MLH1 and colorectal carcinoma: MSI-H CRC cells carrying dMMR harbor silent expression of mismatch repair genes through either germline mutations of MMR genes such as MutL homolog 1 (MLH1), MutS homolog 2 (MSH2), MSH6, and Postmeiotic segregation increased 2 (PMS2), or MLH1 promoter hypermethylation [36,37].