title: Genetic polymorphism of glutathione S-transferase T1 and the risk of colorectal cancer: a meta-analysis.
abstract: BACKGROUND
  Studies investigating the association between genetic polymorphism of glutathione S-transferase T1 (GSTT1) and risk of colorectal cancer have reported conflicting results. In order to clarify the effect of GSTT1 polymorphism on the risk of developing colorectal cancer, we carried out a meta-analysis using published data to obtain more precise estimates of risk.
  
  
  METHODS
  Electronic searches of PubMed and EMBASE were conducted to select studies for this meta-analysis. Papers were included if they were observational studies investigating the association between GSTT1 polymorphism and colorectal cancer risk. The principal outcome measure was the odds ratio (OR) with 95% confidence interval (CI) for the risk of colorectal cancer associated with GSTT1 null genotype.
  
  
  RESULTS
  We identified 30 eligible studies, which included 7635 cases and 12,911 controls. The combined results based on all studies showed that there was a statistically significant link between GSTT1 null genotype and colorectal cancer risk (OR=1.20, 95% CI=1.03-1.40). In the analysis of ethnic groups, we observed distinct differences associated with GSTT1 null genotype, the pooled odds ratios for the GSTT1 polymorphism were 1.32 in Caucasians (95% CI=1.09-1.58) and 1.03 in Asians (95% CI=0.81-1.32). As far as concerned the interaction between GSTT1 genotype and colorectal cancer risk in relation to smoking history, there was no increase in risk for smokers or nonsmokers with the GSTT1 null genotype (smokers: OR=1.13, 95% CI=0.80-1.60, nonsmokers: OR=0.99, 95% CI=0.71-1.38). When stratifying by the location of colorectal cancer, we found that there was a statistically significant link in rectal cancer (OR=1.50, 95% CI=1.09-2.07), but not in colon cancer (OR=1.33, 95% CI=0.94-1.88). No associations could be detected between null GSTT1 polymorphism and age, sex, tumor stage and differentiation.
  
  
  CONCLUSIONS
  Our current study demonstrates that GSTT1 null genotype is associated with an increased risk of colorectal cancer, specifically, among Caucasians.
authors.affiliation: West China School of Medicine Sichuan University, Chengdu 610041, Sichuan Province, China.
authors.forename: Hongwei
authors.initials: H
authors.lastname: Wan
authors.forename: Yong
authors.initials: Y
authors.lastname: Zhou
authors.forename: Ping
authors.initials: P
authors.lastname: Yang
authors.forename: Bo
authors.initials: B
authors.lastname: Chen
authors.forename: Guiqing
authors.initials: G
authors.lastname: Jia
authors.forename: Xiaoting
authors.initials: X
authors.lastname: Wu
mesh_terms: D000368:Aged; D015179:Colorectal Neoplasms / Q000453:epidemiology / Q000235:genetics*; D005982:Glutathione Transferase / Q000235:genetics*; D006801:Humans; D008297:Male; D008875:Middle Aged; D011110:Polymorphism, Genetic; D012307:Risk Factors
chemical_list: C413545:glutathione S-transferase T1; D005982:Glutathione Transferase