Genetic Variant Arg399Gln G>A of XRCC1 DNA Repair Gene Enhanced Cancer Risk Among Indian Population: Evidence from Meta-analysis and Trial Sequence Analyses

Genetic Variant XRCC1 rs1799782 (C194T) and Risk of Cancer Susceptibility in Indian Population: A Meta-analysis of Case-Control Studies

X-ray repair cross-complementing group 1 (XRCC1) plays a key role in the base excision repair pathway, as a scaffold protein that brings together proteins of the DNA repair complex. Several studies have reported contradictory results for XRCC1 exon 6 C>T (rs1799782) gene polymorphism and cancer risk in Indian population has provided inconsistent results. Therefore, we have performed this meta-analysis to evaluate the relationship between XRCC1 exon 6 C>T gene polymorphism and risk of cancer by published studies. We searched PubMed and Google scholar web databases to cover all studies published on association between XRCC1 exon 6 C>T gene polymorphism and cancer risk. The meta-analysis was carried out and pooled odds ratios (ORs) and 95% confidence intervals (95% CIs) were used to appraise the strength of association. In order to derive a more precise estimation of the association, A total of 3197 confirmed cancer cases and 3819 controls were included from eligible seventeen case-controls studies. Results from overall pooled analysis demonstrated suggested that that variant allele (T vs. C: OR 1.301, 95% CI 1.003-1.688, p = 0.047) was associated with the risk of overall cancer. Other genetic models; heterozygous (TC vs. CC: OR 1.108, 95% CI 0.827-1.485, p = 0.491), homozygous (TT vs. CC: OR 1.479, 95% CI 0.877-2.493, p = 0.142), dominant (TT+TC vs. CC: OR 1.228, 95% CI 0.899-1.677, p = 0.196) and recessive (TT vs. TC+CC: OR 1.436, 95% CI 0.970-2.125, p = 0.071) did not reveal statistical association. Publication bias observation was also considered and none was detected during the analysis. The present meta-analysis suggested that the variant allele T of XRCC1 exon 6 gene polymorphism was associated with the risk of cancer. It is therefore pertinent to confirm this finding in a large sample size to divulge the mechanism of this polymorphism and cancer risk in Indian population.

Glutathione S-Transferase P1 313 (A > G) Ile105Val Polymorphism Contributes to Cancer Susceptibility in Indian Population: A Meta-analysis of 39 Case-Control Studies

GSTP1 involved in the metabolism of carcinogens and toxins, reduces damage of DNA and act as a suppressor of carcinogenesis. Many studies have reported that 313 A > G polymorphism is associated with different cancer in Indian population, but the results remain conflicting rather than conclusive. Therefore, we have performed meta-analysis to clarify the more precise association of GSPT1 313 A > G polymorphism with cancer risk in Indian population. We retrieved all relevant published literature from PubMed (Medline) and Google scholar web database and included those study only based on the established inclusion criteria. Pooled ORs and 95% CIs were used to appraise the strength of association. Publication bias and sensitivity analysis was also evaluated. A total of 6581 confirmed cancer cases and 8218 controls were included from eligible thirty nine case-controls studies. Pooled analysis suggested that the variant genotypes significantly increased the risk of cancer in allele (G vs. A: OR 1.266, 95% CI 1.129-1.418, p = 0.001), heterozygous (AG vs. AA: OR 1.191, 95% CI 1.047-1.355, p = 0.008), homozygous (GG vs. AA: OR 1.811, 95% CI 1.428-2.297, p = 0.001), dominant (GG + AG vs. AA: OR 1.276, 95% CI 1.110-1.466, p = 0.001) and recessive (GG vs. AG + AA: OR 1.638, 95% CI 1.340-2.002, p = 0.001) genetic models. The stability of these observations was confirmed by a sensitivity analysis. Begger's funnel plot and Egger's test did not reveal any publication bias. This meta-analysis suggests that the GSTP1 313 A > G polymorphism may contribute to genetic susceptibility to cancer in Indian population. However, larger studies and randomized clinical trial will be required to elucidate the biological and molecular mechanism of GSTP1 gene in cancer.