| Summary: | 碩士 === 輔仁大學 === 營養科學系 === 96 === The aims of the study were to investigate effects of genetic polymorphisms of one-carbon enzymes on one carbon metabolism, risk of hepatocellular carcinoma(HCC) , and DNA oxidative lesions. In the first part of this pilot study, 90 HCC cases and 90 age- and sex- paired healthy controls were recruited from Chi-Mei Medcal Center, Tianan, Taiwan. Real time PCR with designed primers and probes was used to determine the MTHFR (5,10-methylene- tetrahydrofolate reductase) C677T, MTHFR A1298C, MS (methionine synthase )A2756G, TSER (thymidylate synthase), TS3’UTR and hOGG1 C1245G genetics polymorphism. The genotypic and frequencies of the one-carbon metabolism genetics polymorphism and hOGG1 C1245G did not differ significantly between healthy controls and HCC patients. The serum folate concentration was significantly lower in the MTHFR 677TT and 1298CC genotypes compared with wild type homozygotes (P=0.04). The serum homocysteine concentration was significantly higher in the MTHFR 677TT genotype compared with 677CC genotype(P=0.04). After the adjustment of multiple factors, odds ratio of the HCC risk was 0.005(adjusted OR=0.005, 95% CI=0.001-0.54, P=0.03) , for subjects carrying MTHFR 677TT genotype as compared to those carrying 677CC genotype. In the second part ot the study, mitochondrial DNA (mtDNA) large deletion and copy number were quantified by real-time PCR among all subjects. The mtDNA large deletions were significantly lower in the 677CC genotype compared with 677CC genotype among HCC patients. When 25 HCC patients and 18 age- and sex-paired healthy control with MTHFR variants were selected for further analysis of mtDNA and nuclear DNA lesions, direct sequencing of the mtDNA D-loop region of the subjects revealed that lower rate of D310 mononucleotide repeat mutation was observed in HCC patients with MTHFR 677CT+677TT genotypes than 677CC variants (P=0.03). By use of real-time PCR with designed primers to detect the 8-OHdG lesions in the mtD-loop and p53 promoter region, the data showed that HCC patients with MTHFR 677TT genotype had significantly lower 8-OHdG lesions than healthy controls with same genotype (P=0.04). Subjects also had significantly lower 8-OHdG lesions at p53 promoter region in the 677TT genotype compared with 677CC genotype(P=0.04). The last part of the study was conducted using HCC cell lines with MTHFR polymorphisms: Hep 3B (677CC), HepG2 (677CT), and SK-Hep 1(677CC) to explore the interactions of folate status and MTHFR polymorphisms on DNA lesions. SK-Hep 1 cells with MTHFR 677TT genotype had significantly lower 8-OHdG lesions compared with Hep 3B (677CC) and HepG2 (677CT). Prolonged folate deficiency increased levels of mtDNA large deletion, mtDNA copy number, levels of 8-OHdG, mtD-loop region and p53 promoter region lesions in all three HCC cell lines. In summary, our data shows protective effects of the MTHFR 677TT on risk of HCC. Lower mtDNA large deletion, mtD-loop region mutation, and 8-OHdG lesions in the promoter region of p53 tumour suppressor gene observed in individuals with MTHFR 677TT genotype may partially, if not all, explain the protective mechanisms of this MTHFR polymorphisms to reduced risks of HCC.
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