CDKN2A and cancer: However, since mice lacking both the p16INK4a and p21Waf1/Cip1 genes (p16/p21‐double knockout (DKO) mice) begin to die of cancer at around 12 months of age and all die by 17 months (Kawamoto et al., 2023), it is impossible to fully age p16/p21‐DKO mice.