Assessment of caspase-3 enzymatic activity in TRAIL-sensitive and -resistant cells.

Caspase-3 enzymatic activity was measured with a caspase-3 intracellular activity assay kit in TRAIL-sensitive (MM.1S, panel A), moderately resistant (ARH-77, panel B), and highly resistant (IM-9, panel C) cells treated with (shaded curves) or without (unshaded curves) TRAIL (300 ng/mL) for 5 hours. A large population of cells was found to be positive for caspase-3 activity in MM.1S, but not ARH-77 or IM-9 cells treated with TRAIL.