NAD(P)H:quinone oxidoreductase 1 Pro187Ser polymorphism and the risk of lung cancer: A meta-analysis

Background: NAD(P) H: quinine oxidoreductase 1 (NQO1) is a two-electron reductase that catalyzes quinine to hydroquinone. Variant genotypes of NQO1 Pro187Ser may be related to low enzyme activity and thus are suggested as affecting the risk of lung cancer. Our purpose was to study the NQO1 Pro187Ser polymorphism and the risk of lung cancer. Methods: We conducted a PubMed search and a China National Knowledge Infrastructure search using "NAD(P)H quinine reductase 1","lung cancer", and "polymorphism" for articles published from January 1997 to March 2010. For each study, we calculated the crude odds ratios (OR) and 95% confidence intervals (CI) for lung cancer. Summary estimates for crude as well as adjusted OR were calculated with the statistical program STATA. Results: The summary OR for carrying one variant allele and the homozygous variant genotype was 1.04 (95% CI, 0.97-1.13). In the Asian population, the summary OR for carrying one variant genotype was 1.09 (95% CI, 0.95-1.25). Conclusions: Through our meta-analysis, we found that the Pro/Ser and Ser/Ser genotypes involving NQO1 were non-significantly associated with lung cancer. In the Asian population, the combined genotype was marginally associated with increased risk of lung cancer. When stratified on gender and smoking, the meta-analysis showed that there was no statistically significant difference between men and women, smokers and non-smokers, respectively.