Fig. 3. Rescue of apoptosis using exogenous and endogenous inhibitors. A, proliferation of E1A/ras-transformed cells was assessed 24 h after combined treatment with STP (20 nM) and IR (5 Gy), with or without preincubation with increasing concentrations of Z-VAD-FMK. B, cell proliferation of E1A/ras-transformed MEFs overexpressing bcl-2 () and cells carrying only a control vector () was measured 24 h after combined treatment with IR (5 Gy) in the presence of increasing doses of STP (520 nM). C, caspase-3-like activities were measured in Bcl-2-overexpressing cells () and control cells () as described in the legend to Fig. 2 .