Evaluation of caspase inhibitors on the combined cytotoxicity of IR (1.5 Gy) 6 hours before the addition of TRAIL (1 μg/mL).

Cells were pretreated with z-VAD-fmk or z-FA-fmk peptides (20 μM each), irradiated with 1.5 Gy and, after 6 hours, supplemented with TRAIL (1 μg/mL). Viable cells were counted by trypan blue dye exclusion 24 hours after irradiation. Data are expressed as percentage of control (His6-tag peptide-treated) cells and represent the mean ± SD of 4 independent experiments performed in duplicate.