Catechol O-methyltransferase (COMT; EC:2.1.1.6) catalyzes the synthesis of S-Adenosyl-homocysteine (SAH) from S-Adenosyl-methionine (SAM), the latter being a major methyl donor in transmethylation reactions that can downregulate the expression of oncogenic promoters by reversing DNA hypomethylation, thereby inhibiting tumor growth43. This evidence concerns the gene COMT and neoplasm.