Figure 5

Caspase-9 is functionally relevant in etoposide-induced caspase-8 activation and apoptosis. A and B, effects of caspase inhibitors on caspase-8 activation and the induction of apoptosis by etoposide in HNSCC cell lines. HOC313/c8_3 cells and Ca9-22 cells were incubated at 32.5°C and 37°C respectively with the indicated caspase inhibitors (80 μM) for 1.5 h, followed by treatment with cisplatin (10 μg/ml) or etoposide (100 μg/ml) for 24 h. The DNA profiles were analyzed by LSC as in Figure 2B (A). Caspase-8 activity was analyzed by Caspase-Glo 8 assay (B). Results are expressed as fold induction compared with untreated control. The bars represent the SD. The asterisk indicates a significant difference (p < 0.05) between the presence and absence of Ac-LEHD-CHO in etoposide-treated cells (t-test).