Loss of 1 allele of Mcl-1 significantly delays thymic lymphoma development in p53^−/− mice. (A) Tumor-free survival comparing p53^−/− (control; n = 27) and p53^−/−;Mcl-1^+/− mice (n = 17; log-rank Mantel-Cox test, P = .0006). (B) Incidence in % of thymic lymphoma, splenomegaly, and other pathologies (eg, sarcoma) in p53^−/− (n = 11) and p53^−/−;Mcl-1^+/− mice (n = 17). (C) Representative immunophenotyping of primary thymic lymphoma samples from p53^−/− and p53^−/−;Mcl-1^+/− mice (gated on PI⁻ and TCRβ⁺ large cells). (D) Analysis of the proteins indicated by western blotting of primary thymic lymphoma samples from mice of the indicated genotypes (representative of 7 samples each). Probing for HSP70 was used as a loading control.