DNMT1 and colorectal carcinoma: The oligopeptide transporter solute carrier family 15 member 1 (SLC15A1) is an intestine-specific transporter protein, and DNA methyltransferase 1 (DNMT1) mediates hypermethylation of the proximal promoter region of the PEPT1 gene, which in turn leads to transcriptional repression and increased sensitivity of CRC to anticancer drugs [39].