A, U937, K562 and MV411 cells were incubated with increasing doses of ABT-263 (0.7 nM to 45 μM) for 48 hours and the relative numbers of viable cells were determined by reduction of alamar blue. All data points represent the compilation of at least biological triplicates. B, U937 cells were treated with 1.6 μM of ABT-263, or vehicle (DMSO), for 8 and 24 hours and the total amount of cellular ceramides were determined by HPLC-MS/MS. C, K562 cells were treated with 150 nM of ABT-263, or vehicle, for 8 and 24 hours and the total amount of cellular ceramides were determined by HPLC-MS/MS. D, MV411 cells were treated with 50 nM of ABT-263, or vehicle (DMSO), for 8 and 24 hours and the total amount of cellular ceramides were determined by HPLC-MS/MS. D, ***, P=<0.0005; **, P=<0.005; *,p=<0.05.