GCPII modulates oxidative stress and prostate cancer susceptibility through changes in methylation of RASSF1, BNIP3, GSTP1 and Ec-SOD

Glutamate carboxypeptidase II (GCPII) haplotypes were found to influence susceptibility to prostate cancer. In the current study, we have elucidated the impact of these haplotypes on the expression of PSMA, BNIP3, Ec-SOD, GSTP1 and RASSF1 genes to understand the epigenetic basis of oxidative stress and prostate cancer risk. Expression analysis was carried out by RT-PCR. Bisulphite treated DNA was subjected to MS-PCR and COBRA for epigenetic studies. Plasma MDA and glutathione levels were measured. In prostate cancer, upregulation of BNIP3 (204.4 ± 23.77 vs. 143.9 ± 16.42 %, p = 0.03); and downregulation of Ec-SOD (105.8 ± 13.69 vs. 176.3 ± 21.1 %, p = 0.027) and RASSF1A (16.67 ± 16.0 vs. 90.8 ± 8.5 %, p = 0.0048) was observed. Hypomethylation of BNIP3 (31.25 ± 16.19 vs. 45.70 ± 2.42 %, p < 0.0001), hypermethylation of Ec-SOD (71.4 ± 6.75 vs. 10.0 ± 3.78 %, p < 0.0001) and RASSF1 (76.25 ± 12.53 vs. 30.0 ± 8.82 %, p = 0.0077) was observed in prostate cancer. The gene expression signature of PSMA, BNIP3, Ec-SOD, GSTP1, clearly demarcated cases and controls (AUC = 0.89 in the ROC curve). D191V variant of GCPII showed positive association with oxidative stress and inverse association with Ec-SOD expression. H475Y variant showed positive association with Ec-SOD expression and inverse association with oxidative stress. R190W variant was found to reduce oxidative stress by increasing glutathione levels. GCPII genetic variants contribute to increased oxidative stress and prostate cancer risk by modulating the CpG island methylation of Ec-SOD.