title: Isothiocyanate exposure, glutathione S-transferase polymorphisms, and colorectal cancer risk.
abstract: BACKGROUND
  Isothiocyanates, compounds found primarily in cruciferous vegetables, have been shown in laboratory studies to possess anticarcinogenic activity. Glutathione S-transferases (GSTs) are involved in the metabolism and elimination of isothiocyanates; thus, genetic variations in these enzymes may affect in vivo bioavailability and the activity of isothiocyanates.
  
  
  OBJECTIVE
  The objective was to prospectively evaluate the association between urinary isothiocyanate concentrations and colorectal cancer risk as well as the potential modifying effect of GST genotypes on the association.
  
  
  METHODS
  A nested case-control study of 322 cases and 1251 controls identified from the Shanghai Women's Health Study was conducted.
  
  
  RESULTS
  Urinary isothiocyanate concentrations were inversely associated with colorectal cancer risk; the inverse association was statistically significant or nearly significant in the GSTM1-null (P for trend = 0.04) and the GSTT1-null (P for trend = 0.07) genotype groups. The strongest inverse association was found among individuals with both the GSTM1-null and the GSTT1-null genotypes, with an adjusted odds ratio of 0.51 (95% CI: 0.27, 0.95), in a comparison of the highest with the lowest tertile of urinary isothiocyanates. No apparent associations between isothiocyanate concentration and colorectal cancer risk were found among individuals who carried either the GSTM1 or GSTT1 gene (P for interaction < 0.05).
  
  
  CONCLUSIONS
  This study suggests that isothiocyanate exposure may reduce the risk of colorectal cancer, and this protective effect may be modified by the GSTM1 and GSTT1 genes.
authors.affiliation: Department of Medicine, Vanderbilt University School of Medicine, Nashville, TN, USA. gong.yang@vanderbilt.edu
authors.forename: Gong
authors.initials: G
authors.lastname: Yang
authors.forename: Yu-Tang
authors.initials: YT
authors.lastname: Gao
authors.forename: Xiao-Ou
authors.initials: XO
authors.lastname: Shu
authors.forename: Qiuyin
authors.initials: Q
authors.lastname: Cai
authors.forename: Guo-Liang
authors.initials: GL
authors.lastname: Li
authors.forename: Hong-Lan
authors.initials: HL
authors.lastname: Li
authors.forename: Bu-Tian
authors.initials: BT
authors.lastname: Ji
authors.forename: Nathaniel
authors.initials: N
authors.lastname: Rothman
authors.forename: Marcin
authors.initials: M
authors.lastname: Dyba
authors.forename: Yong-Bing
authors.initials: YB
authors.lastname: Xiang
authors.forename: Fung-Lung
authors.initials: FL
authors.lastname: Chung
authors.forename: Wong-Ho
authors.initials: WH
authors.lastname: Chow
authors.forename: Wei
authors.initials: W
authors.lastname: Zheng
mesh_terms: D000368:Aged; D001682:Biological Availability; D019607:Brassicaceae / Q000737:chemistry*; D016022:Case-Control Studies; D002681:China; D015179:Colorectal Neoplasms / Q000235:genetics* / Q000652:urine; D004032:Diet; D005260:Female; D005982:Glutathione Transferase / Q000235:genetics*; D006801:Humans; D017879:Isothiocyanates / Q000652:urine*; D008875:Middle Aged; D016017:Odds Ratio; D011110:Polymorphism, Genetic; D012307:Risk Factors; D014675:Vegetables / Q000737:chemistry
chemical_list: D017879:Isothiocyanates; C037152:isothiocyanic acid; D005982:Glutathione Transferase