Inhibition of apoptosis, PS externalization, and CPP32 processing by inhibitors of ICE family proteases. U937 cells were treated with 10 μg/mL etoposide in the presence of indicated concentrations of Z-Asp (circles) and Z-VAD (squares) for 4 hours. The development of apoptosis (open symbols) and PS externalization (solid symbols) were analyzed using a flow cytometer (A), and CPP32 processing was examined by Western blot analysis (B). CPP32 processing to the p20 and p17 fragments is presented. Lane 1, no inhibitor; lanes 2 through 4, Z-Asp at 10, 30, and 100 μg/mL, respectively; lanes 5 through 7, Z-VAD at 10, 30, and 100 μg/mL, respectively. The experiments were repeated three times and similar results were obtained.