TP53 and neoplasm: We observed a statistically significant difference between the MMTV-Hras/p53-/- and MMTV-Hras/p53R172H/R172H mice in age of tumor onset (p = 0.0261, Log-rank test), with a slightly delayed tumor onset in the MMTV-Hras/p53R172H/R172H mice.