GSTP1 and benign prostatic hyperplasia: The most promising methylation biomarker identified to date is glutathione-S-transferase pi (GSTP1), detected in >90% of prostate tumours, >70% of HGPIN and at significantly lower frequencies and quantitatively much lower levels in normal prostate and benign prostatic hyperplasia (BPH) (Nakayama et al, 2003; Jeronimo et al, 2004).