title: GSTP1 DNA methylation and expression status is indicative of 5-aza-2'-deoxycytidine efficacy in human prostate cancer cells.
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-2'-deoxycytidine (5-aza-CdR) either with a single high dose (5-20 µM), every alternate day (0.1-10 µM) or daily (0.005-2.5 µM). A daily treatment regimen with 5-aza-CdR was optimal, with significant suppression of cell proliferation achieved with doses of 0.05 µM or greater (p<0.0001) and induction of cell death from 0.5 µM (p<0.0001). In contrast, treatment with a single high dose of 20 µM 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 µM). Re-expression of the GSTP1 protein was observed only at doses of 5-aza-CdR (≥ 0.5 µM) 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 µM) 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.
authors: Dame Roma Mitchell Cancer Research Laboratories, Discipline of Medicine, University of Adelaide, Hanson Institute, Adelaide, Australia.
authors: Karen
authors: K
authors: Chiam
authors: Margaret M
authors: MM
authors: Centenera
authors: Lisa M
authors: LM
authors: Butler
authors: Wayne D
authors: WD
authors: Tilley
authors: Tina
authors: T
authors: Bianco-Miotto
mesh_terms: D001374:Azacitidine / Q000009:adverse effects / Q000031:analogs & derivatives* / Q000494:pharmacology; D014408:Biomarkers, Tumor / Q000172:deficiency / Q000235:genetics; D016923:Cell Death / Q000187:drug effects; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D003562:Cytidine / Q000031:analogs & derivatives / Q000494:pharmacology; D019175:DNA Methylation / Q000187:drug effects*; D000077209:Decitabine; D004305:Dose-Response Relationship, Drug; D055808:Drug Discovery; D004791:Enzyme Inhibitors / Q000009:adverse effects / Q000494:pharmacology*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects*; D020868:Gene Silencing / Q000187:drug effects; D051549:Glutathione S-Transferase pi / Q000172:deficiency / Q000235:genetics*; D006801:Humans; D008297:Male; D011401:Promoter Regions, Genetic / Q000187:drug effects / Q000235:genetics; D017430:Prostate-Specific Antigen / Q000097:blood; D011471:Prostatic Neoplasms / Q000097:blood / Q000235:genetics / Q000473:pathology*; D013997:Time Factors
chemical_list: D014408:Biomarkers, Tumor; D004791:Enzyme Inhibitors; D003562:Cytidine; D000077209:Decitabine; C009131:pyrimidin-2-one beta-ribofuranoside; C496556:GSTP1 protein, human; D051549:Glutathione S-Transferase pi; D017430:Prostate-Specific Antigen; D001374:Azacitidine