GSTP1 and prostate cancer: In addition, a GSTP1 methylation assay based on a hypermethylated CpG island in the promoter of GSTP1 and frequently reported in tumor tissues from prostate cancer patients is under clinical test to improve the detection sensitivity, specificity, and accuracy of early prostate cancer diagnosis (Martignano et al., 2016; Markou et al., 2017).