Even though Zebularine effectively reduced prostate cancer cell number, it was unable to induce significant cell death, possibly due to its weak demethylating activity and inability to reactivate silenced genes such as GSTP1. Although initial studies suggested that Zebularine may be a better DNMTi than 5-aza-CdR for clinical use, this and other studies suggest that Zebularine is not as effective as 5-aza-CdR as a demethylating agent [39], [57]. This evidence concerns the gene GSTP1 and Familial prostate cancer.