Figure 3. The synergistic effect of PEITC on CDDP-induced apoptosis in HeLa cells.
A, top: phase contrast photomicrographs of cells treated with DMSO (vehicle control), 10 μM CDDP, 5 μM PEITC, and 5 μM PEITC plus 10 μM CDDP for 24 h. Note the presence of massive cell death in cells treated with 5 μM PEITC plus 10 μM CDDP. Middle: caspase-3 activity analysis in cells treated with 5 μM PEITC, 10 μM CDDP, or the combination for 24 h. Bottom: Effect of PEITC plus CDDP on PARP cleavage. Subconfluent cells were incubated with 5 μM PEITC, 10 μM CDDP alone or the combination, PARP expression and cleavage was examined in whole cell lysates collected 8 and 24 h after treatment and assessed by Western Blot analysis using an anti-PARP monoclonal antibody. B, enhanced ERK activation after the combination treatment of PEITC plus CDDP in HeLa cells. Cells were treated with either 10 μM CDDP alone, 5 μM PEITC alone, or 5 μM PEITC plus 10 μM CDDP for 8 and 24 h. Western Blot analysis shows enhanced ERK activation in PEITC plus CDDP-treated cells. C, MEK1/2 inhibitor blocks apoptosis induced by the combination of PEITC and CDDP. Pretreatment with MEK1/2 inhibitor U0126 inhibits ERK (lane 2) and caspase-3 activation caused by the combination of PEITC and CDDP (top). Western Blot analysis shows reduced PARP cleavage in cells treated with U0126 prior to PEITC plus CDDP (bottom). D, PARP cleavage shows that JNK inhibitor SP600125 and p38 inhibitor SB203580 have no effect on apoptosis induced by the combination of PEITC and CDDP in HeLa cells.