Potentiation of mouse BCR-ABL⁺leukemia to combining TKI and small-molecule BCL-2 inhibitors. (A) In vitro–generated Mcl-1–deleted Arf^−/− p185⁺ cells stably expressing the indicated constructs were treated with indicated doses of navitoclax (ABT-263) for 24 hours after which the percent viable cells was determined (PI-negative cells were scored as viable). Each point represents the average of 3 independent experiments, and the error bars denote the SEM. p185⁺Arf^−/− cells serve as a control. (B) Arf-null p185⁺ cells were treated with navitoclax for 24 hours at indicated doses. Lysates were immunoprecipitated with anti-BIM antibody, and immune complexes were resolved and western blotted for MCL-1, BCL-2 (human specific antibody), BCL-X_L, BIM, PARP, and actin (loading control). Endogenous BIM serves as the control for equal immunoprecipitation. (C-D) p185⁺Arf^−/− cells were treated with IM (C) or DAS (D) for 24 hours at indicated doses. Lysates were immunoprecipitated with anti-BIM antibody, and immune complexes were resolved and western blotted for MCL-1, BCL-2, BCL-X_L, BIM, PARP, and actin (loading control). Endogenous BIM served as the control for equal immunoprecipitation. (E-F) p185⁺Arf^−/− cells were treated with indicated doses of navitoclax and/or IM (E) or DAS (F) for 24 hours after which the percent viable cells was determined. Annexin-V/PI–negative cells were scored as viable. IL-7 was added to a final concentration of 20 ng/mL. Bars represent the average of 3 independent experiments done in triplicate, and the error bars denote the SEM. Asterisk (*) indicates P < .001 by 2-way analysis of variance with a Bon Ferroni posttest between treatments linked with horizontal line.