CDK4 and cancer: In the preneoplastic livers of PML−/−HBsAgtg/0 mice by 3 months of age, we observed an exceptionally high prevalence (>50%) of mutations in the cancer drivers Ctnnb1 (which encodes β-catenin of the Wnt signaling cascade), Trp53 (which encodes p53 and maintains genomic integrity), Cdk4 (which drives cell cycle progression) and Mllt4 (which contributes to chromatin remodeling).