As a model system we used the HCT116 chromosomally stable colorectal carcinoma cell line (HCT-wt) and its isogenic derivatives p53-/- and p21-/- (HCTp53KO, HCTp21KO), which have both p53 and p21waf1 alleles disrupted [14]. The gene discussed is TP53; the disease is colorectal carcinoma.