GSTP1 (glutathione-S-transferase, pi 1), also called GST3/DFN7, is a family of enzymes that play an important role in detoxification by catalyzing the conjugation of many hydrophobic and electrophilic compounds with reduced glutathione.GSTP1 act like a tumor suppressor gene, which when inactivated leads to tumor growth, and the -class glutathione S-transferase is commonly inactivated by somatic CpGisland hypermethylation in cancers of the prostate, liver, and breast.Methylation of regulatory sequences at the GSTP1 gene locus is found in the vast majority (>90%) of prostate carcinomas and is associated with transcriptional down-regulation.