Associations of CYP2E1 rs2031920 and rs3813867 polymorphisms with colorectal cancer risk: a systemic review and meta-analysis.

Cytochrome P450 2E1 (CYP2E1) is a natural enzyme involved in the metabolic activation of many carcinogens, and the functional polymorphisms in the CYP2E1 gene might have impacts on colorectal cancer risk. Many studies were published to assess the associations of CYP2E1 rs2031920 and rs3813867 polymorphisms with colorectal cancer risk, but no consistent findings were reported. A systemic review and meta-analysis of eligible studies was performed to comprehensively assess the associations above. Odds ratios (ORs) with 95 % confidence interval (95 % CIs) were used to assess the strength of the associations. Seventeen studies from 15 publications with 17,082 individuals were finally included into this meta-analysis. Meta-analysis of the 13 studies on CYP2E1 rs2031920 polymorphism showed that there was a significant association between CYP2E1 rs2031920 polymorphism and colorectal cancer risk under two genetic models (c2 versus c1: OR = 1.19, 95 % CI 1.03-1.37, P = 0.022; c2c2/c2c1 versus c1c1: OR = 1.16, 95 % CI 1.00-1.35, P = 0.046). Meta-analysis of those four case-control studies on CYP2E1 rs3813867 polymorphism showed that there was no significant association between CYP2E1 rs3813867 polymorphism and colorectal cancer risk under all contrast models (c2 versus c1: OR = 0.96, 95 % CI 0.80-1.16, P = 0.672; c2c2 versus c1c1: OR = 1.26, 95 % CI 0.43-3.67, P = 0.672; c2c2/c1c2 versus c1c1: OR = 0.95, 95 % CI 0.78-1.16, P = 0.114; and c2c2 versus c1c2/c1c1: OR = 1.17, 95 % CI 0.41-3.36, P = 0.775). Therefore, the findings from this meta-analysis suggest that CYP2E1 rs2031920 polymorphism is associated with colorectal cancer risk, but CYP2E1 rs3813867 polymorphism is not associated with colorectal cancer risk. In addition, more well-designed studies with large sample size are needed to provide a more precise evaluation on the associations above.