ABT-737 further enhances the pro-apoptotic effect of the AZD8055/selumetinib combination treatment in AML cells. A, AML cells were treated with AZD8055, selumetinib, ABT-737, or the indicated combinations for 48 hours, and examined for apoptosis induction. B, U937 cells were treated as described above and examined for apoptosis induction. ** P < 0.01; *** P < 0.001. C, KG-1 and OCI/AML3 cells were treated with ABT-737, AZD8055 plus selumetinib, or both at the indicated concentrations (in μmol/L) for 6 hours, and Bcl-2 protein was pulled down with anti-Bcl-2 antibody-conjugated A/G beads. Bcl-2–binding Bax protein expression was measured using immunoblotting. A 10% Bcl-2 input of immunoprecipitated fractions is shown as a loading control for Bcl-2 protein level. IP, immunoprecipitation; WB, immunoblot. D, KG-1 and OCI/AML3 cells were treated with ABT-737, AZD8055 plus selumetinib, or both for 24 hours, and the cells were lysed to assess expression of apoptosis-related Bcl-2 family members in mitochondrial, cytosol, and whole-cell fractions via immunoblotting. Casp, caspase; EL, extra-long; L, long and S, short.