Inhibition of MAPK enhances the effects of pimozide on cell viability. (A) K562 cells were treated with pimozide (5μM), nilotinib (3nM), or both for 3 hours, and immunoblots were performed to phospho-MAPK and total MAPK (left); phospho-MAPK/total MAPK band intensity is shown in the right panel. (B) K562 cells were treated with pimozide (7.5μM), the MEK inhibitor U0126 (10μM), or both for 48 hours, after which viable cell number was quantitated by ATP-dependent bioluminescence. (C) Isobologram analysis was performed based on loss of cell viability for 9 different combinations of pimozide and UO126. Data points below the line indicate superadditive effects.