Caspase-9-deficient BLIN-4L cells show increased apoptotic sensitivity to staurosporine. Cells were electroporated with control or caspase-9 siRNA and allowed to recover as described in “Materials and methods.” After 3 days, the 2 treated populations were removed from recovery medium and assayed immediately for annexin V binding (0 h value). The remaining cells were cultured for 6 hours in X-VIVO 10 containing DMSO (vehicle control [CONT]), 1.0 μM etoposide (ETOP), or 0.02 μM staurosporine (STSP). The etoposide and staurosporine values represent the percentage of total annexin V⁺ events (PI⁺ and PI^-) minus the number present in DMSO, in order to eliminate the inherent difference in the apoptotic sensitivity of the 2 populations. The results represent the mean ± SD from 3 separate experiments. ^*P < .008 compared with control siRNA treatment (Wilcoxon rank sum method).