The caspase-3 inhibitor zDEVD-fmk blocks drug-induced processing of caspase-8 and inhibits DNA fragmentation in BJAB cells.

BJAB cells were either incubated in control medium (Co) or stimulated with 0.1 μg/mL Taxol (T) or 1 μg/mL epirubicin (E). Some cultures were preincubated with 10 μM caspase-3 inhibitor zDEVD-fmk (I) 2 hours before drug treatment. After 48 hours of incubation, Western blot analyses were performed with antihuman caspase-3 (A) and antihuman caspase-8 antibodies (B). Positions of molecular mass markers are indicated at the left. Arrows indicate the positions of procaspase-3 (*), the 17-kd active subunit of caspase-3 (**), procaspase-8 (#), and the 18-kd active subunit of caspase-8 (##). The experiments were repeated and yielded similar results. Additionally, DNA fragmentation (C) was measured in the cultures after 48 hours of drug treatment. Values are given as percentage of specific apoptosis ± SD (n = 3).