Classical tumour suppressor genes and genes involved in chemosensitivity, such as hMLH1, p16, p15, Rb, VHL, E-cadherin, GSTP1, and BRCA1, or the DNA repair gene MGMT, undergo epigenetic inactivation by hypermethylation of their regulatory regions [36-39]. This evidence concerns the gene CDKN2A and neoplasm.