Transforming potential of FLT3 mutants in Ba/F3 cells. All experiments were performed in triplicates. Error bars represent standard deviation of the mean. (A) Ba/F3 cells expressing indicated FLT3 constructs were seeded at a density of 4 × 104 cells per mL in the presence or absence of 10 ng/mL IL-3 and 100 ng/mL FL. Viable cells were counted by trypan blue exclusion after 72 hours. (B) Ba/F3 cells transduced with the indicated FLT3 constructs were seeded at a density of 2 × 105 cells per mL in 0.1% WEHI-conditioned medium and cultured for 10 days. After 72 hours, cells were cleared from previous medium and resuspended in 0% WEHI-conditioned medium. Control cells were cultured in 10 ng/mL IL-3–supplemented medium. (C) Cells were cultured in the presence or absence of 10 ng/mL IL-3 for 72 hours and stained with Annexin V and 7-aminoactinomycin D. The percentage of apoptotic cells was determined by fluorescence-activated cell sorter analysis.