, in some methods, it is advantageous to test a range of test agent concentrations. As described herein, inhibition of IRX5, at least, results in suppression of cell growth; thus, for example, test cells are treated with one or more test compound(s), and the cell growth characteristics of the treated cells are measured. Agents that inhibit IRX5 activity are identified by suppression of the growth of the cells treated with such agent(s). Cell growth can be measured at any of a variety of times after exposure of test cells to a test agent, for example at 24, 48, 72 and 96 hours following addition of a test compound. In particular embodiments, the growth of cells exposed to a test agent is at least 25%, at least 50%, at least 70%, at least 80%, or at least 90% less than the growth of cells in the absence of the test agent. Cell growth can be measured by many methods known in the art, such as counting of cell number, incorporation of radiolabeled molecules, such as tritiated thymidine, or increases in mitochondrial activity. As also described herein, IRX5 inhibition results in cellular apoptosis; thus, in another example, test cells are treated with one or more test compound(s) and apoptosis of the treated cells (as compared to untreated cells) is measured. Agents that inhibit IRX5 activity are identified by the occurrence of apoptosis in at least some of the tested cells, for example, an IRX5 inhibitory agent may induce apoptosis in at least 5%, at least 10%, at least 15%, at least 25%, at least 50%, at least 70%, at least 80%, at least 90% or even more of the tested cells. At any one point in time following IRX5 inhibitor administration about 0.5% to about 25% of the treated cell population may be undergoing apoptosis; for example, between about 1% to about 20%, or between about 5% to about 15% of the treated cells. Apoptosis can be measured by any of the many methods known in the art. 3. Computer-based Assays Yet another assay for compounds that specifically bind to or inhibit the expression and/or activity of an IRX5 target (e.g., an IRX5 polypeptide) involves computer assisted drug design. In this type of assay, a computer system is used to generate a three-dimensional structure of IRX5 based on the structural information encoded by its amino acid sequence, or a known IRX5 protein structure is input into the computer system. The models of the protein structure are then examined to identify regions of the structure that have the ability to bind, e.g., ligands. These regions are then used to identify ligands that bind to the protein. The three-dimensional structural model of the protein can be generated by entering protein amino acid sequences of at least 10 amino acid residues or corresponding nucleic acid sequences encoding IRX5 into the computer system. The amino acid sequence represents a primary structure that encodes the information necessary to form the secondary, tertiary and quaternary structure of the protein of interest. The software looks at certain parameters encoded by the primary sequence to generate the structural model. These parameters are referred to as "energy terms," and primarily include electrostatic potentials, hydrophobic potentials, solvent accessible surfaces, and hydrogen bonding. Secondary energy terms include van der Walls potentials. Biological molecules form the structures that minimize the energy terms in a cumulative fashion. The computer program is therefore using these terms encoded by the primary structure or amino acid sequence to create the secondary structural model. The tertiary structure of the protein encoded by the secondary structure is then formed on the basis of the energy terms of the secondary structure. The user at this point can enter additional variables such as whether the protein is membrane bound or soluble, its location in the body, and its cellular location, e.g., cytoplasmic, surface, or nuclear. These variables along with the energy terms of the secondary structure are used to form the model of the tertiary structure. In modeling the tertiary structure, the computer program matches hydrophobic faces of secondary structure with like, and hydrophilic faces of secondary structure with like. Once the structure has been determined or, in the case of a known structure, entered into the computer, potential ligand binding regions are identified by the computer system. Three-dimensional structures for potential ligands are generated by entering amino acid or nucleotide sequences or chemical formulas of compounds, as described above. The potential ligand is then tested in a functional assay (described above) to determine whether can inhibit an IRX5 function. Examples of molecular modeling systems are the CHARMM and QUANTA programs

(Polygen Corporation, Waltham, Mass.). CHARMm performs the energy minimization and molecular dynamics functions. QUANTA performs the construction, graphic modeling and analysis of molecular structure. QUANTA allows interactive construction, modification, visualization, and analysis of the behavior of molecules with each other. A number of articles review computer modeling of drugs interactive with specific proteins, such as Rotivinen et al. Acta Pharmaceutical Fennica, 97:159-166, 1988; Ripka, New Scientist, 54- 57, 1988; McKinaly and Rossmann, Ann. Rev. Pharmacol. Toxicol, 29:111-122, 1989; Perry and Davies, OSAR: Quantitative Structure-Activity Relationships in Drug Design pp. 189-193, 1989 (Alan R. Liss, Inc.); Lewis and Dean, Proc. R. Soc. Lond., 236:125-140 and 141-162, 1989; and, with respect to a model receptor for nucleic acid components, Askew et al, J. Am. Chem. Soc,

111:1082-1090, 1989. Oilier computer programs that screen and graphically depict chemicals are available from companies such as BioDesign, Inc. (Pasadena, Calif.), Allelix, Inc. (Mississauga, Ontario, Canada), and Hypercube, Inc. (Cambridge, Ontario). Although these are primarily designed for application to drugs specific to particular proteins, they also can be adapted to design of drugs specific to regions of DNA or RNA, once that region is identified.

VI. Administration of Therapeutic Agents This disclosure contemplates IRX5 inhibitory agents, which are at least useful for treating hyperproliferative disorders, such as neoplasia. These agents include, for example, small inhibitory RNAs (siRNA), shRNAs, anti-sense nucleic acids, ribozymes, aptamers, mirror-image aptamers,

IRX5 dominant negative peptides, IRX5 inhibitory antibodies, small organic or inorganic molecules. Delivery systems and treatment regimens useful for such agents are known and can be used to aclrninister these agents as therapeutics. In addition, representative embodiments are described below. 1. Administration of Nucleic Acid Molecules In some embodiments where the therapeutic molecule is itself a nucleic acid (for example, siRNA, shRNA, ribozyme or anti-sense oligonucleotide) or where a nucleic acid encoding a therapeutic protein or peptide is contemplated, administration of the nucleic acid may be achieved by an appropriate nucleic acid expression vector which is administered so that it becomes intracellular, for example, by use of a retroviral vector (see U.S. Patent No. 4,980,286), or by direct injection, or by use of microparticle bombardment (for example, a gene gun; Biolistic, Dupont), or coating with lipids or cell-surface receptors or transfecting agents, or by administering it in linkage to a homeobox-like peptide which is known to enter the nucleus (see e.g., Joliot et al, Proc. Natl. Acad. Sci., 88:1864-8,1991). Alternatively, the nucleic acid can be introduced intracellularly and incorporated within host cell DNA for expression, for example, by homologous or non-homologous recombination. The vector pCDNA is an example of a method of introducing the foreign cDNA into a cell under the control of a strong viral promoter (CMV) to drive the expression. However, other vectors can be used. Other retroviral vectors (such as pRETRO-ON, Clontech) also use this promoter but have the advantages of entering cells without any transfection aid, integrating into the genome of target cells only when the target cell is dividing. It is also possible to turn on the expression of a therapeutic nucleic acid by administering tetracycline when these plasmids are used. Hence these plasmids can be allowed to transfect the cells, then administer a course of tetracycline to achieve regulated expression. Other plasmid vectors, such as pMAM-neo (also from Clontech) or pMSG (Pharmacia) use the MMTV-LTR promoter (which can be regulated with steroids) or the SV10 late promoter (pSVL, Pharmacia) or metallothionein-responsive promoter (pBPV, Pharmacia) and other viral vectors, including retroviruses. Examples of other viral vectors include adenovirus, AAV (adeno-associated virus), recombinant HSV, poxviruses (vaccinia) and recombinant lentivirus (such as HIV). All these vectors achieve the basic goal of delivering into the target cell the cDNA sequence and control elements needed for transcription. All forms of nucleic acid delivery are contemplated by this disclosure, including synthetic oligos, naked DNA, plasmid and viral, integrated into the genome or not. Retroviruses have been considered a preferred vector for gene therapy, with a high efficiency of infection and stable integration and expression (Orkin et al, Prog. Med. Genet. 7:130- 142, 1988). A nucleic acid therapeutic agent can be cloned into a retroviral vector and driven from either its endogenous promoter (where applicable) or from the retroviral LTR (long terminal repeat). Other viral transfection systems may also be utilized for this type of approach, including adenovirus, adeno-associated viras (AAV) (McLaughlin et al, J. Virol. 62:1963-1973, 1988), Vaccinia virus (Moss et al, Annu. Rev. Immunol. 5:305-324, 1987), Bovine Papilloma virus (Rasmussen et al, Methods Enzymol. 139:642-654, 1987) or members of the herpesvirus group such as Epstein-Barr virus (Margolskee et al, Mol. Cell Biol 8:2837-2847, 1988). In addition to delivery of a nucleic acid therapeutic sequence to cells using viral vectors, it is possible to use non-infectious methods of delivery. For instance, lipidic and liposome-mediated gene delivery has recently been used successfully for transfection with various genes (for reviews, see Templeton and Lasic, Mol. Biotechnol, 11:175 180, 1999; Lee and Huang, Crit. Rev. Ther. Drug Carrier Syst, 14:173-206, 1997; and Cooper, Semin. Oncol, 23:172-187, 1996). For instance, cationic liposomes have been analyzed for their ability to transfect monocytic leukemia cells, and shown to be a viable alternative to using viral vectors (de Lima et al, Mol. Membr. Biol, 16:103-109, 1999). Such cationic liposomes can also be targeted to specific cells through the inclusion of, for instance, monoclonal antibodies or other appropriate targeting ligands (Kao et al, Cancer Gene Ther., 3:250-256, 1996). Other representative methods of delivery of nucleic acids, including siRNAs and shRNAs-, are described in U.S. Pat. App. Pub. Nos. 20050008617, 20040204377, 20040162235, 20040106567, and 20030148519; and PCT Pub. Nos. WO 02/094185, WO 03/076592, WO 2004/048545, WO 2005/007854, WO 2004/029213, WO 2004/076674, and WO 2005/009476. 2. Administration of Polypeptides or Peptides In some embodiments, therapeutic agents comprising polypeptides or peptides may be delivered by administering to the subject a nucleic acid encoding the polypeptide or peptide, in which case the methods discussed in the section entitled "Administration of Nucleic Acid Molecules" should be consulted. In other embodiments, polypeptide or peptide therapeutic agents may be isolated from various sources and administered directly to the subject. For example, a polypeptide or peptide may be isolated from a naturally occurring source. Alternatively, a nucleic acid encoding the polypeptide or peptide may be expressed in vitro, such as in an E. coli expression system, as is well known in the art, and isolated in amounts useful for therapeutic compositions. 3. Methods of Administration, Formulations and Dosage Methods of administering an IRX5 inhibitory agent disclosed herein include, but are not limited to, intraprostatic, intrathecal, intradermal, intramuscular, intraperitoneal (ip), intravenous (iv), subcutaneous, intranasal, epidural, and oral routes. The therapeutics may be administered by any convenient route, including, for example, infusion or bolus injection, topical, absorption through epithelial or mucocutaneous linings (for example, oral mucosa, rectal and intestinal mucosa, and the like) ophthalmic, nasal, and transdermal, and may be administered together with other biologically active agents. Administration can be systemic or local. In addition, it may be desirable to introduce a pharmaceutical composition by any suitable route, including intraventricular and intrathecal injection; intraventricular injection may be facilitated by an intraventricular catheter, for example, attached to a reservoir. Pulmonary administration can also be employed (for example, by an inhaler or nebulizer), for instance using a formulation containing an aerosolizing agent. In specific embodiments, an IRX5-specific siRNA is injected directly into the vasculature of a subject, such as a human; for example, a siRNA can be injected intravenously. Methods for intravascular injection of siRNAs are known (see, for example, Lewis et al, Nat. Genetics, 32:107-108, 2002; McCaffrey et al, Nature, 418:38-39, 2002; Filleur et al, Cancer Res., 63:3919-3922, 2003). In some examples, self-assembling nanoparticles with siRNA can be administered intravenously (e.g., Schiffelers et al, Nucleic Acids Research, 32(19):el4, 2004). Such nanoparticles can be further constructed with polyethyleneimine (PEI) that is PEGylated with a tumor-specific peptide ligand attached at the distal end of the polyethylene glycol (PEG) as a means to target the siRNA nanoparticle to the tumor. In other embodiments, delivery of siRNA to cells (such as tumor cells) can be accomplished using lipophilic siRNAs conjugated with derivatives of cholesterol, lithocholic acid or lauric acid (e.g., Lorenz et al, Bioorganic & Medicinal Chemistry Letters, 14(19):4975-4977, 2004). In such instances, the lipid moieties can be covalently linked to the 5' ends of the RNAs, e.g., using phosphoramidite chemistry. Advantageously, lipophilic siRNAs can be administered with or without transfection agents. In a specific embodiment, it may be desirable to administer a pharmaceutical composition locally to the area in need of treatment. This may be achieved by, for example, and not by way of limitation, local or regional infusion or perfusion during surgery, topical application (for example, wound dressing), injection, catheter, suppository, or implant (for example, implants formed from porous, non-porous, or gelatinous materials, including membranes, such as sialastic membranes or fibers), and the like. In one embodiment, administration can be by direct injection at the site (or former site) of a tissue that is to be treated, such as the prostate. In another embodiment, the therapeutic are delivered in a vesicle, in particular liposomes (see, e.g., Langer, Science 249, 1527, 1990; Treat et al. , in Liposomes in the Therapy of Infectious Disease and Cancer, Lopez-Berestein and Fidler (eds.), Liss, N.Y., pp. 353-365, 1989). In yet another embodiment, the therapeutic agent can be delivered in a controlled release system. In one embodiment, a pump may be used (see, e.g., Langer Science 249, 1527, 1990; Sefton Crit Rev. Biomed. Eng. 14, 201, 1987; Buchwald et al, Surgery 88, 507, 1980; Saudek et al, N. Engl J. Med. 321, 574, 1989). In another embodiment, polymeric materials can be used (see, e.g., Ranger et al, Macromol Sci. Rev. Macromol Chem. 23, 61, 1983; Levy et al, Science 228, 190,

1985; During et al, Ann. Neurol 25, 351, 1989; Howard et al, J. Neurosurg. 71, 105, 1989). Other controlled release systems, such as those discussed in the review by Langer (Science 249, 1527 1990), can also be used. The vehicle in which the agent is delivered can include pharmaceutically acceptable compositions known to those with skill in the art. For instance, in some embodiments, therapeutic agents disclosed herein are contained in a pharmaceutically acceptable carrier. The term "pharmaceutically acceptable" means approved by a regulatory agency of the federal or a state government or listed in the U.S. Pharmacopoeia or other generally recognized pharmacopoeia for use in animals, and, more particularly, in humans. The term "carrier" refers to a diluent, adjuvant, excipient, or vehicle with which the therapeutic is administered. Such pharmaceutical carriers can be sterile liquids, such as water and oils, including those of petroleum, animal, vegetable, or synthetic origin, such as peanut oil, soybean oil, mineral oil, sesame oil, and the like. Water is a preferred carrier when the pharmaceutical composition is administered intravenously. Saline solutions, blood plasma medium, aqueous dextrose, and glycerol solutions can also be employed as liquid carriers, particularly for injectable solutions. The medium may also contain conventional pharmaceutical adjunct materials such as, for example, pharmaceutically acceptable salts to adjust the osmotic pressure, lipid carriers such as cyclodextrins, proteins such as serum albumin, hydrophilic agents such as methyl cellulose, detergents, buffers, preservatives and the like. Examples of pharmaceutical excipients include starch, glucose, lactose, sucrose, gelatin, malt, rice, flour, chalk, silica gel, sodium stearate, glycerol monostearate, talc, sodium chloride, dried skim milk, glycerol, propylene, glycol, water, ethanol, and the like. The therapeutic, if desired, can also contain minor amounts of wetting or emulsifying agents, or pH buffering agents. The therapeutic can take the form of solutions, suspensions, emulsion, tablets, pills, capsules, powders, sustained-release formulations, and the like. The therapeutic can be formulated as a suppository, with traditional binders and carriers such as triglycerides. Oral formulation can include standard carriers such as pharmaceutical grades of mannitol, lactose, starch, magnesium stearate, sodium saccharine, cellulose, magnesium carbonate, and the like. A more complete explanation of parenteral pharmaceutical carriers can be found in Remington: The Science and Practice of Pharmacy (19th Edition, 1995) in chapter 95. Embodiments of other pharmaceutical compositions are prepared with conventional pharmaceutically acceptable counterions, as would be known to those of skill in the art. Therapeutic preparations will contain a therapeutically effective amount of at least one active ingredient, preferably in purified form, together with a suitable amount of carrier so as to provide proper administration to the patient. The formulation should suit the mode of administration. Therapeutic agents of this disclosure can be formulated in accordance with routine procedures as a pharmaceutical composition adapted for intravenous administration to human beings. Typically, compositions for intravenous administration are solutions in sterile isotonic aqueous buffer. Where necessary, the composition may also include a solubilizing agent and a local anesthetic such as lignocaine to ease pain at the site of the injection. The ingredients in various embodiments are supplied either separately or mixed together in unit dosage form, for example, in solid, semi-solid and liquid dosage forms such as tablets, pills, powders, liquid solutions, or suspensions, or as a dry lyophilized powder or water free concentrate in a hermetically sealed container such as an ampoule or sachette indicating the quantity of active agent. Where the composition is to be administered by infusion, it can be dispensed with an infusion bottle containing sterile pharmaceutical grade water or saline. Where the composition is administered by injection, an ampoule of sterile water or saline can be provided so that the ingredients may be mixed prior to administration. The amount of the therapeutic that will be effective depends on the nature of the disorder or condition to be treated, as well as the stage of the disorder or condition. Effective amounts can be determined by standard clinical techniques. The precise dose to be employed in the formulation will also depend on the route of administration, and should be decided according to the judgment of the health care practitioner and each patient's circumstances. An example of such a dosage range is 0.001 to 200 mg/kg body weight in single or divided doses. Another example of a dosage range is 0.01 to 100 mg/kg body weight in single or divided doses. In some particular embodiments, an IRX5-specific siRNA is administered to a subject, such as a human, by intraperitoneal injection at a dosage of 0.01 to 0.150 mg/kg/day (see, for example, Filleur et al, Cancer Res., 63:3919-3922, 2003). The specific dose level and frequency of dosage for any particular subject may be varied and will depend upon a variety of factors, including the activity of the specific compound, the metabolic stability and length of action of that compound, the age, body weight, general health, sex, diet, mode and time of administration, rate of excretion, drag combination, and severity of the condition of the host undergoing therapy. The therapeutic agents of the present disclosure can be administered at about the same dose throughout a treatment period, in an escalating dose regimen, or in a loading-dose regime (for example, in which the loading dose is about two to five times the maintenance dose). In some embodiments, the dose is varied during the course of a treatment based on the condition of the subject being treated, the severity of the disease or condition, the apparent response to the therapy, and/or other factors as judged by one of ordinary skill in the art. In some embodiments long-term treatment with the drug is contemplated, for instance in order to reduce the occurrence of expression or overexpression of the target gene (such as, IRX5). In some embodiments, sustained rntra-prostatic (or near-prostatic) release of the pharmaceutical preparation that comprises a therapeutically effective amount of the particular therapeutic agent may be beneficial. Slow-release formulations are known to those of ordinary skill in the art.

VH. Combination Therapy The present disclosure also contemplates combinations of IRX5 inhibitory agent(s) with one or more other agents or therapies useful in the treatment of a disease, including, for example, hyperproliferative disease, such as a neoplasm. For example, IRX5 inhibitory agent(s), such as IRX5-specific siRNAs, may be administered in combination with effective doses of other medicinal and pharmaceutical agents (e.g., other anti-proliferative agents), or in combination with other therapies, such as hormone therapy (including, for example, orchiectomy) or radiation therapy. The term "administration in combination with" refers to both concurrent and sequential administration of the active agents. IRX5 inhibitory agents disclosed herein can be used in combination with other therapeutic agents, such as other anti-proliferative or anti-neoplastic agents. Examples of such agents are alkylating agents, antimetabolites, antimitotic agents, natural products, or hormones and their antagonists. Examples of alkylating agents include nitrogen mustards (such as mechlorethamine, cyclophosphamide, melphalan, uracil mustard or chlorambucil), alkyl sulfonates (such as busulfan), nitrosoureas (such as carmustine, lomustine, semustine, streptozocin, or dacarbazrne). Examples of antimetabolites include folic acid analogs (such as methotrexate), pyrimidine analogs (such as 5-FU or cytarabine), and purine analogs, such as mercaptopurine or thioguanine. Examples of antimitotic agents include microtubule-stabilizing agents (such as, paclitaxel and its analogues, docetaxel, abraxane, epothilones (such as epothilone A, B, D, and others), discodermolide, patupilone (EPO906), eleutherobins, laulimalide and its analogues (such as, C(16)-C(17)-des-epoxy laulimalide and C(20)-methoxy laulimalide), WS9885B, C-7 substituted eleutheside analogues (e.g., Castoldi et al, Tetrahedron, 61(8):2123-2139, 2005), ceratamine A, and ceratamine B) and microtubule-destabilizing agents (such as, vincristine, vinblastine, vinorelbine, and colchicine). Examples of natural products include vinca alkaloids (such as vinblastine, vincristine, or vindesine), epipodophyllotoxins (such as etoposide or teniposide), antibiotics (such as dactinomycin, daunorubicin, doxorubicin, bleomycin, plicamycin, or mitocycin C), and enzymes (such as L- asparaginase). Examples of miscellaneous agents include platinum coordination complexes (such as cis-diamine-dichlorόplatinum II also known as cisplatin), substituted ureas (such as hydroxyurea), methyl hydrazine derivatives (such as procarbazine), and adrenocrotical suppressants (such as mitotane and aminoglutethimide). Examples of hormones and antagonists include adrenocorticosteroids (such as prednisone), progestins (such as hydroxyprogesterone caproate, medroxyprogesterone acdtate, and magestrol acetate), estrogens (such as diethylstilbestrol and ethinyl estradiol), antiestrogens (such as tamoxifen), and androgens (such as testerone proprionate and fluoxymesterone). Examples of the most commonly used chemotherapy drags that could be used in combination with the IRX5 inhibitory agents include Adriamycin, Alkeran, Ara-C, BiCNU, Busulfan, CCNU, Carboplatinum, Cisplatinum, Cytoxan, Daunorubicin, DTIC, 5-FU, Fludarabine, Hydrea, Idarabicin, Ifosfamide, Methotrexate, Mithramycin, Mitomycrn, Mitoxantrone, Nitrogen Mustard, Taxol (or other taxanes, such as docetaxel), Velban, Vincristine, VP-16, while some more newer drags include Gemcitabine (Gemzar), Herceptin, Irinotecan (Camptosar, CPT-11), Leustatin, Navelbine, Rituxan STI-571, Taxotere, Topotecan (Hycamtin), Xeloda (Capecitabine), Zevelin and Vitamin D drugs (such as, calcitriol, Hectoral, DN-101, Rocaltrol® (Roche Laboratories), Calcijex® injectable calcitriol, investigational drags from Leo Pharmaceutical including EB 1089 (24a,26a,27a- teihomo-22,24-diene-lαa,25-(OH)₂-D₃), KH 1060 (20-epi-22-oxa-24a,26a,27a-trihomo-lα,25-(OH)₂- D₃), MC 1288 and MC 903 (calcipotriol), Roche Pharmaceutical drugs including l,25-(OH)₂-16-ene- D₃, l,25-(OH)₂-16-ene-23-yne-D₃, and 25-(OH)₂-16-ene-23-yne-D₃, Chugai Pharmaceuticals' 22- oxacalcitriol (22-oxa-lα,25-(OH)2-D₃; lα-(OH)D₅ from the University of Illinois; and drags from the Institute of Medical Chemistry-Schering AG that include ZK 161422 and ZK 157202). In certain embodiments involving administration of calcitriol, the calcitriol is administered in a therapeutically effective pulse dose no more than once every three days. Alternatively, the calcitriol is administered orally in a dose of at least 0.12 meg (μg)/kg per day no more than once per week. In yet another alternative, the calcitriol is administered orally in a dose of at least 0.48 mcg/kg or about 1 mcg/kg per day no more than once per week. Still other embodiments, involve administering about 180 meg (e.g., about 2.2 mcg/kg) calcitriol every 21 days or so. In addition, IRX5 inhibitory agents may be administered in combination with effective doses of radiation, immunomodulators, anti-inflammatories, anti-infectives, hypomethylation agents, nucleosides and analogs thereof, and/or vaccines. Non-limiting examples of immunomodulators that can be used in combination with an IRX5 inhibitory agent (such as a siRNA specific for IRX5) are AS-101 (Wyeth-Ayerst Labs.), bropirimine (Upjohn), gamma interferon (Genentech), GM-CSF (granulocyte macrophage colony stimulating factor; Genetics Institute), IL-2 (Cetus or Hoffman-LaRoche), human immune globulin (Cutter Biological), IMREG (from Imreg of New Orleans, La.), SK&F 106528, and TNF (tumor necrosis factor; Genentech). The combination therapies are of course not limited to the lists provided in these examples, but includes any composition for the treatment of diseases or conditions to which the IRX5 inhibitory agent is targeted.

The following examples are provided to illustrate certain particular features and/or embodiments. These examples should not be construed to limit the invention to the particular features or embodiments described.

EXAMPLES Example 1 IRX5 is Downregulated in Calcitriol-treated Patients This example demonstrates that IRX5 gene expression is downregulated in prostate tissue of human subjects treated with calcitriol (the active form of Vitamin D3, and also known as 1 ,25-dihydroxycholecalciferol). After election of surgical treatment for histologically confirmed adenocarcinoma of the prostate, patients were randomly assigned to receive either calcitriol (0.5 μg/kg) or placebo one time per week for 4 weeks prior to prostatectomy. Following completion of the assigned treatments, prostatectomy was performed on each subject and the removed prostate tissue was collected. Prostatic adenocarcinoma in the collected tissues was confirmed by histological examination. Gene expression analysis was carried out using RNA extracted from snap-frozen prostatectomy tissue collected from five calcitriol-treated patients and five placebo-treated patients (selected to ensure equal distribution of Gleason scores). Affymetrix human U133A DNA microarray chips were used in accordance with the manufacturer's instructions. Image processing, signal quantification and normalization were performed using Affymetrix Microarray Suite 5.0 software. The expression data from the ten microarrays were analyzed using the statistical tool

'Significance Analysis of Microarray' (SAM) (Stanford University) and a two-sample independent t- test was applied to each gene individually to compare treated and control samples. As shown in FIG. 1, cluster analysis based on the most significant 156 genes showed complete separation of calcitriol-treated and control (i.e., placebo-treated) tissues. Thus, this set of 156 genes could be used with 100% accuracy to predict which patients received calcitriol and which patients received placebo. Advantageously, this gene expression analysis identified calcitriol-regulated targets in a human prostate cancer model. This provides an important distinction from other prostate gene expression studies, which use pre-clinical models, such as prostate cancer cell lines, immunodeficient mice implanted with prostate cancer cells, non-immune deficient mice or rats implanted with mouse or rat prostate cancer cell lines, mice or rats that develop prostate cancer spontaneously or otherwise, or beagle dogs. Such laboratory models can only partially represent human disease. DNA microarray chip results showed that Iroquois homeobox protein 5 (IRX5), a homeobox gene, was significantly downregulated in calcitriol-treated tumors relative to controls (raw p = 0.0000008). As shown in FIG. 2, the downregulation of IRX5 was verified by real time reverse transcriptase polymerase chain reaction (real-time RT PCR) using RNA from the same human specimens analyzed by DNA microarray chip. Real time RT PCR was performed by extracting total RNA from treated and untreated patient samples using an RNeasy™ kit (Qiagen). RNA was pre-treated with TURBO DNAse™ (Product No. 2238, Ambion) to eliminate any residual genomic DNA. cDNA was made from the RNA templates using Superscript II™ reverse transcriptase (Product No. 18064 014, Invitrogen) and random hexamers. Four hundred (400) ng cDNA and 18S rRNA MGB endogenous control primers/probe (Product No. 4319413E, Applied Biosystems) were combined with TaqMan Universal PCR Master Mix™ (Product No. 4304437, Applied Biosystems) and ran on an ABI PRISM 7000 Sequence Detection System using proprietary IRX5 primers and probes from Applied Biosystems (HS00373920_gl). RNA expression was quantified by the comparative delta-delta Ct method (as described in Applied Biosystem's User Bulletin#2). As shown in FIG. 2, IRX5 expression (normalized tol8S rRNA expression) was reduced 65% (p < 0.001 ; n = 3) in calcitriol-treated patients as compared to control subjects.

Example 2 IRX5 Downregulation in 1,25-Dihydroxyvitamin D3 (l,25(OH)₂D₃)-treated LNCaP Cells This example demonstrates that l,25(OH)₂D₃ treatment downregulates IRX5 in an in vitro cell model. The prostate cancer cell line, LNCaP, was incubated with 10 nM l,25(OH)₂D₃ for- 24, 48, 72, 96 and 120 hours. Cells were collected by centrifugation at the indicated time points and total RNA was isolated as described in Example 1. IRX5 expression in l,25(OH)₂D₃-treated and control LNCaP cell was determined using real-time RT PCR as described in Example 1. As shown in FIG. 3, a consistent and significant reduction in IRX5 was observed after

48 hours incubation with l,25(OH)₂D₃, and decreased IRX5 expression was maintained for up to 120 hours. These results demonstrate that a single l,25(OH)₂D₃ treatment can suppress IRX5 expression in LNCaP cells for at least 120 hours. Example 3 IRX5 Downregulated Inhibits LNCaP Cell Proliferation This example demonstrates that small inhibitory RNAs (siRNA) can be used to decrease IRX5 RNA expression. In addition, this example shows that decreasing IRX5 expression leads to a decrease in treated cell numbers. LNCaP cells were transfected with 200nM of three different IRX5 siRNAs (which target the nucleic acid sequences shown in SEQ ID NOs: 5, 8, or 11, respectively) or the control siRNA, Cy3- Luc GL2 (siGL2; which targets the nucleic acid sequence shown in SEQ ID NO: 14) using Oligofectamine™ Reagent (Product No. 12252-011, Invitrogen). IRX5 siRNA#l targets the open reading frame (ORF) of the IRX5 mRNA. IRX5 siRNA#2 targets the 3'UTR. IRX5 siRNA#3 targets the IRX5 ORF. All siRNA oligos were BLAST searched against the human genome and no identical sequences were found. All siRNAs were purchased from Dharmacon. LNCaP cells were counted 96 hours after transfection using a hemocytometer. Then, total RNA was isolated and Real-time RT PCR was performed, each as described in Example 1. As shown in FIGS. 4 and 6, LNCaP cell numbers were reduced 96 hours following transfection of LNCaP cells with each of IRX5 siRNA#l, IRX5 siRNA#2, and IRX5 siRNA#3 as compared to the number of siGL2-transfected LNCaP cells at the same time point. For example, transfection with IRX5 siRNA#2 (see, FIGS. 4 and 6) and IRX5 siRNA#3 (see, FIG. 6) resulted in at least a 50% decrease in LNCaP cell number at 96 hours post-transfection as compared to control (pθ.001). Real-time RT PCR analysis revealed that IRX5 expression was reduced by 86% at 24 hours and 40% at 96 hours after transfection of LNCaP cells with IRX5 siRNA#2. A time course of the effect of IRX5 siRNA#2 transfection on LNCaP cells (see FIG. 5) shows that the cell numbers are reduced approximately 60% compared to control siGL2 -transfected cells at 120 hours. Interestingly, a dose response curve of LNCaP cells incubated with 10 nM l,25(OH)₂D₃ (see

FIG. 7) shows that l,25(OH)₂D₃ incubation and IRX5 siRNA transfection have similar effects on LNCaP cell numbers at the same time point (96 hours). This result indicates that l,25(OH)₂D₃ effects on LNCaP cell number may be mediated, at least in part, by IRX5 expression. /. Co-administration ofl,25(OH)->Dι andIRX5 siRNA#3 To further examine the relationship between l,25(OH)₂D₃ administration and suppression of

IRX5 expression, 100,000 LNCaP cells were plated in 6- well plates and transfected 48 hours later with 200 nmol siGL2 or IRX5 siRNA#2 using Oligofectamine (Invitrogen) according to the manufacture's recommendations. The transfected cells were grown in the presence or absence of 10 nM l,25(OH)₂D₃ for 96 hours. Cells were then harvested by trypsinization and counted using a hemocytometer to determine cell number. As shown in FIG. 14, l,25(OH)₂D₃ administration reduced the number of control-transfected (i.e., siGL2-transfected) LNCaP cells (compare G+V-/2- to G+V+/2- in FIG. 14). Consistent with above-reported observations, IRX5 siRNA#2-transfected cells were similarly reduced in number as were the l,25(OH)₂D₃-treated cells (compare G-V-/2+ to G+V+/2- in FIG. 14). Interestingly, co-administration of l,25(OH)₂D₃ with the IRX5 inhibitor, IRX5 siRNA#2, resulted in a further suppression of LNCaP cell growth as compared the results obtained with either agent alone. These results demonstrate that co-administration of l,25(OH)₂D₃ with an IRX5 inhibitory agent provides an enhanced cell growth inhibitory effect.

Example 4 Downregulation of IRX5 by RNA Interference Induces Apoptosis in LNCaP Cells This example demonstrates that inhibition of IRX5 induces apoptosis in LNCaP cells. Hoechst 33258 staining and Western blot analysis were each used to determine if apoptosis is induced by IRX5 downregulation. FIG. 8 shows the percentage of LNCaP cells undergoing apoptosis in response to transfection with 200nM IRX5 siRNA#2, as measured by Hoechst 33258 staining (as described in Garzotto et al, Cancer Res., 58:2260-2264, 1998). Four hundred cells IRX5 siRNA#2- and 400 GL2 contiol-transfected cell populations were counted under a fluorescent microscope at each time point shown in FIG. 8. Cells were counted as apoptotic if they displayed at least three apoptotic bodies. FIG. 9 shows the difference in morphology between non-apoptotic control cells and apoptotic IRX5 siRNA#2-transfected cells. No apoptotic bodies were visible in transfected contiol cells. In contrast, several apoptotic bodies were identified in IRX5 siRNA#2 -transfected cells. Western blot analysis using an antibody to the p85 kD fragment of PARP (Product No. G7341, Promega, WI) was next performed. This antibody binds only the p85kD PARP fragment and does not identify uncleaved PARP. The 85 kD PARP fragment results from caspase cleavage, and the detection of PARP cleavage by caspases has been established as a hallmark of apoptosis (see, for example, Duriez and Shah, Biochem. Cell. Biol, 75:337-349, 1997; Simbulan-Rosenthal et al, J. Biol. Chem., 273:13703-13712, 1998). LNCaP cells were transfected with GL2 siRNA (contiol), IRX5 siRNA#2 or IRX5 siRNA#3 as described above. Ninety-six hours after transfection, all transfected cells (both adherent and non-adherent) were harvested (as needed by trypsinization) and lysed in RIPA buffer as described in Santa Cruz Biotechnology Research Applications (Santa Cruz, CA). Forty-eight μg total protein was loaded into each well of a 10%) denaturing polyacrylamide gel. β-Tubulin (Product No. T5293, Sigma) was used as -a loading control. Following electrophoresis, the proteins were transferred to a Hybond-P membrane (Amersham), blocked in 5% dry milk, and probed with the anti-PARP_p85 o antibody (dilution 1 :300). Blots were washed and incubated with secondary antibody and visualized by ECL (Amersham). FIG. 10 shows the presence of a PARP cleavage product in IRX5 siRNA#2- and IRX5 siRNA#3-transfected cell lysates. In comparison, no PARP cleavage product was observed in control (GL2-transfected) cell lysates. These results further indicate that IRX5 siRNAs lead to downregulation of IRX5 and apoptosis in target cells. FIG. 11A shows a time course of PARP cleavage following the transfection of LNCaP cells with GL2 siRNA (control) or IRX5 siRNA#3. Protein isolation and separation and Western blot analysis were performed as previously described except that 38 μg of total protein was loaded in each lane of the polyacrylamide gel. A PARP cleavage fragment is clearly evident in IRX5 siRNA#3 -transfected LNCaP cell lysates 72 and 96 hours after transfection. Similarly, a time course of PARP cleavage following the transfection of LNCaP cells with IRX5 siRNA#2 demonstrated PARP cleavage at 72 and 96 hours in IRX5 siRNA#2-transfected cells (see FIG. 1 IB). These results show that the siRNA#2- and siRNA#3-treated cells were undergoing apoptosis at those time points.

Example 5 IRX5 Downregulation Induces More Robust Apoptosis than Calcitriol Treatment This example demonstrates that direct inhibition of IRX5 expression using IRX5 siRNAs provides a more robust apoptotic response than does treatment with lOnM-lOOnM calcitriol (l,25(OH)₂D₃). This result indicates that direct inhibition of IRX5 expression (for example, using siRNAs) more efficiently reduces neoplastic cell growth than does calcitriol treatment because the maximum calcitriol concentration achieved to date in humans, even with pulse dosing (see, for example, U.S. Pat. No. 6,521,608), is about 2-15 nM. A PARP-cleavage time course was determined for l,25(OH)₂D₃-tieated LNCaP cells (lOnM) using the methods described in Example 4. FIG. 12 shows that a PARP-cleavage product is present in l,25(OH)₂D₃-treated cell lysates 24-96 hours after onset of treatment. However, 120 hours after beginning l,25(OH)₂D₃ treatment, no PARP-cleavage product is observed. FIG. 12 also shows that amount of PARP-cleavage product present in LNCaP cell lysates 96 hours following IRX5 siRNA#2 and IRX5 siRNA#3 transfection is greater than that present in LNCaP cells 96 hours after onset of l,25(OH)₂D₃ treatment. Hoechst staining of l,25(OH)₂D₃-treated LNCaP cells confirms that l,25(OH)₂D₃ does not efficiently induce apoptosis in LNCaP cells. LNCaP cells were treated with 10 or lOOnM l,25(OH)₂D₃. At the time points indicated in FIG. 13, cells were harvested and stained with Hoechst 33258 (as described in Example 4). As shown in FIG. 13, a maximum of 6% of l,25(OH)₂D -treated cells underwent apoptosis after incubation with 100 nM l,25(OH)₂D₃ for 96 hours. Even fewer apoptotic cells were observed among cells treated with 10 nM l,25(OH)₂D₃ or at other time points for either concentration of l,25(OH)₂D₃. These results indicate that, 96 and 120 hours after treatment, more robust apoptosis is induced in IRX5 siRNA-transfected LNCaP cells as compared to calcitriol-treated cells, even at a calcitriol dose of 100 nM.

Example 6 Specific shRNA Expression Inhibits IRX5 Expression In Vitro Stable expression of an IRX5-specific shRNA in vitro or in vivo is one method for longer-term activation of the IRX5 RNAi pathway, which pathway acts to suppress IRX5 gene expression. This Example illustrates that transient expression of IRX5-specific shRNA inhibits expression of IRX5 in LNCaP cells. In this Example, 500,000 LNCaP cells were plated in media without antibiotics and transfected 24 hours later with Lipofectamine 2000 and 4 μg of pENTR/Hl/To plasmid (Invitrogen,

K4920-00) containing either shGL2 (control) or IRX5 sh2 hairpin sequences (when expressed in vivo, the IRX5 sh2 sequence should yield siRNAs equivalent to IRX5 siRNA#2). The shGL2 and IRX5 sh2 oligonucleotides were: shGL2 top strand

5'-CAC CGC GTA CGC GGA ATA CTT CGA GAG ATC GAA GTA TTC CGC GTA CG-3'(SEQ

ID NO: 116); shGL2 bottom strand 5'-AAA ACG TAC GCG GAA TAC TTC GAT CTC TCG AAG TAT TCC GCG TAC GC-3 ' (SEQ

ID NO: 115);

IRX5 sh2 top strand

5'-CAC CAG AGA GAG ACA GAG AGA GAA CGA ATT CTC TCT CTG TCT CTC TC-3' (SEQ

ID NO: 110) IRX5 sh2 bottom strand

5'-AAA AGA GAGAGA CAG AGA GAGAAT TCGTTC TCT CTC TGT CTC TCT CT-3' (SEQ

ID NO: 109) Ninety-six (96) hours after transfection, the cells were harvested by trypsinization and counted with a hemocytometer. As shown in FIG. 15, expression of IRX5-specifϊc shRNA reduced the growth of transfected LNCaP cells by an average of about 55% as compared to control-transfected cells. When taken together with prior examples, this Example shows that shRNA and siRNA transfection produce similar levels of LNCaP growth inhibition in vitro. Accordingly, it is expected that IRX5-specific shRNAs can be stably expressed in vitro or in vivo and such stable expression of an IRX5 inhibitor reduces IRX5 expression and inhibits cell growth at least to the same extent observed with transient transfection of such shRNAs.

Example 7 Stable Expression of Doxycycline-Inducible IRX5 shRNA in LNCaP Cells This Example illustrates long-term and stable downregulation of IRX5 in LNCaP cells in vitro using an inducible siRNA system based on the tetracycline operator/repressor interaction. To briefly describe the expression system, a cell line that expresses the Tet repressor (TetR) is used as a host. The TetR host is transfected with an expression construct containing the operator region of the tetracycline (Tet) operon cloned between a promoter and an shRNA-encoding nucleic acid of interest (such as, an IRX5 shRNA). Binding of TetR to the Tet operator prevents transcription of the shRNA. However, transcription can be induced upon addition of the tetracycline derivative, doxycycline, which binds to TetR, changes its conformation, and prevents it from binding to the Tet operator region. To create a TetR-expressing LNCaP host cell line, LNCaP cells grown in T75 tissue culture flasks to 50% confluence were transfected with pcDNA6/TR (Invitrogen), a TetR expression vector, according to the manufacturer's recommendations. Stable TetR LNCaP tiansformants were selected using Blasticidin also in accordance with the manufacturer's recommendations. A pool of Blasticidin-resistant LNCaP clones was screened by Western blot analysis using an anti-TetR antibody (MoBiTec, Gδttingen, Germany) to verify TetR expression in the pooled clones. IRX5 sh2 or shGL2 ds-oligonucleotides (described above) were cloned into BLOCK-iT Inducible HI RNAi Entry Vector (#K4920-00, Invitrogen) in conformance with the manufacture's protocol. The BLOCK-iT Inducible HI RNAi Entry Vector has a cloning site for a double-stranded DNA encoding an shRNA of interest immediately downstream of the HI/TO pol III promoter. The HI /TO pol III promoter contains two Tet0₂ sites for tetracycline- or doxycycline-regulated expression of the shRNA. Cellular transcription of the dsDNA produces an shRNA that is processed into short interfering RNA (siRNA) capable of inhibiting expression of the target gene. In addition, BLOCK-iT Inducible HI RNAi Entry Vector contains a Zeocin™-resistance protein expression cassette for selection in eukaryotic host cells. TetR LNCaP cells were plated in T75 Falcon tissue culture flasks and grown to 50% confluence prior to Lipofectamine 2000 (Invitrogen) transfection with the IRX5 sh2 or shGL2 BLOCK-iT vectors (as specified by the manufacturer). Stable transformants were selected using 3 μg/ml Blasticidin (to stably maintain pcDNA6/TR expression) and 500 μg/ml Zeocin™ (to stably maintain IRX5 shRNA BLOCK-iT vector). Blasticidin- and Zeocin™-resistant clones were expanded in the absence of doxycycline for several weeks. Then, 1 μg/ml doxycycline (or other doxycycline concentration where cell toxicity is low and TetR is substantially inactive) is added to induce IRX5 shRNA expression in the stable transfectants. Similar to cells transiently transfected with IRX5-specific siRNAs (see, e.g., Example 3), a significant decrease is expected in the number of doxycycline-treated IRX5 shRNA stable transformants as compared to non-treated IRX5 shRNA stable transformants, or doxycycline-treated or -untreated shGL2 stable tiansformants. In addition, a significant increase in apoptosis is expected in doxycycline-treated IRX5 shRNA stable transformants as compared to controls. It is further anticipated that the growth inhibitory and apoptotic effects observable in the IRX5 shRNA stable transformants will be even more pronounced than with IRX5 siRNA transient transfections because of the stable integration of the IRX5 inhibitor (IRX5 sh2) into the LNCaP genome.

Example 8 IRX5 Overexpression Induces LNCaP Proliferation and Inhibits l,25(OH)₂D₃-induced Growth Suppression This Example demonstrates that IRX5 overexpression has a proliferative effect on LNCaP cells. In addition, IRX5 overexpression inhibits l,25(OH)₂D₃-induced apoptosis. These results support the view that IRX5 expression is growth stimulatory and that inhibition of IRX5 expression (such as, by IRX5-specific siRNAs or shRNAs) will inhibit cell growth (as shown in other Examples herein). The IRX5 coding region was cloned into pcDNA3 (Invitrogen) to produce a constitutively active IRX5 expression vector (pcDNA3-IRX5). Approximately 100,000 LNCaP cells per 6-well plate were plated in RPMI (Gibco) 10% FBS (Gibco) with no antibiotics. For each well, 2.5 μg pcDNA3-IRX5 or pcDNA3 (negative control) DNA was mixed with 100 μl OPTI-MEM media and, in a separate tube, 25 μL Lipofectin (Invitrogen) was mixed with 100 μl OPTI-MEM media. These mixtures were incubated for 45 minutes. After incubation, the Lipofectin and DNA were mixed and allowed to incubate for 15 minutes prior to addition to each well. Trials were performed in sets of six. After 4 hours, calcitriol was added to appropriate wells at a final concentration of 100 μM.

Then, cells were grown for 96 hours, harvested by trypsinization and counted with a hemacytometer. As shown in FIG. 16, IRX5 stimulated LNCaP cell growth as compared to contiol (compare -VD/+I5 to -VD/-I5 in FIG. 16). In comparison, cell growth was inhibited in the presence of l,25(OH)₂D₃ (see +VD/-I5 in FIG. 16). As previously described, l,25(OH)₂D₃ administration induces apoptosis in LNCaP cells, which would account, at least in part, for the observed decrease in l,25(OH)₂D₃-treated cell number in this Example. Interestingly, IRX5 overexpression in the presence of l,25(OH)₂D₃ was able to overcome l,25(OH)₂D₃-induced growth suppression in LNCaP cells (compare +VD/+I5 to +VD/-I5 in FIG. 16). Example 9 IRX5 Overexpression Downregulates p21 This Example shows that IRX5 overexpression downregulates p21, an important molecule involved in cell-cycle arrest. T25s cells were transfected with pcDNA3-IRX5 or pcDNA3 as described in Example 8. Cells were treated with 100 nM calcitriol at the time of transfection. Six (6), 12 or 24 hours after transfection, media was removed and cells were lysed with RIPA buffer and the manufacturer's recommended amount of Complete Mini, EDTA-free protease inhibitor cocktail (Roche). Cells were scraped to remove from flask and allowed to sit on ice in an eppendorf tube for 1 hour. The cell extract was then centrifuged for 20 minutes at 13,000xg and supernatant was aliquoted and flash frozen. Total protein concentration in cell extracts was assayed by UV-Vis spectrophotometer using the Quick-start Bradford Dye Reagent (Bio-Rad) according to the supplier's instructions. Approximately 25 μg of protein was run per lane on NuPAGE 10%> Bis-Tris gel and standard NuPAGE MOPS buffer (Invitrogen). Separated proteins were transferred from the gel, using recommended transfer buffer, to H-bond membrane (Amersham Biosciences) overnight at 4°C at 30V. The membrane was washed three times with PBS/Tween (0.1%) (PBST) for 5 minutes each wash. The membrane was blocked with 5%> nonfat milk in PBST for 1 hour. The membrane was again washed in PBST for 5 minutes, then probed with p21 mouse monoclonal antibody (Santa Cruz sc-6246). The membrane was again washed with PBST and then reprobed with secondary bovine anti-mouse antibody (Santa Cruz sc-2371). The membrane was again washed three times for

10 minutes each, and then exposed to Western Lighting reagents (Perkin Elmer Life Sciences). Film was exposed to the membrane for 2 minutes, then developed. As shown in FIG. 17, p21 was downregulated by IRX5 overexpression, with peak decrease at 12 hours following tiansfection with pcDNA3-IRX5. Given that p21 is an extremely important molecule in cell-cycle arrest, this Example demonstrates that IRX5 expression affects the cell cycle.

Example 10 Isolation and Characterization of IRX5 Regulatory Region Using PCR, IRX5 promoter fragments of approximately 3000, 1500, 1250, 1000, 700, or

400 base pairs were amplified from LNCaP genomic DNA upstream of exon 1 of the IRX5 gene. The primer pairs used were: For 3000 base pair region: CTCGAGAGTTCTTTTAATTGTGATGTTAGAATGT (SEQ ID NO: 139) AAGCTTGTTGCAAATATTGCTAGGCTACTG (SEQ ID NO: 140) For 1500 base pair region:

CCCGGTACCGGGCATTATTGACTCTCAGTAAAAGC (SEQ ID NO: 141) CCCCTCGAGGTTGCAAATATTGCTAGGCTACTGG (SEQ ID NO: 142) For 1250 base pair region: CCCCTCGAGTAGAGTCAGAGTTCAGGACCACTC (SEQ ID NO: 143) CCCAAGCTTGTTGCAAATATTGCTAGGCTACTGG (SEQ ID NO: 144) For 1000 base pair region:

CCCCTCGAGAAATATTTGCAAGATCAGTGTTACAA (SEQ ID NO: 145) CCCAAGCTTGTTGCAAATATTGCTAGGCTACTGG (SEQ ID NO: 146) For 700 base pair region:

CCCGGTACCGGATGAATACTGCAGCTAGTAAAGTTTAC (SEQ ID NO: 147) CCCCTCGAGGTTGCAAATATTGCTAGGCTACTG (SEQ ID NO: 148) For 400 base pair region: CCCCTCGAGTATGTCAACAGCTTTTAAACTTAGATTT (SEQ ID NO: 149) CCCAAGCTTGTTGCAAATATTGCTAGGCTACTGG (SEQ ID NO: 150) The PCR was conducted using the Advantage-GC 2 PCR Kit with 0.5M GC-Melt (BD Biosciences), and a 56°C annealing temperature for 25 cycles. The PCR product was gel purified using the QIAquick Kit (Qiagen) and cut with Xhol and Hindlll (New England Biolabs). The digest was then gel purified again. The product was ligated into pGL3-Basic Luciferase reporter vector (Promega) using T4 DNA Ligase (New England Biolabs) at 15°C overnight. The ligation product was transformed into DH5α Cells (Invitrogen) and grown in LB-AMP overnight. Minipreps were performed using the QIAprep spin column mini prep system (Qiagen). A diagnostic digestion was performed and run on a gel, using the same procedure described above. Approximately

300,000 LNCaP cells were plated per well, allowed to recover for 36 hours and then transfected (as described above) with the pGL3-luciferase reporter vector containing the 1500 base pair regulatory region or the pGL3-luciferase reporter vector alone. After an additional 24 hours, transfected cells were lysed with 120 μl lysis buffer as described in the Luciferase Assay system (Promega). Forty (40) μl of the cell lysate was then transferred to a tube for the Luciferase assay, and 30 μl of the same mixture was transferred to a tube for the β-gal reading. Luciferase assay was performed according to specifications in the Luciferase Assay System (Promega) and β-gal assay was performed according to the luminescent β-gal detection kit II (BD Biosciences). Readings were recorded using a single- injector, multi-tube luminometer by ranning each reaction separately. As shown in FIG. 18, the control luciferase vector (pGL3) has a low transcriptional activity that is not affected by l,25(OH)₂D₃ (compare pGL3 +/- VD). Addition of the 1500-base pair IRX5 regulatory fragment to the pGL3 vector leads to increased expression of the luciferase reporter gene (see pGL3-1500 bp -VD in FIG. 18). This increased expression suggests that the 1500 bp IRX5 regulatory region includes regulatory elements that overall enhance transcription under the tested conditions. The IRX5-regulated luciferase expression is downregulated by 100 nM vitamin D (compare pGL3-1500 bp +/- VD), which further demonstrates the regulatory activity of the 1500 bp IRX5 upstream fragment. This and the other IRX5 regulatory region reporter constructs described in this Example can serve as useful reporting mechanisms for IRX5 expression.

Example 11 Stable Expression of IRX5 shRNA in LNCaP Cells Orthotopically Implanted into Mice Approximately 2 x 10⁶ IRX5 shRNA-expressing LNCaP cells (for example, as described in Example 7) in 50 μl are orthotopically implanted into mice and stable downregulation of IRX5 in the implanted LNCaP cells (following doxycycline induction of IRX5 shRNA expression) is determined by serial testing of mouse prostate tissue with real time RT-PCR and immunohistochemistry over a 21 -day period. The doxycycline-inducible IRX5 shRNA expression vector described, for example, in Example 7, is used, at least, because there is ample evidence that doxycycline-inducible gene expression works well in mice (Lottmann et al, J. Mol. Med., 79(5-6):321-8, 2001; Hutchinson and Muller, Oncogene, 19(53):6130-7, 2000; Kistner et al, Proc. Natl. Acad. Sci. USA, 93(20): 10933-8, 1996; Moody et al, Cancer Cell, 2(6):451-61, 2002; Schiffer et al, Cancer Res., 63(21):7221-31, 2003; Eger et al, Biochem. Biophys. Res. Commun., 323(3):979-86, 2004; Gossen and Bujard, Proc. Natl. Acad. Sci. USA, 89(12):5547-51, 1992; Czauderna et al, Nucleic Acids Res., 31(21):el27, 2003). Thus, this vector is expected to perform well in vivo. Orthotopic implantation of cells into mouse prostates has been previously described (Garzotto et al, Cancer Res., 59(20):5194-5201, 1999; Garzotto et al, Prostate, 33(l):60-63, 1997). Briefly, a transverse incision is made in the lower abdomen of immunodeficient BALB/c nude mice (Jackson Labs), and the bladder and seminal vesicles delivered through the incision to expose the dorsal prostate. LNCaP cells are injected under the prostatic capsule using a 30-gauge needle. The incision is closed by running suture. Beginning approximately 2 days after tumor cell implantation, doxycycline hydrochloride (100 μg/ml, Sigma) is administered to the mice via the drinking supply with 3% sucrose. The drinking supply is changed three times per week. Mouse prostates are harvested 48 hours, 96 hours, 1 week, 2 weeks, and 3 weeks after initiation of doxycycline administration. Harvested prostate tissues are bisected and one half is fixed and processed for immunohistochemistry, and the other half is flash frozen for RNA exfraction and real time RT-PCR. For immunohistochemical assays, formalin-fixed and paraffin-embedded prostate tumors are sectioned (5 μm), deparaffinized using a Leica autostainer, blocked in BSA and incubated with an IRX5-specific primary antibody at 4°C overnight. Following washing, a biotinylated secondary antibody is added and tissues incubated for 30 minutes at room temperature. Tissues are treated with hydrogen peroxide to quench endogenous peroxidase, rinsed, and incubated with the avidin-biotin peroxidase complex (ABC) Vectastain Elite (Vector Laboratories, Burlingame, CA), and the chromogen diaminobenzidine (DAB), and finally counterstained with hematoxylin and eosin (H&E) on a Leica autostainer. For real time RT-PCR, RNA from flash- frozen mouse prostate tissue is extracted using

TRIZOL reagent according to the manufacturer's instructions (Gibco BRL). Approximately 400 ng cDNA and 18S rRNA MGB endogenous control primers/probe (#4319413E, Applied Biosystems) are combined with TaqMan Universal PCR Master Mix (#4304437, Applied Biosystems) and run on an ABI PRISM 7000 Sequence Detection System using IRX5 primers and probes from Applied Biosystems (HS00373920_gl). All reactions are performed in triplicate. Details of this method have been previously described by Iwao et al. (Cancer, 89(8): 1732-1738, 2000). RNA expression is quantified by the comparative delta-delta Ct method (Applied Biosystem's User Bulletin #2). It is expected that doxycycline treatment of the mice will induce shIRX5 expression in the implanted LNCaP tumor and that long-term downregulation of IRX5 RNA will be observed with real time RT-PCR of RNA extracted from these tumors at the described time points.

Immunohistochemistry using an IRX5-specific antibody is expected to show a decrease in IRX5 expression in shIRX5-expressing tumors. Weighing the harvested tumors is expected to show that tumors in the doxycycline-treated, shIRX5-expressing group are significantly smaller than the tumors in the control group.

Example 12 Other Methods for Inhibiting IRX5 In Vivo This Example describes methods in addition to those described in Example 11 that can be used to inhibit IRX5 expression in vivo. tTA/LNCaP cells, which stably express the tetracycline-controlled transactivator tTA

(encoded by the pTet-Off regulator plasmid from Clontech) are stably transformed with a tetracycline-inducible vector expressing IRX5 antisense. The coding region of IRX5 is cloned (e.g., residues 1-1449 of SEQ ID NO: 1 or residues 1-1452 of SEQ ID NO: 3), in reverse orientation, into a docycycline-responsive pTRE vector (Clontech) to produce pTRE.ASIrx5. LNCaP cells stably expressing both tTA and pTRE.ASIrx5 are implanted into the prostates of nude mice as described in Example 11, and IRX5 antisense expression is induced by removal of doxycycline (100 μg/ml provided in the drinking water). Doxycycline-responsive expression of antisense has been successful in repressing the expression of a number of genes both in vitro and in vivo as described by Lottmann et al. (J. Mol. Med., 79(5-6):321-8, 2001), Hommura et al. (Mol. Cancer Res., 2(5):305-14, 2004), Dandekar and Lokeshwar (Clin. Cancer Res., 10(23):8037-47, 2004), and Coluccia et al. (Blood, 103(7):2787-94, 2004). In yet another approach, LNCaP cells are transiently transfected with IRX5 siRNA (e.g., IRX5 siRNA#2) and immediately implanted orthotopically into nude mice. Cells transiently transfected with an siRNA expression vector have been shown have a significant reduction in tumor size even after a month or more; in particular, Yoshinouchi et al. (Mol. Ther., 8(5):762-8, 2003) reported that HPV16-positive cervical cancer cells, which were transfected with E6 siRNA (21 nucleotides), showed a significant reduction in tumor size even after 45 days. Still another approach involves orthotopically implanting wild type LNCaP cells into mouse prostates with subsequent exogenous administration of IRX5 siRNA. This approach has been successfully used to target inhibition of a transcript in a tumor (see, e.g., McCaffrey et al, Nature, 418(6893):38-39, 2002; Lewis et al, Nat Genet, 32(1):107-108, 2002; Filleur et al, Cancer Res., 63(14):3919-3922, 2003). Each of the methods described in this Example provides additional means by which to inhibit IRX5 expression in vivo.

Example 13 IRX5-Specific shRNA Expression Inhibits Tumor Growth In Vivo Based on the discoveries disclosed herein, downregulation of IRX5 in a living subject is expected to inhibit tumor take and/or tumor growth, increase the apoptotic index and reduce tumor angiogenesis. As shown in Examples 4 and 5, downregulation of IRX5 was sufficient to induce substantial apoptosis in prostate cancer cells, even though prostate cancers are thought to be relatively resistant to apoptosis (Meyn, Oncology (Huntingt), l l(3):349-356, 1997). This Example describes the effect of IRX5 inhibition on a prostate cancer model wherein cancer cells induce angiogenesis, invade, and interact with prostate stroma, which is similar to the human disease process. Sixty-two (62) BALB/c nude mice are housed in accordance with NIH guidelines. Two million (2 x 10⁶) LNCaP cells stably transfected with a doxycycline-inducible IRX5 shRNA vector (see, e.g., Example 11) (in 50 μl) are surgically implanted in the orthotopic position of anesthetized (1.5% isoflurane) mice as previously described (Example 11; see, also, Garzotto et al, Prostate, 33(l):60-63, 1997; Garzotto et al, Cancer Res., 59(20):5194-201, 1999; Dai et al, Clin. Cancer Res., 7(5): 1370-1377, 2001). As described in Example 11, doxycycline hydrochloride is administered to a subset of 31 of the surgically implanted mice via the drinking supply. Tumor take and growth is monitored every 10 days by serum PSA testing and compared between mice that receive doxycycline (31 mice) and consequently express the IRX5 siRNA, and those that do not (31 mice). PSA is a 34 kD glycoprotein that is secreted by LNCaP cells into the serum of tumor-bearing mice. Any measurable amount of PSA indicates the presence of a prostate tumor. PSA levels strongly correlate to tumor volume (r = 0.95) (Garzotto et al, Cancer Res., 59(20):5194-5201, 1999; Gleave et al, Cancer Res., 52(6):1598-605, 1992). Phlebotomy (50 μl) of the retro-orbital plexus is carried out on isoflurane (1.5%)-anesthetized mice and PSA levels are determined using a commercially available radiormmunoassay kit (Hybritech) as previously described (Garzotto et al, Cancer Res., 59(20):5194-5201, 1999; Lim et al, Prostate, 22(2): 109- 118, 1993). Time to the first detection of PSA is analyzed using the Kaplan-Meier method (see, e.g.,

Kaplan and Meier, J. Am. Stat Assoc, 53:457-481, 1958) and compared between doxycycline-treated and control groups by the log-rank test. PSA kinetics are analyzed as the PSA doubling time (PSADT) calculated as LN(2)/regression coefficient of the PSA rise. The regression coefficient of the PSA rise and 95% confidence intervals are calculated using linear regression analysis with LN(PSA) as the dependent variable and time the independent variable using StatView 5.0 software (SAS Institute 1998). The tumor take using wild-type LNCaP cells in conjunction with the implantation procedure described in this Example has been shown previously to be approximately 70 to 80% (Stephenson et al, J. Natl. Cancer Inst, 84(12):951-957, 1992; Garzotto et al, Cancer Res., 58(10):2260-2264, 1998). Similar tumor-take percentages are expected for contiol mice in this Example, while doxycycline-treated mice are expected to have significantly lower tumor take. Fifty (50) days after onset of doxycycline administration, mice are sacrificed by 70% C0₂ inhalation in accordance with AVMA guidelines (AVMA Consensus Panel, 2000 Report of the AVMA Panel on Euthanasia, J. Am. Vet. Med. Assoc, 218:669, 2001). Prostate tissues are harvested, weighed, and bisected. Half of the prostate tissue is fixed in formalin and embedded in paraffin. The other half of the prostate tissue is snap frozen in liquid pentane for subsequent RNA extraction. Based on data reported by Stephenson etal. (J. Natl. Cancer Inst., 84(12):951-957, 1992), a mean + estimated SD for tumors in contiol mice is expected to be 250 + 100 mg. A total sample size of 43 permits detection of a 71 mg reduction (e.g., from about 250 mg (controls) to about 179 mg (treated)) in mean tumor weight with 90% power using a 2-sided t-test at 5% significance level.

Prostate tumor size is expected to be significantly less (e.g., up to 50% less) in doxycycline-treated mice as compared to control mice. To identify the presence of tumors, embedded prostate tissue is stained with hematoxylin and eosin (H&E), for instance, as described by Taboas and Ceremsak (Tech. Bull. Regist Med. Techno!., 37(4):119-120, 1967). In addition, immunohistochemistry of embedded sections is used to identify the in situ expression of CD31 (an endothelial cell marker), VEGF (a promoter of angiogenesis frequently overexpressed in prostate cancer), and selected apoptotic mediators. Antibodies for use in immunohistochemistry and other technologies involving antibodies (such as, western blots) include, anti Mdm2 antibody (07-575, Upstate Biotechnology, Lake Placid, NY), mouse monoclonal anti p21 antibody (sc-6246, Santa Cruz Biotechnology, CA), Gadd45α, γ, β (sc-6850, sc-8778, sc-8776, respectively, Santa Cruz Biotechnology, CA), rabbit polyclonal anti-Rb and anti-p-Rb (C-15 and sc-7986-R, respectively, Santa Cruz Biotechnology), rabbit polyclonal anti-Bcl-2 (N-19 Santa Cruz Biotechnology), rabbit polyclonal anti-Bax (N-20, Santa Cruz Biotechnology), anti-c-myc (N-262, Santa Cruz, CA), anti-p38 MAPK (sc-535, Santa Cruz; CA), anti-Akt (#9272, New England Biolabs), anti-phospho-Akt (#9271, New England Biolabs) (Akt is activated by phosphorylation), MEKKl (sc-252, Santa Cruz, CA) (to determine expression and caspase 3-mediated proteolytic cleavage), rabbit polyclonal anti-p53 (Santa Cruz, CA), anti-phosphop-53 Ser 15 (rabbit polyclonal, CELBIO, New England Biolabs, Beverly, MA), anti-ERKl/2 (06-182, Upstate Biotechnology), anti-phospho-ERKl/2 (sc-7383, Santa Cruz, CA), anti-TNFα (sc-1350, Santa Cruz, CA), rabbit polyclonal anti total JNK and monoclonal anti-phospho-JNK (Santa Cruz Biotechnology, CA), goat polyclonal anti-Smac/DIABLO (V-17, Santa Cruz), NF-kB/p65 and IkBα (Upstate Biotechnology, Lake Placid, NY), rabbit polyclonal anti-XIAP and anti-cIAP-1 (R&D Systems, MN), β-tubulin (Sigma, 1:1000), VEGF (sc-507, Santa Cruz, CA), CD31 (PECAM-1, Santa Cruz, CA). Angiogenesis is examined by microvessel density counts after immunohistochemistry for CD31 and VEGF. At least 400 cells are examined for VEGF expression which is quantified as a percentage of positively staining cells determined by a blinded examiner. Microvessel density is quantified as previously described by Zhou et al. (J. Nutr., 129(9):1628-1635, 1999) and Sato et al. (Cancer Res., 57(8):1584-1589, 1997). The microvessel density of prostate tumors in doxycycline-treated mice is expected to be less than that of control prostate tumors. Apoptosis in vivo is determined by the ApopTag Plus Peroxidase In Situ Apoptosis Detection Kit (#S7101, Intergen Company, NY) as directed by the manufacturer. Apoptotic cells are quantified by examining 500-1000 tumor cells from each tissue specimen at a magnification of 400x on a Leica microscope and counting the number of cells detected by the anti-digoxigenin antibody (included with the detection kit). The number of apoptotic cells are divided by the total number of cells counted to yield the apoptotic index (a minimum of 400). Based on published data (Zhou et al, Prostate, 53(2):143-153, 2002), the control group apoptotic index + SD is expected to be 3.2 + 0.5. In comparison, the doxycycline-treated group is expected to have a higher apoptotic index. A sample size of 21 prostate tumors per experimental group provides 90% power to detect an increase in the apoptotic index from 3.2%> to 4.0% using the student's t-test. If IRX5 downregulation profoundly inhibits tumor take and growth, there will not be sufficient tumor tissue with which to assess apoptosis and angiogenesis. This result would mean that not only can IRX5 downregulation treat (and/or reduce the growth of) neoplastic cells, but IRX5 downregulation can effectively eliminate tumor growth. If desired, implanted LNCaP cells containing a doxycycline-inducible IRX5 shRNA expression vector are allowed to become established tumors in test animals before inducing siRNA expression with doxycycline. The fate of the established tumors is then examined for apoptosis and angiogenesis shortly after the addition of doxycycline (e.g., 72 hours, 96 hours, and 120 hours), when induction of apoptosis would be expected based on in vitro data. Apoptosis detected in prostate tissue harvested from doxycycline-treated animals is expected to be higher than that measured in control animals. RNA isolated from snap-frozen prostate tissues and real time RT-PCR are used to confirm IRX5 downregulation in such tissues. An exemplary real time RT-PCR method is described in Example 11. IRX5 expression in doxycycline-treated animals is expected to be less than control animals. Tumor PSA expression is verified using western blot. Western blot is a standard technique in the art. Briefly, equal amounts of protein are resolved on 10-12% acrylamide gels and proteins are transferred to Hybond-P membranes (Amersham), blocked in 5% dry milk and 0.05% Tween-20, and probed with primary antibody for 1 hour at room temperature. Blots are washed and incubated with secondary antibodies (anti-rabbit or anti-mouse as appropriate to recognize the primary antibody) labeled with horseradish peroxidase (or other detector reagent) and visualized by ECL (Amersham). β-tubulin or actin protein samples of a known concentration are used as gel loading control. Consistent with radioimmunoassay results (described above), PSA expression in prostate tissue of doxycycline-treated animals (which express IRX5 shRNA in implanted LNCaP cells) is expected to be less than values from doxycycline-free animals.

Example 14 Inhibition of IRX5 Expression In Vivo by RNA Interference RNA interference can be mediated, for example, by small temporal RNAs (stRNAs) that are transcribed as short hairpin precursors of approximately 70 nucleotides (Paddison et al, Genes Dev., 16(8):948-958, 2002). Such structures have been shown in mammals to mediate repression of endogenous mRNAs that are complementary to the sequence of the stRNAs (Paddison et al, Genes Dev., 16(8): 48-958, 2002). Therefore, IRX5 expression in vivo may be inhibited by expressing inverted repeats of different portions of the IRX5 cDNA to form stable hairpin structures. An adenovirus vector (which infects non-dividing cells) expressing different inverted repeats of the IRX5 cDNA to form stable hairpin structures is constructed. For example, 140-base oligonucleotides containing 70-base inverted repeats of the IRX5 RNA sequence, or 70-base pair oligonucleotides containing 35-base inverted repeats of the IRX5 RNA sequence are produced or other similar constructs may be produced. Representative sequences of the IRX5, which are useful to construct inverted repeats, include any about 25, about 30, about 40, about 50, about 70 or even more nucleic acid residues of an IRX5 nucleic acid sequence (for example, SEQ ID NO: 1 or 3). In some embodiments, the IRX5 nucleic acid residues used to construct inverted repeats are contiguous. For example, a synthetic mini-gene containing nucleic acid sequences encoding any one of the sequences set forth in SEQ ID NOs: 117-138 would be expected to form a stable hairpin structure when synthesized. Non-limiting representative paired oligonucleotides that encode shRNAs are provided in SEQ ID NOs: 109-116. Synthetic mini-genes are cloned into adenoviral vectors using standard molecular biological techniques. Adenoviral vectors are advantageous because they infect a broad array of tissue types, they can be used in mice, rats, primates, and humans, they do not result in a permanent infection as they cannot replicate, and they have been approved for use in humans as gene therapy vectors. Adenoviral vectors are commercially available (for example, from Invitrogen, Clontech, Stratagene, or Q-Biogene), and production of recombinant adenovirus is routine (see, for example, Current

Protocols in Human Genetics, ed. by Dracopoli et al, New York: John Wiley & Sons, 2003, Chapter 12, Vectors for Gene Therapy, Unit 12.4, Adenoviral Vectors). Control adenoviral vectors expressing a reporter gene, such as EGFP or LacZ (for example, pShuttle-lacZ; Clontech), are readily available for use in optimizing infection procedures. The control viruses would be genetically engineered and purified using routine methods. To assay infectivity in vitro, 3 x 10⁵ target cells (such as LNCaP) per well of a 6-well plate are plated and increasing amounts of virus capable of expressing a contiol reporter gene, such as EGFP, (MOI of 0-1000 using 5-fold dilutions of virus) are added. Infection is allowed to proceed for 1 hour with rocking, then the media is aspirated and the cells are washed. Twenty four (24) to 48 hours later the transfected cells are fixed and analyzed for expression of the reporter, such as EGFP, using appropriate techniques, such as FACS analysis for EGFP expression. Adenovirus can also be used for in vivo infection (see, for example, Current Protocols in Human Genetics, ed. by Dracopoli et al, New York: John Wiley & Sons, 2003, Chapter 12, Vectors for Gene Therapy, Unit 12.4, Adenoviral Vectors). To assay infectivity in vivo, increasing amounts of virus capable of expressing a control reporter gene (0-1 x 10⁷ plaque forming units (PFUs)) are injected into a test animal, such as a mouse. Injections sites can vary but for this example a direct injection of different amounts of control viras into neoplasms of anesthetized mice is preferable. Twelve (12) to 15 days later, the infected mice are euthanized and expression of the reporter gene, such as EGFP, is analyzed. Having established appropriate conditions for infection as described above, recombinant adenovirus carrying different IRX5 hairpin constructs are injected in vivo and IRX5 expression is analyzed as previously described. One measure of inhibition of IRX5 expression in vivo is a decrease in the size (or number of neoplastic cells) of a neoplasm within several weeks of treatment. While this disclosure has been described with an emphasis upon particular embodiments, it will be obvious to those of ordinary skill in the art that variations of the particular embodiments may be used and it is intended that the disclosure may be practiced otherwise than as specifically described herein. Accordingly, this disclosure includes all modifications encompassed within the spirit and scope of the disclosure as defined by the following claims:

Claims

1. A method for the treatment of a hyperproliferative disorder in a subject, comprising administering to a subject a therapeutically effective amount of an IRX5 inhibitor other than a Vitamin D drag thereby treating the hyperproliferative disorder in the subject.

2. The method of claim 1, wherein the IRX5 inhibitor comprises a small inhibitory RNA (siRNA), a small hairpin RNA (shRNA), an anti-sense nucleic acid, a ribozyme, an aptamer, a mirror-image aptamer, an IRX5 dominant negative peptide, an IRX5 inhibitory antibody, or a combination thereof.

3. The method of claim 2, wherein the IRX5 inhibitor comprises a siRNA or a shRNA.

4. The method of claim 3, wherein the siRNA targets a nucleic acid sequence comprising a sequence as set forth in SEQ ID NO: 5, 6, 8, 9, 11, 12, or 17-108.

5. The method of claim 3, wherein the siRNA targets a nucleic acid sequence comprising a sequence as set forth in SEQ ID NO: 5, 6, 8, 9, 11, or 12.

6. The method of claim 2 wherein the hyperproliferative disorder comprises a neoplasm comprising neoplastic cells

7. The method of claim 6, wherein administration of the siRNA results in apoptosis of at least 5% of the neoplastic cell.

8. The method of claim 6, wherein the neoplasm is selected from the group of cancer of the prostate, breast, colon, lung, head and neck, pancreas, endomefrium, bladder, cervix, ovaries, squamous cell carcinoma, renal cell carcinoma, myeloid and lymphocytic leukemia, lymphoma, medullary thyroid carcinoma, melanoma, multiple myeloma, retinoblastoma, and sarcomas of the soft tissues and bone.

9. The method of claim 8, wherein the neoplasm is prostate cancer.

10. The method of claim 1 further comprising administering a Vitamin D drug.

11. The method of claim 10, wherein the Vitamin D drug comprises calcitriol.

12. The method of claim 11 , wherein the calcitriol is administered in a therapeutically effective pulse dose no more than once every three days.

13. The method of claim 11 , wherein the calcitriol is administered orally in a dose of at least 0.12 mcg/kg per day no more than once per week.

14. The method of claim 13, wherein the calcitriol is administered orally in a dose of at least 0.48 mcg/kg or about 1 mcg/kg per day no more than once per week.

15. The method of claim 6, comprising administering the IRX5 inhibitor to a subject having a neoplasm that expresses a Vitamin D receptor.

16. A method for identifying potential therapeutic agents, comprising determining IRX5 inhibitory activity of an agent, wherein inhibition of IRX5 activity by the agent identifies that the agent as a potential therapeutic agent.

17. The method of claim 16, wherein inhibition of IRX5 activity by the agent identifies that the agent as a potential therapeutic agent useful in the treatment of a hyperproliferative disorder.

18. The method of claim 17, wherein the hyperproliferative disorder comprises a neoplasm.

19. The method of claim 18, wherein the neoplasm is selected from the group of cancer of the prostate, breast, colon, lung, head and neck, pancreas, endomefrium, bladder, cervix, ovaries, squamous cell carcinoma, renal cell carcinoma, myeloid and lymphocytic leukemia, lymphoma, medullary thyroid carcinoma, melanoma, multiple myeloma, retinoblastoma, and sarcomas of the soft tissues and bone.

20. The method of claim 19, wherein the neoplasm is prostate cancer.

21. The method of claim 16, wherein the agent comprises a siRNA, a shRNA, an anti-sense nucleic acid, a ribozyme, an aptamer, a mirror-image aptamer, an IRX5 peptide, an IRX5 inhibitory antibody, or a combination thereof.

22. The method of claim 21, wherein the agent comprises a siRNA or a shRNA.

23. A method of identifying potential therapeutic agents, comprising: providing a test cell that expresses an IRX5 nucleic acid or an IRX5 protein; contacting the test cell with an agent; and determining whether the agent inhibits at least one of: expression of the IRX5 nucleic acid, or activity of the IRX5 protein; wherein inhibition of at least one of IRX5 nucleic acid expression or IRX5 protein activity identifies the agent as a potential therapeutic agent.

24. The method of claim 23, wherein the potential therapeutic agent is useful in the treatment of hyperproliferative disorder.

25. The method of claim 24, wherein the hyperproliferative disorder comprises a neoplasm.

26. The method of claim 25, wherein the neoplasm is prostate cancer.

27. An IRX5 inhibitor comprising a siRNA, a shRNA, an anti-sense nucleic acid, a ribozyme, an aptamer, a mirror-image aptamer, an IRX5 dominant negative peptide, an IRX5 inhibitory antibody, or a combination thereof.

28. The IRX5 inhibitor of claim 27, wherein the IRX5 inhibitor comprises a siRNA or a shRNA.

29. The IRX5 inhibitor of claim 28, wherein the siRNA targets a nucleic acid sequence comprising a sequence as set forth in SEQ ID NO: 5, 6, 8, 9, 11, 12, or 17-108.

30. The IRX5 inhibitor of claim 29, wherein the siRNA targets a nucleic acid sequence comprising a sequence as set forth in SEQ ID NO: 5, 6, 8, 9, 11, or 12.

31. A pharmaceutical composition comprising an IRX5 inhibitor and a pharmaceutically acceptable carrier.

32. The pharmaceutical composition of claim 31, wherein the IRX5 inhibitor comprises a siRNA, a shRNA, an anti-sense nucleic acid, a ribozyme, an aptamer, a mirror-image aptamer, an IRX5 dominant negative peptide, an IRX5 inhibitory antibody, or a combination thereof.

33. The pharmaceutical composition of claim 32, wherein the IRX5 inhibitor comprises a siRNA or a shRNA.

34. The pharmaceutical composition of claim 33, wherein the siRNA targets a nucleic acid sequence comprising a sequence as set forth in SEQ ID NO: 5, 6, 8, 9, 11, 12 or 17-108.

35. The pharmaceutical composition of claim 34, wherein the siRNA targets a nucleic acid sequence as set forth in SEQ ID NO: 5, 6, 8, 9, 11, or 12.

36. The method of claim 1 further comprising administering a chemotherapeutic agent, radiation therapy, hormone treatment or a combination thereof.

37. The method of claim 36, wherein the chemotherapeutic agents comprises an antimitotic agent.

38. The method of claim 37, wherein the antimitotic agent comprises paclitaxel, docetaxel, epothilone A, epothilone B, discodermolide, laulimalide or a combination thereof.