Association of NAT2, GSTT1 and GSTM1 gene polymorphism and influence of oxidative stress on prostate cancer risk in Bangladeshi population

Abstract

Prostate cancer (PCa) is the second leading cause of cancer-related mortality in men. Prostate epithelial cell express phage II metabolizing enzymes, and recent molecular epidemiological studies have analyzed the relationship between N acetyltransferase and Glutathione S transferase gene polymorphism in the etiology of prostate cancer. It has been reported that NAT2 slow acetylators may be at increased risk of prostate cancer, due to their slower inactivation of environmental arylamines carcinogens. A systemic review and meta-analysis of GSTT1 and GSTM1 gene polymorphisms and prostate cancer risk in Asians showed that GSTT1 null genotype and GSTM1 null genotypes were significantly associated with prostate cancer risk. Oxidative stress has long been implicated in cancer development and progression. MDA is the product of lipid peroxidation, and erythrocyte reduced glutathione (GSH) is the major part of the antioxidant defense mechanism. Disturbances in GSH homeostasis are involved in the etiology and progression of many human diseases, including prostate cancer. Zinc is an element with biological functions as catalysts in various enzymatic reactions. Many studies around the world showed serum zinc has an association with prostate cancer. This study was undertaken to evaluate NAT2, GSTT1 and GSTM1 gene polymorphism and the influence of oxidative stress on prostate cancer risk in the Bangladeshi population. This casecontrol study included 207 histopathologically confirmed cases of prostate cancer that had not undergone any chemotherapy or radiotherapy and 200 age-matched healthy controls with the same geographical areas and ethnicities. After taking informed written consent, preset questioners were filled up, and about 6 ml of venous blood were collected with all ascetic precaution from each study subject. 3 ml blood was collected in an EDTA containing vial and processed for DNA extraction for NAT2, GSTT1, and GSTM1 gene analysis by PCR and erythrocyte reduced glutathione estimation. Serum was separated from the remaining 03 ml blood (contained in clot activator test tube) for biochemical analysis of serum PSA, MDA, GST, and Zinc. All data were plotted in SPSS version 23, and different statistical analyses were done. In this study, the mean age of cases was 67.3±8.3, and among control, it was 62.2±6.8 years. Study of genotype distribution and allele frequency of NAT2 polymorphism in study subjects found that prostate cancer cases had higher frequencies of mutant NAT2*5A (9.7% Vs. 5.5%), NAT2*6A (9.2% Vs. 5.0%) and NAT2*7A (5.3% Vs. 1.5%), in comparison to control. 19.8% of prostate cancer patients had slow genotypes for NAT2, and 80.2% had fast/rapid acetylator genotype, odds ratio (OR) (95% CI) was 1.90 (1.11-3.32), and results were statistically significant. NAT2 slow acetylator genotypes had a significantly higher risk for the development of moderate to high-grade tumors (Gleason score≥7) (OR=3.91, 95% CI, (2.11-7.15), p<0.001). 30% of a prostate cancer patient had null genotypes for GSTT1, and 37.7 % had null genotypes for GSTM1. The frequency of GSTT1 null genotype was slightly higher in prostate cancer cases than control with an OR of 1.45, but it was not statistically significant. On the other hand, the frequency of GSTM1 null genotype was significantly higher, with an OR of 1.71 in prostate cancer cases than control. Significantly higher risks for the development of high-grade tumors were also found for both GSTT1 and GSTM1 null genotypes. The combined genotype study of GSTT1 (null) / GSTM1 (null) showed a highly significant association with prostate cancer risk, and the risk increased 5.75-fold, compared to normal genotype for GSTT1 and GSTM1. However, the risk increased 5.54-fold for NAT2 (rapid) / GSTT1 (null) / GSTM1 (null) combination genotypes and risk increased 9.64-fold for NAT2 (slow) / GSTT1 (null) / GSTM1 (null) combination genotypes. Significantly higher risks for the development of high-grade tumors were also found for both GSTT1 and GSTM1 null genotypes. Oxidative stress marker malondialdehyde was significantly increased in prostate cancer patients than control. On the other hand, antioxidant erythrocyte reduced glutathione, and serum zinc level was significantly reduced in prostate cancer cases than control. In conclusion, significantly higher frequencies of mutant and heterozygote NAT2*6A and NAT2*7A/B genotypes were found in prostate cancer patients of the Bangladeshi population. There was a significant association of NAT2 slow genotypes and GSTM1 null genotypes with prostate cancer in the Bangladeshi population. Individuals with NAT2 slow genotype, GSTT1 null genotype, and GSTM1 null genotype along with positive smoking history/ positive family history of cancer / increased oxidative stress had increased risk for the development of prostate cancer. Presence of combined genotypes GSTT1 (null) / GSTM1 (null) or NAT2 (rapid) / GSTT1 (null) / GSTM1 (null) or NAT2 (slow) / GSTT1 (null) / GSTM1 (null) showed highly significant association with prostate cancer risk.