MLH1 and xeroderma pigmentosum: Many investigations have found cancer associated genes including cyclin-dependent kinase inhibitor 2A (p16), O6-methylguanine-DNA methyltransferase (MGMT), xeroderma pigmentosum group C (XPC), MutL homolog 1 (MLH1), breast cancer 1 and 2 ( BRCA1 and BRCA2 ), death associated protein kinase 1 (DAPK1), retinoic acid receptor β (RARβ), E-CADHERIN, CYCLIN A1, p14, p15, p73, RAS association domain family (RASSF1A) and APC genes are hypermethylated in cancers [48–51].