A systemic review of glutathione S-transferase P1 Ile105Val polymorphism and colorectal cancer risk

Objectives: To investigate the correlation between glutathione S-transferase P1 (GSTP1) Ile105Val polymorphism and colorectal cancer (CRC) risk. Methods: Studies were identified to investigate the association between GSTP1 Ile105Val polymorphism and CRC risk. Systematic computerized searches of the PubMed, Chinese National Knowledge Infrastructure, WANFANG and SinoMed were performed. Summary odds ratios (OR) and 95% confidence intervals (95% Cl) were used to measure GSTP1 Ile105Val polymorphisms and CRC risk. Results: A total of 23 retrospective studies were included in the meta-analysis. During all studies including 6,981 cases and 8,977 controls, sample sizes ranged from 146 to 2,144. Overall, the pooled results revealed that Ile105Val polymorphism was not associated with CRC risk and confused results were found in subgroup analyses. Further meta-analyses were conducted after excluding low-quality studies. GSTP1 Ile105Val is associated with increased risk of CRC limited in studies with matched control. There was no significant heterogeneity in all genetic comparisons, but heterogeneity existed in subgroup analyses of heterozygous and dominant comparisons. The meta-regression analyses indicated that matched controls were the significant factor influencing between-study heterogeneity in all possible influential factors including published year, ethnicity, source of control, sample size, Hardy-Weinberg equilibrium (HWE) in control and matched controls. Sensitivity analysis revealed the pooled ORs were not changed before and after removal of each single study in all genetic comparisons, indicating the robustness of the results. Conclusions: GSTP1 Ile105Val might be associated with increased risk of CRC. However, more high-quality case-control studies should be performed to confirm the authenticity of our conclusion.