Viable cell number and active caspase-3 expression after incubation of transduced c-kit⁺, Lin^– cells with GM-CSF and SCF for 72 hours. (A) GFP⁺, c-kit⁺, Lin^– cells were isolated using FACS following retrovirus infection and were incubated with rmGM-CSF and rmSCF. Viable cells were enumerated after 72 hours by trypan blue dye exclusion. Data are the average of 3 experiments. (B) Intracellular active caspase-3 expression analysis of the same samples shown in panel A. The percentage increase in active caspase-3 in p21^+/+ cells transduced with wild-type or T34A Survivin was compared with p21^+/+ cells transduced with empty vector. P21^–/– cells transduced with Survivin constructs were compared with p21^–/– cells transduced with empty vector. Data are the average of 3 experiments.