ARRY-520-induced cell death is mediated via the mitochondrial apoptotic pathway. HL-60 and HL-60Bcl-2 cells were treated with ARRY-520. Cell cycle distribution was determined at 24 hours by PI staining, changes in MMP at 24 hours by CMXRos and MitoTracker Green staining, and apoptosis by annexin V/7-AAD staining (A). HL-60 and HL-60Bcl-2 cells were treated with ARRY-520, ABT-737, or both and cell death was determined at 24 hours by annexin V/7-AAD staining (B). HL-60 cells were treated with 10 nM ARRY-520 for various time points, and Bim and caspase-3 levels were determined by western blot analysis (C). ABT, ABT-737; AR, ARRY-520.