Nrf2 Expression Is Regulated by Epigenetic Mechanisms in Prostate Cancer of TRAMP Mice

Nuclear factor-erythroid 2 p45-related factor 2 (Nrf2) is a transcription factor which regulates the expression of many cytoprotective genes. In the present study, we found that the expression of Nrf2 was suppressed in prostate tumor of the Transgenic Adenocarcinoma of Mouse Prostate (TRAMP) mice. Similarly, the expression of Nrf2 and the induction of NQO1 were also substantially suppressed in tumorigenic TRAMP C1 cells but not in non-tumorigenic TRAMP C3 cells. Examination of the promoter region of the mouse Nrf2 gene identified a CpG island, which was methylated at specific CpG sites in prostate TRAMP tumor and in TRAMP C1 cells but not in normal prostate or TRAMP C3 cells, as shown by bisulfite genomic sequencing. Reporter assays indicated that methylation of these CpG sites dramatically inhibited the transcriptional activity of the Nrf2 promoter. Chromatin immunopreceipitation (ChIP) assays revealed increased binding of the methyl-CpG-binding protein 2 (MBD2) and trimethyl-histone H3 (Lys9) proteins to these CpG sites in the TRAMP C1 cells as compared to TRAMP C3 cells. In contrast, the binding of RNA Pol II and acetylated histone H3 to the Nrf2 promoter was decreased. Furthermore, treatment of TRAMP C1 cells with DNA methyltransferase (DNMT) inhibitor 5-aza-2′-deoxycytidine (5-aza) and histone deacetylase (HDAC) inhibitor trichostatin A (TSA) restored the expression of Nrf2 as well as the induction of NQO1 in TRAMP C1 cells. Taken together, these results indicate that the expression of Nrf2 is suppressed epigenetically by promoter methylation associated with MBD2 and histone modifications in the prostate tumor of TRAMP mice. Our present findings reveal a novel mechanism by which Nrf2 expression is suppressed in TRAMP prostate tumor, shed new light on the role of Nrf2 in carcinogenesis and provide potential new directions for the detection and prevention of prostate cancer.

[1]  B. Foster,et al.  Expression level and DNA methylation status of glutathione‐S‐transferase genes in normal murine prostate and TRAMP tumors , 2009, The Prostate.

[2]  Carmela Conte,et al.  Oxidative stress-related aging: A role for prostate cancer? , 2009, Biochimica et biophysica acta.

[3]  S. Nair,et al.  γ‐Tocopherol‐enriched mixed tocopherol diet inhibits prostate carcinogenesis in TRAMP mice , 2009, International journal of cancer.

[4]  A. Kong,et al.  Molecular mechanisms of Nrf2‐mediated antioxidant response , 2009, Molecular carcinogenesis.

[5]  T. Tammela,et al.  Clusterin is epigenetically regulated in prostate cancer , 2008, International journal of cancer.

[6]  A. Kong,et al.  Dietary Cancer Chemopreventive Agents – Targeting Inflammation and Nrf2 Signaling Pathway , 2008, Planta medica.

[7]  N. Kotrikadze,et al.  Activity and content of antioxidant enzymes in prostate tumors. , 2008, Experimental oncology.

[8]  Rui Wang,et al.  Hypermethylation of the Keap1 gene in human lung cancer cell lines and lung cancer tissues. , 2008, Biochemical and biophysical research communications.

[9]  A. Kong,et al.  Increased Susceptibility of Nrf2 Knockout Mice to Colitis-Associated Colorectal Cancer , 2008, Cancer Prevention Research.

[10]  M. T. Moser,et al.  Stage-Specific Alterations of DNA Methyltransferase Expression, DNA Hypermethylation, and DNA Hypomethylation during Prostate Cancer Progression in the Transgenic Adenocarcinoma of Mouse Prostate Model , 2008, Molecular Cancer Research.

[11]  M. Day,et al.  The role of Nrf2 in increased reactive oxygen species and DNA damage in prostate tumorigenesis , 2008, Oncogene.

[12]  M. T. Moser,et al.  Phenotype-specific CpG island methylation events in a murine model of prostate cancer. , 2008, Cancer research.

[13]  F. Ciardiello,et al.  Chronic inflammation and oxidative stress in human carcinogenesis , 2007, International journal of cancer.

[14]  O. Yossepowitch,et al.  Advanced but not localized prostate cancer is associated with increased oxidative stress. , 2007, The Journal of urology.

[15]  D. Bostwick,et al.  Glutathione S-transferase: differential expression of alpha, mu, and pi isoenzymes in benign prostate, prostatic intraepithelial neoplasia, and prostatic adenocarcinoma. , 2007, Human pathology.

[16]  A. Kong,et al.  Targeting carcinogen metabolism by dietary cancer preventive compounds. , 2007, Current cancer drug targets.

[17]  A. D. De Marzo,et al.  Abnormal DNA methylation, epigenetics, and prostate cancer. , 2007, Frontiers in bioscience : a journal and virtual library.

[18]  R. Kuefer,et al.  5-Aza-2′-Deoxycytidine Delays Androgen-Independent Disease and Improves Survival in the Transgenic Adenocarcinoma of the Mouse Prostate Mouse Model of Prostate Cancer , 2007, Clinical Cancer Research.

[19]  R. Henrique,et al.  Epigenetic Markers for Molecular Detection of Prostate Cancer , 2007, Disease markers.

[20]  D. Bostwick,et al.  Glutathione S-transferase: differential expression of alpha, mu, and pi isoenzymes in benign prostate, prostatic intraepithelial neoplasia, and prostatic adenocarcinoma. , 2007, Human pathology.

[21]  A. Kong,et al.  Nrf2-deficient mice have an increased susceptibility to dextran sulfate sodium-induced colitis. , 2006, Cancer research.

[22]  M. T. Moser,et al.  DNA methylation pathway alterations in an autochthonous murine model of prostate cancer. , 2006, Cancer research.

[23]  István Simon,et al.  The BiSearch web server , 2006, BMC Bioinformatics.

[24]  A. Conney,et al.  Inhibition of 7,12-dimethylbenz(a)anthracene-induced skin tumorigenesis in C57BL/6 mice by sulforaphane is mediated by nuclear factor E2-related factor 2. , 2006, Cancer research.

[25]  J. S. Rao,et al.  CpG island promoter methylation and silencing of 14-3-3σ gene expression in LNCaP and Tramp-C1 prostate cancer cell lines is associated with methyl-CpG-binding protein MBD2 , 2006, Oncogene.

[26]  W. Schulz,et al.  Epigenetics of prostate cancer: beyond DNA methylation , 2006, Journal of cellular and molecular medicine.

[27]  Stephanie Daignault,et al.  Inhibition of DNA methyltransferase activity prevents tumorigenesis in a mouse model of prostate cancer. , 2006, Cancer research.

[28]  A. Bird,et al.  Role of MBD2 in gene regulation and tumorigenesis. , 2005, Biochemical Society transactions.

[29]  A. Kong,et al.  Dietary cancer-chemopreventive compounds: from signaling and gene expression to pharmacological effects. , 2005, Trends in pharmacological sciences.

[30]  Gerald Batist,et al.  Transcriptional Regulation of NF-E2 p45-related Factor (NRF2) Expression by the Aryl Hydrocarbon Receptor-Xenobiotic Response Element Signaling Pathway , 2005, Journal of Biological Chemistry.

[31]  M. Day,et al.  Regulation of DNA methyltransferase 1 by the pRb/E2F1 pathway. , 2005, Cancer research.

[32]  A. D. De Marzo,et al.  GSTP1 CpG island hypermethylation as a molecular biomarker for prostate cancer , 2004, Journal of cellular biochemistry.

[33]  J. Hicks,et al.  Hypermethylation of the human glutathione S-transferase-pi gene (GSTP1) CpG island is present in a subset of proliferative inflammatory atrophy lesions but not in normal or hyperplastic epithelium of the prostate: a detailed study using laser-capture microdissection. , 2003, The American journal of pathology.

[34]  W. Nelson,et al.  Methyl-CpG-binding domain protein-2 mediates transcriptional repression associated with hypermethylated GSTP1 CpG islands in MCF-7 breast cancer cells. , 2003, Cancer research.

[35]  J. Christman,et al.  5-Azacytidine and 5-aza-2′-deoxycytidine as inhibitors of DNA methylation: mechanistic studies and their implications for cancer therapy , 2002, Oncogene.

[36]  Ken Itoh,et al.  Enhanced Expression of the Transcription Factor Nrf2 by Cancer Chemopreventive Agents: Role of Antioxidant Response Element-Like Sequences in the nrf2 Promoter , 2002, Molecular and Cellular Biology.

[37]  M. Kwak,et al.  Role of phase 2 enzyme induction in chemoprotection by dithiolethiones. , 2001, Mutation research.

[38]  H. Hauser,et al.  The NF-κB Repressing Factor Is Involved in Basal Repression and Interleukin (IL)-1-induced Activation of IL-8 Transcription by Binding to a Conserved NF-κB-flanking Sequence Element* , 2001, The Journal of Biological Chemistry.

[39]  D. Bostwick,et al.  Antioxidant enzyme expression and reactive oxygen species damage in prostatic intraepithelial neoplasia and cancer , 2000, Cancer.

[40]  B. Foster,et al.  Characterization of prostatic epithelial cell lines derived from transgenic adenocarcinoma of the mouse prostate (TRAMP) model. , 1997, Cancer research.

[41]  Y. Kan,et al.  NRF2, a member of the NFE2 family of transcription factors, is not essential for murine erythropoiesis, growth, and development. , 1996, Proceedings of the National Academy of Sciences of the United States of America.