Expression deregulation of DNA repair pathway genes in gastric cancer

This study was designed to check correlation of mRNA and protein expression of BER pathway genes(XRCC1, OGG1) and a proliferation marker (Ki-67) in 100 gastric tissue samples and controls (adjacent uninvolved area). The expression was estimated using real time PCR and immunohistochemistry. Genomic instability was also calculated in the same study cohort using 8-OHdG assay, DNA fragmentation assay and comet assay. A significant downregulation of XRCC1 (p < 0.0001) and OGG1 (p < 0.0001) expression was observed in gastric cancer tumors vs controls. When analyzed with spearman correlation, significant positive correlation was observed between OGG1 vs XRCC1 (r = 0.319*, p < 0.02) and significant negative correlation was observed between OGG1 vs Ki-67 (r = -0.462**, p < 0.001) and XRCC1 vs Ki-67 (r = -0.589**, p < 0.001) in gastric cancer tumors. Significantly higher level of 8-OHdG, when compared to controls, was observed in gastric cancer tumors (p < 0.0001). DNA fragmentation assay and comet assay showed the formation of increased ladder patterns and comets in gastric cancer tumors when compared with controls These findings suggest that dysregulation of XRCC1, OGG1 combined with overexpression of Ki-67 may contribute to progression of gastric cancer and may help to sub-classify patients within diverse risk groups for therapeutic advantages.