The expression of Bcl-x(L) in FLT3-ITD mutants restores the SU5614- and daunorubicin-resistant phenotype in Ba/F3 cells. Ba/F3 cells transduced with the FLT3-ITD (▪) or FLT3-ITD and Bcl-x(L) constructs (○) were incubated with different concentrations of SU5614 (A) or daunorubicin (B) for 24 hours and were analyzed by flow cytometry after staining with annexin V-PE and 7-AAD. Values represent mean and standard deviation from 3 independent experiments. (C) Bcl-x(L) expression in cells transduced with empty vector, FLT3-WT, FLT3-ITD, FLT3-ITD and Bcl-x(L), or Bcl-x(L) was determined by Western blot analysis. Identical protein loading in all lanes was confirmed by immunoblotting using an anti–β-actin antibody.