Exploring the Role of Mitochondrial Sirtuin 3 Gene in Gastric Cancer Risk Based on SNP Analysis and LORD-Q Assay.

Mitochondrial sirtuin 3 (SIRT3) is a gene involved in key functions like acetylation, DNA repair, stress response, and tumorigenesis. Several studies have been published that showed the role of SIRT3 in various cancers. Still, few studies have been reported on the genetic and expression variation of the SIRT3 gene in gastric carcinogenesis. This study was designed to explore the involvement of the SIRT3 gene in gastric cancer. In this study, we used two study cohorts, cohort 1 contained 510 gastric cancer (GC) patients and an equal number of age and gender-matched controls. Cohort 2 included 220 GC tissue samples along with adjacent control tissues. Tetra Arms PCR was used to measure the frequency of three selected SNPs of the SIRT3 gene (rs28365927, rs11246029, and rs3817629) in cohort 1. Quantitative PCR and immunohistochemistry were performed to analyze the SIRT3 expression variation in cohort 2 GC patients. The superoxide dismutase (SOD), and 8-hydroxydeoxyguanosine (8-OHdG) levels were measured using ELISA, and DNA damage was measured using the LORD-Q assay. Statistical analysis showed the significant increased frequency of mutant allele of selected SNPs (rs28365927 (p < 0.0001); rs11246029 (p < 0.0001); and rs3817629 (p < 0.0001) in GC patients compared to controls. Expression analysis results showed significant downregulation of the SIRT3 gene at mRNA level (P < 0.001) and protein level (P < 0.001) in gastric tumor section vs control tissues. Multivariant Cox regression analysis showed that downregulated SIRT3 expression (p < 0.000001), H. pylori status (p < 0.0001), T-stage (p < 0.008), and N-stage (p < 0.001) act as prognostic markers in GC patients. ROC curve analysis showed the 90% and 100% specificity of the SIRT3 gene as a diagnostic marker in GC at the mRNA level and protein level, respectively. Significant increased oxidative stress (antioxidant enzyme level p < 0.0001; 8-OHdG level p < 0.0001) and lesion frequency/10 kb (p < 0.03) were indicated in the gastric tumor tissue sections vs controls. The result showed the tumor suppressor role of the SIRT3 gene in GC and was found linked with the surge in oxidative stress and damage in GC patients.