Figure 3: Involvement of caspase-like proteases in Apo2L/TRAIL-induced apoptosis. (a) Percentage-specific apoptosis in VH-64 cells treated for 72 hours in the absence (□) and presence (■) of IGF1 (100 ng/mL) and subsequently for 30 min with varying concentrations of z-DEVD-fmk, followed by incubation with Apo2L/TRAIL (50 ng/ml; 8 hours). Error bars: mean ± SD of triplicate determinations from 2 independent experiments. (b) Fold increase in the activity of caspase-8 (C-8), caspase-9 (C-9), and caspase-3/7 (C-3/7) in cells treated for the indicated times with IGF1 (100 ng/mL), followed by incubation in the absence () and presence (●) of Apo2L/TRAIL (50 ng/mL; 4 hours). Values of vehicle-treated controls for caspase-8, caspase-9, and caspase-3/7 activity were set to 1. Asterisks: *, **; error bars: mean ± SD of triplicate determinations from 3 independent experiments.