Genomic DNA hypomethylation, a characteristic of most cancers, is present in peripheral leukocytes of individuals who are homozygous for the C677T polymorphism in the methylenetetrahydrofolate reductase gene.

DNA methylation is an epigenetic feature of DNA that influences cellular development and function, and aberrations of DNA methylation are a candidate mechanism for the development of cancer. Methylenetetrahydrofolate reductase (MTHFR) catalyzes the synthesis of 5-methyltetrahydrofolate, the methyl donor for methionine synthesis and the precursor of S-adenosylmethionine. S-adenosylmethionine is the universal methyl donor for methylation reactions, including that of DNA methylation. In the present study, we investigated whether a common C677T mutation in the MTHFR gene, which results in reduced enzyme activity in vitro, affects genomic DNA methylation. We selected 9 subjects homozygous for the wild-type MTHFR and 10 subjects homozygous for the mutation (T/T). Genomic DNA methylation was determined by an established enzymatic assay that measures the capacity of DNA to accept methyl groups in vitro, which is inversely related to endogenous methylation. DNA from subjects with the T/T MTHFR genotype had a significantly higher methyl group acceptance capacity (12,615 +/- 1836 dpm/2 microg of DNA) compared with wild-type MTHFR (7843 +/- 1043 dpm/2 microg of DNA; P < 0.05), indicating DNA hypomethylation in the T/T genotype. Furthermore, DNA methylation was directly and significantly related to RBC folate concentrations in persons with the T/T genotype, but not in those with wild-type MTHFR. These data are consistent with prior observations, which suggest that the T/T genotype is associated with impaired MTHFR activity in vivo and that the cellular impact of this impairment is determined, in part, by folate status. The relationship of genomic DNA hypomethylation in persons with the T/T MTHFR genotype to the development of cancer remains to be defined.

[1]  J. Mason,et al.  Moderate folate deficiency does not cause global hypomethylation of hepatic and colonic DNA or c-myc-specific hypomethylation of colonic DNA in rats. , 1995, The American journal of clinical nutrition.

[2]  D. Wilcken,et al.  Common methylenetetrahydrofolate reductase gene mutation leads to hyperhomocysteinemia but not to vascular disease: the result of a meta-analysis. , 1998, Circulation.

[3]  M. Ehrlich,et al.  The 5-methylcytosine content of DNA from human tumors. , 1983, Nucleic acids research.

[4]  Y. Sako,et al.  Determination of free and total homocysteine in human plasma by high-performance liquid chromatography with fluorescence detection. , 1987, Journal of chromatography.

[5]  K. Kinzler,et al.  DNA methylation and genetic instability in colorectal cancer cells. , 1997, Proceedings of the National Academy of Sciences of the United States of America.

[6]  R. Rozen.  Genetic Predisposition to Hyperhomocysteinemia: Deficiency of Methylenetetrahydrofolate Reductase (MTHFR) , 1997, Thrombosis and Haemostasis.

[7]  R. Matthews,et al.  A candidate genetic risk factor for vascular disease: a common mutation in methylenetetrahydrofolate reductase , 1995, Nature Genetics.

[8]  A. Bird.  CpG-rich islands and the function of DNA methylation , 1986, Nature.

[9]  A. Folsom,et al.  Prospective study of coronary heart disease incidence in relation to fasting total homocysteine, related genetic polymorphisms, and B vitamins: the Atherosclerosis Risk in Communities (ARIC) study. , 1998, Circulation.

[10]  I. Pogribny,et al.  Folate deficiency in rats induces DNA strand breaks and hypomethylation within the p53 tumor suppressor gene. , 1997, The American journal of clinical nutrition.

[11]  J. Sambrook,et al.  Molecular Cloning: A Laboratory Manual , 2001 .

[12]  M. Leppert,et al.  Methylenetetrahydrofolate reductase, diet, and risk of colon cancer. , 1999, Cancer epidemiology, biomarkers & prevention : a publication of the American Association for Cancer Research, cosponsored by the American Society of Preventive Oncology.

[13]  J. Selhub,et al.  A common mutation in the methylenetetrahydrofolate reductase gene is associated with an accumulation of formylated tetrahydrofolates in red blood cells. , 1998, Proceedings of the National Academy of Sciences of the United States of America.

[14]  L. Poirier,et al.  Breaks in genomic DNA and within the p53 gene are associated with hypomethylation in livers of folate/methyl-deficient rats. , 1995, Cancer research.

[15]  I. Pogribny,et al.  Moderate folate depletion increases plasma homocysteine and decreases lymphocyte DNA methylation in postmenopausal women. , 1998, The Journal of nutrition.

[16]  J. Buckley,et al.  The role of DNA methylation in cancer. , 1990, Advances in cancer research.

[17]  E. Trabetti,et al.  Methylenetetrahydrofolate reductase C677T mutation, plasma homocysteine, and folate in subjects from northern Italy with or without angiographically documented severe coronary atherosclerotic disease: evidence for an important genetic-environmental interaction. , 1998, Blood.

[18]  Rudolf Jaenisch,et al.  Role for DNA methylation in genomic imprinting , 1993, Nature.

[19]  E. Rimm,et al.  A methylenetetrahydrofolate reductase polymorphism and the risk of colorectal cancer. , 1996, Cancer research.

[20]  R. Matthews,et al.  The structure and properties of methylenetetrahydrofolate reductase from Escherichia coli suggest how folate ameliorates human hyperhomocysteinemia , 1999, Nature Structural Biology.

[21]  W. Willett,et al.  Methylenetetrahydrofolate reductase polymorphism, dietary interactions, and risk of colorectal cancer. , 1997, Cancer research.

[22]  P. Reitsma,et al.  The effect of a common methylenetetrahydrofolate reductase mutation on levels of homocysteine, folate, vitamin B12 and on the risk of premature atherosclerosis. , 1998, Atherosclerosis.

[23]  E. Stokstad,et al.  Folic Acid Metabolism In Health And Disease , 1990 .

[24]  T. Kundu,et al.  CpG islands in chromatin organization and gene expression. , 1999, Journal of biochemistry.

[25]  N. Ozer,et al.  Methylene tetrahydrofolate reductase genotype and the risk and extent of coronary artery disease in a population with low plasma folate , 1999, Heart.

[26]  I. Rosenberg,et al.  Relation between folate status, a common mutation in methylenetetrahydrofolate reductase, and plasma homocysteine concentrations. , 1996, Circulation.

[27]  E. Farber,et al.  The induction of liver cancer by dietary deficiency of choline and methionine without added carcinogens. , 1984, Carcinogenesis.

[28]  A. Giuliano,et al.  Global DNA hypomethylation increases progressively in cervical dysplasia and carcinoma , 1994, Cancer.

[29]  K. L. Hoover,et al.  Hepatocarcinogenesis in rats fed methyl-deficient, amino acid-defined diets. , 1983, Carcinogenesis.

[30]  G. Morgan,et al.  Polymorphisms in the methylenetetrahydrofolate reductase gene are associated with susceptibility to acute leukemia in adults. , 1999, Proceedings of the National Academy of Sciences of the United States of America.

[31]  P. Wong,et al.  Thermolabile Defect of Methylenetetrahydrofolate Reductase in Coronary Artery Disease , 1993, Circulation.

[32]  P. Jones,et al.  Involvement of DNA methylation in human carcinogenesis. , 1998, Biological chemistry.

[33]  C. Ulrich,et al.  Colorectal adenomas and the C677T MTHFR polymorphism: evidence for gene-environment interaction? , 1999, Cancer epidemiology, biomarkers & prevention : a publication of the American Association for Cancer Research, cosponsored by the American Society of Preventive Oncology.

[34]  P. Frosst,et al.  Molecular genetic analysis in mild hyperhomocysteinemia: a common mutation in the methylenetetrahydrofolate reductase gene is a genetic risk factor for cardiovascular disease. , 1996, American journal of human genetics.

[35]  S. S. Kang,et al.  Intermediate homocysteinemia: a thermolabile variant of methylenetetrahydrofolate reductase. , 1988, American journal of human genetics.

[36]  J. Selhub,et al.  The pathogenesis of homocysteinemia: interruption of the coordinate regulation by S-adenosylmethionine of the remethylation and transsulfuration of homocysteine. , 1992, The American journal of clinical nutrition.