MLH1 and colorectal carcinoma: Mismatch repair genes are silently expressed in MSI-H CRC cells due to germline mutations in genes such as MutL homolog 1 (MLH1), MutS homolog 2 (MSH2), MSH6, and Postmeiotic segregation increased 2 (PMS2), or MLH1 promoter hypermethylation.