Multi-functional protein Glycine N-methyltransferase (GNMT, EC2.1.1.20, localized to chromosome 6p12), affects genetic stability by a) regulating the ratio of S-adenosylmethionine (SAM) to S-adenosylhomocystine (SAH) and b) binding to folate. Based on the following observations, GNMT is classified as a tumor susceptibility gene: a) diminished GNMT expression levels in both human hepatocellular carcinoma (HCC) cell lines and tissues; b) genotypic analyses of several human GNMT gene polymorphisms showed a loss of heterozygosity in 36-47% of the genetic markers in HCC tissues and also related to the susceptibility of prostate cancer; c) GNMT binds to environmental carcinogens such as benzo(a)pyrene (BaP) and aflatoxin B1 (AFB1) and protect the liver cells by inhibiting DNA-adduct formation.