title: Blood leukocyte Alu and LINE-1 methylation and gastric cancer risk in the Shanghai Women's Health Study.
abstract: BACKGROUND
  Recent data suggest a link between blood leukocyte DNA methylation, and cancer risk. However, reports on DNA methylation from a prospective study are unavailable for gastric cancer.
  
  
  METHODS
  We explored the association between methylation in pre-diagnostic blood leukocyte DNA and gastric cancer risk in a case-control study nested in the prospective Shanghai Women's Health Study cohort. Incident gastric cancer cases (n=192) and matched controls (n=384) were included in the study. Methylation of Alu and long interspersed nucleotide elements (LINE)-1 were evaluated using bisulphite pyrosequencing. Odds ratios (ORs) and 95% confidence intervals (CI) were calculated from logistic regression adjusting for potential confounders.
  
  
  RESULTS
  Alu methylation was inversely associated with gastric cancer risk, mainly among cases diagnosed one or more years after blood collection. After excluding cases diagnosed during the first year of follow-up, the ORs for the third, second, and first quartiles of Alu methylation compared with the highest quartile were 2.43 (1.43-4.13), 1.47(0.85-2.57), and 2.22 (1.28-3.84), respectively. This association appeared to be modified by dietary intake, particularly isoflavone. In contrast, LINE-1 methylation levels were not associated with gastric cancer risk.
  
  
  CONCLUSIONS
  Evidence from this prospective study is consistent with the hypothesis that DNA hypomethylation in blood leukocytes may be related to cancer risk, including risk of gastric cancer.
authors.affiliation: Genetic Epidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-7236, USA. gaoying@mail.nih.gov
authors.forename: Y
authors.initials: Y
authors.lastname: Gao
authors.forename: A
authors.initials: A
authors.lastname: Baccarelli
authors.forename: X O
authors.initials: XO
authors.lastname: Shu
authors.forename: B-T
authors.initials: BT
authors.lastname: Ji
authors.forename: K
authors.initials: K
authors.lastname: Yu
authors.forename: L
authors.initials: L
authors.lastname: Tarantini
authors.forename: G
authors.initials: G
authors.lastname: Yang
authors.forename: H-L
authors.initials: HL
authors.lastname: Li
authors.forename: L
authors.initials: L
authors.lastname: Hou
authors.forename: N
authors.initials: N
authors.lastname: Rothman
authors.forename: W
authors.initials: W
authors.lastname: Zheng
authors.forename: Y-T
authors.initials: YT
authors.lastname: Gao
authors.forename: W-H
authors.initials: WH
authors.lastname: Chow
mesh_terms: D000328:Adult; D000368:Aged; D020087:Alu Elements / Q000235:genetics; D016022:Case-Control Studies; D002681:China / Q000453:epidemiology; D019175:DNA Methylation; D004273:DNA, Neoplasm / Q000032:analysis / Q000378:metabolism; D005260:Female; D006293:Health Promotion; D006801:Humans; D007962:Leukocytes / Q000378:metabolism*; D020084:Long Interspersed Nucleotide Elements / Q000235:genetics; D008875:Middle Aged; D011446:Prospective Studies; D012042:Registries; D012307:Risk Factors; D013274:Stomach Neoplasms / Q000097:blood / Q000453:epidemiology*; D016387:Women's Health
chemical_list: D004273:DNA, Neoplasm