RB1 and cancer: Interestingly, unlike many other tumor suppressor genes, such as BRCA1, RB, and APC, that are usually inactivated by deletions or truncating mutations in cancers, majority of p53 mutations in cancers are missense mutations, which leads to the production of full-length mutp53 proteins with only one amino acid substitution (Freed-Pastor and Prives, 2012; Muller and Vousden, 2013; Yue et al., 2017b; Mantovani et al., 2019).