Evaluation of TRAIL-induced caspase activity in HL60.

Cells were treated with TRAIL (0.2 μg/mL) for the indicated times. (A) Caspase activity was evaluated on cell lysates by using either CPP32 or ICE substrates. Data are expressed as a percentage of control (His peptide–treated) cells. Data represent the means ± SD of 4 independent experiments performed in duplicate. (B) Caspase activation induced by TRAIL, in the presence or absence of z-VAD-fmk inhibitor of effector caspases, has been evaluated by flow cytometry following incubation with CaspACE FITC-VAD-FMK in situ marker. Data are expressed as percentage of positive (fluorescent) cells. Analysis was performed after 6 hours of TRAIL treatment by gating viable cells. Data represent the means ± SD of 4 independent experiments performed in duplicate.