Stimulation of ICE-like proteolytic activity after CD95 ligation and chemotherapeutic drug treatment in CEM cells. CEM cells were incubated for the indicated times with anti–APO-1 (A), CR (B), DX (C), and MT (D) at concentrations indicated. Ten minutes before harvest, cells were permeabilized by a short hypotonic shock and incubated with 50 μmol/L of the fluorogenic ICE substrate. Cells were analyzed in parallel by FACS for induction of cell death and ICE proteolytic activity. The data represent the mean ± SD from three experiments with duplicate samples. Similar data were obtained in SHEP cells (data not shown).