Cks1 knockout does not change the occurrence of p53 and/or p19^ARFabnormalities in LMP2A/λ-MYC and λ-MYC tumors. The status of p53 and p19^ARF expression in lymph node tumors from the indicated mouse genotype. (A) Representative immunoblots of p53 and p19^ARF. (B) Combined data from several independent experiments. Statistical analyses were performed with Fisher’s exact test by comparing the frequency of p53 and p19^ARF abnormalities in Cks1^+/+ vs Cks1^−/− within the LMP2A/λ-MYC or λ-MYC background. p53⁺ and p19⁻, baseline p53 and p19^ARF levels as indicated by immunoblots; p53⁻, undetected baseline level of p53; p53⁺⁺, aberrant p53 accumulation at ∼53 kDa; p19⁺, abnormal accumulation of p19^ARF. (C) The number of tumor-free days in each indicated genotype. Medians with 95% confident intervals of ratios are indicated. Survival analyses were performed with both the log-rank (Mantel-Cox) test and Gehan-Breslow-Wilcoxon test by comparing the tumor-free days of the subgroups with (+) vs without (–) p53 and p19^ARF abnormalities for each genotype. NS, not significant.