GSTP1 expression and promoter methylation in epithelial ovarian carcinoma

Context: GSTP1 is a subgroup of glutathione-S-transferase family, which provides cellular protection against free radical and carcinogenic compounds due to its detoxifying function. Altered GSTP1 activity due to down regulation of enzyme activity and DNA methylation has been reported in many tumors, although data for ovarian cancer are few. In this study, we aimed at determining the expression of GSTP1 in relation to the methylation of the GSTP1 promoter in epithelial ovarian cancer (EOC). Materials and Methods: GSTP1 mRNA expression and GSTP1 enzyme concentration were assessed by quantitative reverse transcriptase polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay, respectively, in 88 EOCs, 14 low malignant potential (LMP) tumors, and 20 benign tumors. The promoter methylation of GSTP1 gene was evaluated by methylation-specific PCR. Results: Reduced GSTP1 mRNA expression was observed in 49% EOCs, 21.4% LMP, and 45% benign tumors. Significantly lower levels of plasma GSTP1 were observed in all tumor samples compared to normal. GSTP1 promoter methylation was detected in 10 (11.4%) EOCs and 1 (7.3%) LMP tumors. No methylation was observed in benign tumors and normal ovaries. Conclusions: Our results show that there is a significant down regulation of GSTP1 expression while hypermethylation of the GSTP1 gene promoter is not very frequent in EOC. Further studies are needed to study underlying mechanisms leading to decreased expression.