Requirement for antiapoptotic function in leukemia maintenance. (A) In vitro–generated Mcl-1^f/fArf^−/− p185⁺ cells stably expressing either vector or ectopic Mcl-1 were transduced with Cre-IRES-GFP to delete the endogenous Mcl-1. The total number of GFP⁺ cells was measured every 24 hours. IL-7 was used at a final concentration of 20 ng/mL. Each point represents the average of 3 independent experiments (n = 3), and the error bars denote the SEM. (B) Immunoblot analysis of p185⁺Mcl-1^f/fArf^−/− pre–B cells before and after Cre-IRES-GFP transduction was performed. Lysates were western blotted for MCL-1, Cre, and actin (loading control). (C) Mcl-1^f/fArf^−/− p185⁺ pre–B cells stably expressing indicated constructs were transduced with Cre-IRES-GFP to delete endogenous Mcl-1. The total number of GFP⁺ cells was measured every 24 hours. Each point represents the average of 3 independent experiments (n = 3), and the error bars denote the SEM. (D) Immunoblot analysis shown for Mcl-1^f/fArf^−/− p185⁺ pre–B cells before and after Cre-IRES-GFP transduction for MCL-1, BCL-2 (human-specific antibody), BCL-X_L, Cre, and Actin (loading control).