CYP2E1 T7632A and 9-bp insertion polymorphisms and colorectal cancer risk: a meta-analysis based on 4,592 cases and 5,918 controls.

Previous studies suggest that genetic factors play important roles in the development of colorectal cancer. CYP2E1 T7632A and 9-bp insertion polymorphisms may influence the risk of colorectal cancer, but published results are conflicting. We therefore conducted a meta-analysis comprising 9 case-control studies with 4,592 cases and 5,918 controls. Odds ratios (ORs) with 95 % confidence interval (95 % CI) were used to assess the strength of the associations of CYP2E1 T7632A and 9-bp insertion polymorphisms with colorectal cancer. For CYP2E1 T7632A polymorphism, meta-analysis showed that there was no significant association between the CYP2E1 T7632A polymorphism and colorectal cancer risk under all contrast models (A vs. T: OR = 1.06, 95 % CI 0.88-1.29, P = 0.528; AA vs. TT: OR = 0.85, 95 % CI 0.61-1.19, P = 0.351; AA/TA vs. TT: OR = 1.08, 95 % CI 0.87-1.34, P = 0.484; and AA vs. TT/TA: OR = 0.87, 95 % CI 0.62-1.21, P = 0.395). For CYP2E1 96-bp insertion polymorphism, meta-analysis showed that there was a significant association between the CYP2E1 96-bp insertion polymorphism and colorectal cancer risk under the allele contrast model and the dominant contrast model (for the allele contrast model: OR = 1.20, 95 % CI 1.06-1.36, P = 0.005; for the dominant contrast model: OR = 1.25, 95 % CI 1.07-1.45, P = 0.005). Subgroup analysis by race suggested that there was an obvious association between the CYP2E1 96-bp insertion polymorphism and colorectal cancer risk in Asians under the codominant contrast model. In conclusion, our meta-analysis demonstrates that there is a significant association between the CYP2E1 96-bp insertion polymorphism and colorectal cancer risk, and CYP2E1 9-bp insertion polymorphism is a risk factor for developing colorectal cancer.