title: Folate levels in mucosal tissue but not methylenetetrahydrofolate reductase polymorphisms are associated with gastric carcinogenesis.
abstract: OBJECTIVE
  To evaluate whether folate levels in mucosal tissue and some common methylenetetrahydrofolate reductase (MTHFR) variants are associated with the risk of gastric cancer through DNA methylation.
  
  
  METHODS
  Real-time PCR was used to study the expression of tumor related genes in 76 mucosal tissue samples from 38 patients with gastric cancer. Samples from the gastroscopic biopsy tissues of 34 patients with chronic superficial gastritis (CSG) were used as controls. Folate concentrations in these tissues were detected by the FOL ACS:180 automated chemiluminescence system. MTHFR polymorphisms were analyzed by PCR-RFLP, and the promoter methylation of tumor-related genes was determined by methylation-specific PCR (MSP).
  
  
  RESULTS
  Folate concentrations were significantly higher in CSG than in cancerous tissues. Decreased expression and methylation of c-myc accompanied higher folate concentrations. Promoter hypermethylation and loss of p16(INK4A) in samples with MTHFR 677CC were more frequent than in samples with the 677TT or 677CT genotype. And the promoter hypermethylation and loss of p21(WAF1) in samples with MTHFR 677CT were more frequent than when 677CC or 677TT was present. The 677CT genotype showed a non-significant higher risk for gastric cancer as compared with the 677CC genotype.
  
  
  CONCLUSIONS
  Lower folate levels in gastric mucosal tissue may confer a higher risk of gastric carcinogenesis through hypomethylation and overexpression of c-myc.
authors.affiliation: Shanghai Institute of Digestive Disease, Shanghai Jiao-Tong University School of Medicine, Renji Hospital, Shanghai 200001, China.
authors.forename: Yu-Rong
authors.initials: YR
authors.lastname: Weng
authors.forename: Dan-Feng
authors.initials: DF
authors.lastname: Sun
authors.forename: Jing-Yuan
authors.initials: JY
authors.lastname: Fang
authors.forename: Wei-Qi
authors.initials: WQ
authors.lastname: Gu
authors.forename: Hong-Yin
authors.initials: HY
authors.lastname: Zhu
mesh_terms: D005492:Folic Acid / Q000378:metabolism*; D005753:Gastric Mucosa / Q000378:metabolism; D005838:Genotype; D006801:Humans; D042965:Methylenetetrahydrofolate Reductase (NADPH2) / Q000235:genetics*; D011110:Polymorphism, Genetic; D012307:Risk Factors; D013274:Stomach Neoplasms / Q000453:epidemiology / Q000235:genetics* / Q000378:metabolism*
chemical_list: D005492:Folic Acid; D042965:Methylenetetrahydrofolate Reductase (NADPH2)