1. Expression level and DNA methylation status of glutathione-S-transferase genes in normal murine prostate and TRAMP tumors.
- Author
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Mavis CK, Morey Kinney SR, Foster BA, and Karpf AR
- Subjects
- Adenocarcinoma drug therapy, Adenocarcinoma pathology, Animals, Antimetabolites, Antineoplastic pharmacology, Azacitidine analogs & derivatives, Azacitidine pharmacology, Cell Line, Tumor, CpG Islands genetics, Decitabine, Drug Combinations, Gene Expression Regulation, Neoplastic physiology, Gene Silencing, Glutathione S-Transferase pi genetics, Glutathione S-Transferase pi metabolism, Hydroxamic Acids pharmacology, Male, Mice, Mice, Inbred C57BL, Mice, Transgenic, Neoplasm Metastasis genetics, Prostatic Neoplasms drug therapy, Prostatic Neoplasms pathology, RNA, Messenger metabolism, Adenocarcinoma genetics, DNA Methylation, Gene Expression Regulation, Enzymologic physiology, Glutathione Transferase genetics, Prostate enzymology, Prostatic Neoplasms genetics
- Abstract
Background: Glutathione-S-transferase (Gst) genes are downregulated in human prostate cancer, and GSTP1 silencing is mediated by promoter DNA hypermethylation in this malignancy. We examined Gst gene expression and Gst promoter DNA methylation in normal murine prostates and Transgenic Adenocarcinoma of Mouse Prostate (TRAMP) tumors., Methods: Primary and metastatic tumors were obtained from TRAMP mice, and normal prostates were obtained from strain-matched WT mice (n = 15/group). Quantitative real-time RT-PCR was used to measure GstA4, GstK1, GstM1, GstO1, and GstP1 mRNA expression, and Western blotting and immunohistochemical staining was used to measure GstM1 and GstP1 protein expression. MassARRAY Quantitative Methylation Analysis was used to measure DNA methylation of the 5' CpG islands of GstA4, GstK1, GstM1, GstO1, and GstP1. TRAMP-C2 cells were treated with the epigenetic remodeling drugs decitabine and trichostatin A (TSA) alone and in combination, and Gst gene expression was measured., Results: Of the genes analyzed, GstM1 and GstP1 were expressed at highest levels in normal prostate. All five Gst genes showed greatly reduced expression in primary tumors compared to normal prostate, but not in tumor metastases. Gst promoter methylation was unchanged in TRAMP tumors compared to normal prostate. Combined decitabine + TSA treatment significantly enhanced the expression of 4/5 Gst genes in TRAMP-C2 cells., Conclusions: Gst genes are extensively downregulated in primary but not metastatic TRAMP tumors. Promoter DNA hypermethylation does not appear to drive Gst gene repression in TRAMP primary tumors; however, pharmacological studies using TRAMP cells suggest the involvement of epigenetic mechanisms in Gst gene repression.
- Published
- 2009
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