Caspase-9 expression and processing in NSCLC and SCLC cell line. A) Western blots showing the level of expression of procaspase-9 and Apaf-1 in a panel of NSCLC and SCLC cell lines. β-actin was used as control for protein loading. B) H460 and GLC4 cells were treated with IC80 concentrations of cisplatin for 24 and 48 h or C) only for 48 h and cellular extracts were generated. Extracts were incubated for 45 min at 37°C in the presence (+) or absence (-) of exogenously added cytochrome c and dATP. Subsequently, caspase-9 was immunoprecipitated and visualized by western blotting or activation of caspase-9 was measured by the cleavage of the fluorogenic substrate LEHD-AFC, respectively.