5-methyltetrahydrofolate and Liver-Neoplasms

Topics: Adenocarcinoma; Adult; Aged; Clinical Trials as Topic; Colonic Neoplasms; Drug Therapy, Combination; Female; Fluorouracil; Humans; Liver Neoplasms; Lung Neoplasms; Male; Middle Aged; Pelvic Neoplasms; Rectal Neoplasms; Tetrahydrofolates

Glycine N-methyltransferase (GNMT) is a folate binding protein commonly diminished in human hepatoma yet its role in tumor development remains to be established. GNMT binds to methylfolate but is also inhibited by it; how such interactions affect human carcinogenesis is unclear. We postulated that GNMT plays a role in folate-dependent methyl group homeostasis and helps maintain genome integrity by promoting nucleotide biosynthesis and DNA repair. To test the hypothesis, GNMT was over-expressed in GNMT-null cell lines cultured in conditions of folate abundance or restriction. The partitioning of folate dependent 1-carbon groups was investigated using stable isotopic tracers and GC/MS. DNA damage was assessed as uracil content in cell models, as well as in Gnmt wildtype (Gnmt(+/+)), heterozygote (Gnmt(+/-)) and knockout (Gnmt(-/-)) mice under folate deplete, replete, or supplementation conditions. Our study demonstrated that GMMT 1) supports methylene-folate dependent pyrimidine synthesis; 2) supports formylfolate dependent purine syntheses; 3) minimizes uracil incorporation into DNA when cells and animals were exposed to folate depletion; 4) translocates into nuclei during prolonged folate depletion. In conclusion, loss of GNMT impairs nucleotide biosynthesis. Over-expression of GNMT enhances nucleotide biosynthesis and improves DNA integrity by reducing uracil misincorporation in DNA both in vitro and in vivo. To our best knowledge, the role of GNMT in folate dependent 1-carbon transfer in nucleotide biosynthesis has never been investigated. The present study gives new insights into the underlying mechanism by which GNMT can participate in tumor prevention/suppression in humans.

Topics: Adenosine; Animals; Carbon Radioisotopes; Carcinoma, Hepatocellular; Cell Nucleus; Cells, Cultured; Chromatography, High Pressure Liquid; Dietary Supplements; DNA Damage; DNA Methylation; Female; Fluorescent Antibody Technique, Indirect; Folic Acid; Glycine N-Methyltransferase; Hepatocytes; Homocysteine; Humans; Liver; Liver Neoplasms; Male; Methylenetetrahydrofolate Dehydrogenase (NADP); Mice; Mice, Knockout; Minor Histocompatibility Antigens; Protein Transport; Purines; Pyrimidines; S-Adenosylhomocysteine; S-Adenosylmethionine; Tetrahydrofolates; Uracil

Thirty-eight patients with advanced colorectal adenocarcinoma were treated with the following regimen: N5-10-methyltetrahydrofolate (MTHF) (200 mg/m2/day) and 5-fluorouracil (5-FU) (375 mg/m2/day) given concomitantly, consecutively for 5 days, every 4 weeks, in order to evaluate the potential advantage derived from the biochemical enhancement of cytotoxic activity of 5-FU by high-dose reduced folates. Of 33 evaluable patients (six of whom had received prior 5-FU chemotherapy) three untreated patients achieved a partial response (9.1%) lasting 84, 281 and 401 days; 24 patients (72.7%) had stable disease lasting a median of 150 days (range 60-304 days). The overall toxicity was acceptable: two patients had severe cardiac symptoms. Pharmacokinetics and biochemical studies seem necessary to determine the optimal dosage and timing of 5-FU and folates.

Topics: Adenocarcinoma; Adult; Aged; Antineoplastic Combined Chemotherapy Protocols; Colonic Neoplasms; Drug Evaluation; Female; Fluorouracil; Humans; Liver Neoplasms; Lung Neoplasms; Male; Middle Aged; Rectal Neoplasms; Tetrahydrofolates

Topics: Animals; Asialoglycoprotein Receptor; Asialoglycoproteins; Biological Transport; Carcinoma, Hepatocellular; Cell Line; Cell Membrane; Cell Transformation, Neoplastic; Cells, Cultured; Cytoskeleton; Liver; Liver Neoplasms; Male; Methotrexate; Microtubules; Orosomucoid; Rats; Receptors, Cell Surface; Tetrahydrofolates