Genetic analysis of Cdk6 R31C mice. (A) Tumor-free survival of wild-type and Cdk6^R/R mice. (B) Incidence of tumors in the indicated genotypes. (C) Tumor-free survival of Cdk6 R31C mice in p53-heterozygous or null backgrounds. (D) Incidence of tumors of different origins in the indicated genotypes. The presence of the Cdk6 R31C allele results in increased incidence of sarcomas and hematopoietic tumors only in a p53-heterozygous background. See supplemental Table 1 for details. (E) Tumor-free survival of Cdk4^R/R; Cdk6^R/R or double Cdk4^R/R; Cdk6^R/R mutant mice. (F) Tumor distribution in mutant mice with the indicated genotypes. See Table 1 for details. Long-rank test; *P < .05; **P < .01; ***P < .001.