Acute loss of both alleles of Mcl-1 significantly prolongs survival of mice bearing p53^−/− lymphomas. This experiment was conducted as described in Figure 5A. (A) Lymphoma-free survival of the mice that had been transplanted with lymphoma cells of the genotypes indicated and treated with either tamoxifen (solid line to delete the floxed Mcl-1 alleles) or that had been left untreated (dashed line; negative control). (B) Analysis of the proteins indicated by western blotting of transplanted thymic lymphoma samples of the indicated genotypes (representative of 3 samples each) that had grown in recipients treated with tamoxifen (tam) or recipients that had been left untreated (ctrl). Probing for actin was used as a loading control. Lanes 1 and 2 are the same samples as shown in lanes 1 and 2 of Figure 5C and are presented here for comparison.