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Type: Journal article
Title: GSTP1 DNA methylation and expression status is indicative of 5-aza-2'-deoxycytidine efficacy in human prostate cancer cells
Author: Chiam, K.
Centenera, M.
Butler, L.
Tilley, W.
Bianco-Miotto, T.
Citation: PLoS One, 2011; 6(9):e25634-1-e25634-11
Publisher: Public Library of Science
Issue Date: 2011
ISSN: 1932-6203
Statement of
Karen Chiam, Margaret M. Centenera, Lisa M. Butler, Wayne D. Tilley, Tina Bianco-Miotto
Abstract: DNA methylation plays an important role in carcinogenesis and the reversibility of this epigenetic modification makes it a potential therapeutic target. To date, DNA methyltransferase inhibitors (DNMTi) have not demonstrated clinical efficacy in prostate cancer, with one of the major obstacles being the inability to monitor drug activity during the trial. Given the high frequency and specificity of GSTP1 DNA methylation in prostate cancer, we investigated whether GSTP1 is a useful marker of DNMTi treatment efficacy. LNCaP prostate cancer cells were treated with 5-aza-29-deoxycytidine (5-aza-CdR) either with a single high dose (5–20 mM), every alternate day (0.1–10 mM) or daily (0.005–2.5 mM). A daily treatment regimen with 5-aza-CdR was optimal, with significant suppression of cell proliferation achieved with doses of 0.05 mM or greater (p,0.0001) and induction of cell death from 0.5 mM (p,0.0001). In contrast, treatment with a single high dose of 20 mM 5-aza-CdR inhibited cell proliferation but was not able to induce cell death. Demethylation of GSTP1 was observed with doses of 5-aza-CdR that induced significant suppression of cell proliferation ($0.05 mM). Re-expression of the GSTP1 protein was observed only at doses of 5-aza-CdR ($0.5 mM) associated with induction of cell death. Treatment of LNCaP cells with a more stable DNMTi, Zebularine required at least a 100-fold higher dose ($50 mM) to inhibit proliferation and was less potent in inducing cell death, which corresponded to a lack of GSTP1 protein re-expression. We have shown that GSTP1 DNA methylation and protein expression status is correlated with DNMTi treatment response in prostate cancer cells. Since GSTP1 is methylated in nearly all prostate cancers, our results warrant its testing as a marker of epigenetic therapy response in future clinical trials. We conclude that the DNA methylation and protein expression status of GSTP1 are good indicators of DNMTi efficacy.
Keywords: Cell Line, Tumor
Prostatic Neoplasms
Prostate-Specific Antigen
Enzyme Inhibitors
Cell Death
Cell Proliferation
Cell Survival
DNA Methylation
Gene Expression Regulation, Neoplastic
Gene Silencing
Dose-Response Relationship, Drug
Time Factors
Glutathione S-Transferase pi
Promoter Regions, Genetic
Drug Discovery
Biomarkers, Tumor
Rights: © 2011 Chiam et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
DOI: 10.1371/journal.pone.0025634
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