The effect of CYP1A1 polymorphisms on the risk of lung cancer: a global meta-analysis based on 71 case-control studies

The cytochrome P450 1A1 (CYP1A1) is a phase I enzyme involved in many oxidative reactions that has attracted considerable attention as a candidate gene for lung cancer susceptibility based on its function as a key factor required for bioactivation of carcinogenic polycyclic aromatic hydrocarbons and catechol oestrogen formation. In the past decade, the relationship between CYP1A1 and lung cancer has been reported in various ethnic groups; however, these studies have yielded contradictory results. To investigate this inconsistency, we performed a meta-analysis of 71 studies involving a total of 30 368 subjects for the MspI and Ile-Val polymorphism of the CYP1A1 gene to evaluate the effect of CYP1A1 on genetic susceptibility for lung cancer. In a combined analysis, the summary per-allele odds ratios for lung cancer of the MspI and Ile-Val polymorphism were 1.19 [95% confidence interval (CI): 1.11-1.28] and 1.20 (95% CI: 1.08-1.33), respectively. Significant results were also observed using dominant or recessive genetic model. In the subgroup analysis by ethnicity, significantly increased risks were found for the MspI and Ile-Val polymorphism among East Asians in almost all genetic models. However, only marginal significant associations were detected for the MspI polymorphism among Caucasians and other population, while no significant associations were observed for the Ile-Val polymorphism in Caucasians and other population. This meta-analysis demonstrated that the MspI and Ile-Val polymorphism of CYP1A1 is a risk factor associated with increased lung cancer susceptibility, but these associations vary in different ethnic populations.