DNA Methylation of GSTP1 in Human Prostate Tissues: Pyrosequencing Analysis

Purpose: DNA methylation is an important epigenetic mechanism of gene regulation and plays essential roles in tumor initiation and progression. Differences in methylation patterns between neoplastic and normal cells can be used to detect the presence of cancer. The aim of the present study was to evaluate the usefulness of glutathione- S-transferase-Pi (GSTP1) hypermethylation in discriminating between normal and prostate cancer (PCa) cells and in predicting tumor characteristics by use of quantitative pyrosequencing analysis. Materials and Methods: A total of 100 human prostate tissues obtained from our institute were used in this study: 45 for benign prostatic hyperplasia (BPH) and 55 for PCa. The methylation level of GSTP1 was examined by a quantitative pyrosequencing analysis. The associations between GSTP1 methylation level and clinico-pathological parameter were also compared. Results: The level of GSTP1 methylation was significantly higher in PCa samples than in BPH samples (56.7 +/- 32.7% vs. 1.6 +/- 2.2%, p<0.001). The sensitivity and specificity of GSTP1 methylation status in discriminating between PCa and BPH reached 85.5% and 100%, respectively. Even after stratification by stage, Gleason score, and prostate-specific antigen (PSA) level, similar results were obtained. A positive correlation between GSTP1 methylation level and serum PSA level was observed (r=0.303, p=0.002). There were no associations between GSTP1 methylation level and age, Gleason score, and staging. Conclusions: Our study demonstrates that GSTP1 methylation is associated with the presence of PCa and PSA levels. This methylation marker is a potentially useful indicator for the detection and monitoring of PCa.