The combination of pimozide and imatinib leads to enhanced effects on STAT5 inhibition and apoptosis. (A) KU812 cells were treated with pimozide (5μM), imatinib (50nM), or both for 3 hours, after which immunoblot analysis was performed for phospho-STAT5 and total STAT5. (B) KU812 cells were treated with pimozide (5μM), imatinib (50nM), or both for 48 hours, after which viable cell number was measured using an ATP-dependent bioluminescence assay. (C) Isobologram analysis was performed based on change in viable cell number for 9 different combinations of pimozide and imatinib. Data points below the line indicate superadditive effects. (D) KU812 cells were treated with pimozide (5μM), imatinib (50nM), or both for 48 hours, after which flow cytometric analysis was performed. The percentage of cells staining with annexin V is shown. Data are representative of 3 independent experiments.