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Basak D, Gregori L, Johora F, Deb S. Preclinical and Clinical Research Models of Prostate Cancer: A Brief Overview. LIFE (BASEL, SWITZERLAND) 2022; 12:life12101607. [PMID: 36295041 PMCID: PMC9605520 DOI: 10.3390/life12101607] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Revised: 09/29/2022] [Accepted: 09/30/2022] [Indexed: 11/11/2022]
Abstract
The incidence and mortality from prostate cancer (PCa) are on the rise which poses a major public health concern worldwide. In this narrative review, we have summarized the characteristics of major in vitro and in vivo PCa models including their utility in developing treatment strategies. Androgens, particularly, testosterone and dihydrotestosterone (DHT) activate the androgen receptor (AR) signaling pathway that facilitates the development and progression of castration resistant PCa. Several enzymes namely, CYP17A1, HSD17B, and SRD5A are essential to furnishing DHT from dehydroepiandrosterone in the classical pathway while DHT is formed from androstanediol in the backdoor pathway. The advancement in delineating the molecular heterogeneity of PCa has been possible through the development of several in vitro and in vivo research models. Generally, tissue culture models are advantageous to understand PCa biology and investigate the efficacy and toxicity of novel agents; nevertheless, animal models are indispensable to studying the PCa etiology and treatment since they can simulate the tumor microenvironment that plays a central role in initiation and progression of the disease. Moreover, the availability of several genetically engineered mouse models has made it possible to study the metastasis process. However, the conventional models are not devoid of limitations. For example, the lack of heterogeneity in tissue culture models and the variation of metastatic characteristics in xenograft models are obviously challenging. Additionally, due to the racial and ethnic disparities in PCa pathophysiology, a new model that can represent PCa encompassing different ethnicities is urgently needed. New models should continue to evolve to address the genetic and molecular complexities as well as to further elucidate the finer details of the steroidogenic pathway associated with PCa.
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Özturan D, Morova T, Lack NA. Androgen Receptor-Mediated Transcription in Prostate Cancer. Cells 2022; 11:cells11050898. [PMID: 35269520 PMCID: PMC8909478 DOI: 10.3390/cells11050898] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2022] [Revised: 02/25/2022] [Accepted: 03/01/2022] [Indexed: 11/16/2022] Open
Abstract
Androgen receptor (AR)-mediated transcription is critical in almost all stages of prostate cancer (PCa) growth and differentiation. This process involves a complex interplay of coregulatory proteins, chromatin remodeling complexes, and other transcription factors that work with AR at cis-regulatory enhancer regions to induce the spatiotemporal transcription of target genes. This enhancer-driven mechanism is remarkably dynamic and undergoes significant alterations during PCa progression. In this review, we discuss the AR mechanism of action in PCa with a focus on how cis-regulatory elements modulate gene expression. We explore emerging evidence of genetic variants that can impact AR regulatory regions and alter gene transcription in PCa. Finally, we highlight several outstanding questions and discuss potential mechanisms of this critical transcription factor.
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Affiliation(s)
- Doğancan Özturan
- School of Medicine, Koç University, Istanbul 34450, Turkey;
- Koç University Research Centre for Translational Medicine (KUTTAM), Koç University, Istanbul 34450, Turkey
| | - Tunç Morova
- Vancouver Prostate Centre, Department of Urologic Sciences, University of British Columbia, Vancouver, BC V6H 3Z6, Canada;
| | - Nathan A. Lack
- School of Medicine, Koç University, Istanbul 34450, Turkey;
- Koç University Research Centre for Translational Medicine (KUTTAM), Koç University, Istanbul 34450, Turkey
- Vancouver Prostate Centre, Department of Urologic Sciences, University of British Columbia, Vancouver, BC V6H 3Z6, Canada;
- Correspondence: ; Tel.: +1-604-875-4411 (ext. 6417)
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3
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PIM1 phosphorylation of the androgen receptor and 14-3-3 ζ regulates gene transcription in prostate cancer. Commun Biol 2021; 4:1221. [PMID: 34697370 PMCID: PMC8546101 DOI: 10.1038/s42003-021-02723-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Accepted: 09/21/2021] [Indexed: 11/19/2022] Open
Abstract
PIM1 is a serine/threonine kinase over-expressed in prostate cancer. We have previously shown that PIM1 phosphorylates the androgen receptor (AR), the primary therapeutic target in prostate cancer, at serine 213 (pS213), which alters expression of select AR target genes. Therefore, we sought to investigate the mechanism whereby PIM1 phosphorylation of AR alters its transcriptional activity. We previously identified the AR co-activator, 14-3-3 ζ, as an endogenous PIM1 substrate in LNCaP cells. Here, we show that PIM1 phosphorylation of AR and 14-3-3 ζ coordinates their interaction, and that they extensively occupy the same sites on chromatin in an AR-dependent manner. Their occupancy at a number of genes involved in cell migration and invasion results in a PIM1-dependent increase in the expression of these genes. We also use rapid immunoprecipitation and mass spectrometry of endogenous proteins on chromatin (RIME), to find that select AR co-regulators, such as hnRNPK and TRIM28, interact with both AR and 14-3-3 ζ in PIM1 over-expressing cells. We conclude that PIM1 phosphorylation of AR and 14-3-3 ζ coordinates their interaction, which in turn recruits additional co-regulatory proteins to alter AR transcriptional activity.
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4
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Ryan GE, Bohaczuk SC, Cassin J, Witham EA, Shojaei S, Ho EV, Thackray VG, Mellon PL. Androgen receptor positively regulates gonadotropin-releasing hormone receptor in pituitary gonadotropes. Mol Cell Endocrinol 2021; 530:111286. [PMID: 33872733 PMCID: PMC8177864 DOI: 10.1016/j.mce.2021.111286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/23/2020] [Revised: 03/29/2021] [Accepted: 04/13/2021] [Indexed: 11/30/2022]
Abstract
Within pituitary gonadotropes, the gonadotropin-releasing hormone receptor (GnRHR) receives hypothalamic input from GnRH neurons that is critical for reproduction. Previous studies have suggested that androgens may regulate GnRHR, although the mechanisms remain unknown. In this study, we demonstrated that androgens positively regulate Gnrhr mRNA in mice. We then investigated the effects of androgens and androgen receptor (AR) on Gnrhr promoter activity in immortalized mouse LβT2 cells, which represent mature gonadotropes. We found that AR positively regulates the Gnrhr proximal promoter, and that this effect requires a hormone response element (HRE) half site at -159/-153 relative to the transcription start site. We also identified nonconsensus, full-length HREs at -499/-484 and -159/-144, which are both positively regulated by androgens on a heterologous promoter. Furthermore, AR associates with the Gnrhr promoter in ChIP. Altogether, we report that GnRHR is positively regulated by androgens through recruitment of AR to the Gnrhr proximal promoter.
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Affiliation(s)
- Genevieve E Ryan
- Department of Obstetrics, Gynecology and Reproductive Sciences, Center for Reproductive Science and Medicine, University of California, San Diego, La Jolla, CA, 92093, USA.
| | - Stephanie C Bohaczuk
- Department of Obstetrics, Gynecology and Reproductive Sciences, Center for Reproductive Science and Medicine, University of California, San Diego, La Jolla, CA, 92093, USA.
| | - Jessica Cassin
- Department of Obstetrics, Gynecology and Reproductive Sciences, Center for Reproductive Science and Medicine, University of California, San Diego, La Jolla, CA, 92093, USA.
| | - Emily A Witham
- Department of Obstetrics, Gynecology and Reproductive Sciences, Center for Reproductive Science and Medicine, University of California, San Diego, La Jolla, CA, 92093, USA.
| | - Shadi Shojaei
- Department of Obstetrics, Gynecology and Reproductive Sciences, Center for Reproductive Science and Medicine, University of California, San Diego, La Jolla, CA, 92093, USA.
| | - Emily V Ho
- Department of Obstetrics, Gynecology and Reproductive Sciences, Center for Reproductive Science and Medicine, University of California, San Diego, La Jolla, CA, 92093, USA.
| | - Varykina G Thackray
- Department of Obstetrics, Gynecology and Reproductive Sciences, Center for Reproductive Science and Medicine, University of California, San Diego, La Jolla, CA, 92093, USA.
| | - Pamela L Mellon
- Department of Obstetrics, Gynecology and Reproductive Sciences, Center for Reproductive Science and Medicine, University of California, San Diego, La Jolla, CA, 92093, USA.
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Tu C, Fiandalo MV, Pop E, Stocking JJ, Azabdaftari G, Li J, Wei H, Ma D, Qu J, Mohler JL, Tang L, Wu Y. Proteomic Analysis of Charcoal-Stripped Fetal Bovine Serum Reveals Changes in the Insulin-like Growth Factor Signaling Pathway. J Proteome Res 2018; 17:2963-2977. [PMID: 30014700 DOI: 10.1021/acs.jproteome.8b00135] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Charcoal-stripped fetal bovine serum (CS-FBS) is commonly used to study androgen responsiveness and androgen metabolism in cultured prostate cancer (CaP) cells. Switching CaP cells from FBS to CS-FBS may reduce the activity of androgen receptor (AR), inhibit cell proliferation, or modulate intracellular androgen metabolism. The removal of proteins by charcoal stripping may cause changes in biological functions and has not yet been investigated. Here we profiled proteins in FBS and CS-FBS using an ion-current-based quantitative platform consisting of reproducible surfactant-aided precipitation/on-pellet digestion, long-column nanoliquid chromatography separation, and ion-current-based analysis. A total of 143 proteins were identified in FBS, among which 14 proteins including insulin-like growth factor 2 (IGF-2) and IGF binding protein (IGFBP)-2 and -6 were reduced in CS-FBS. IGF-1 receptor (IGF1R) and insulin receptor were sensitized to IGFs in CS-FBS. IGF-1 and IGF-2 stimulation fully compensated for the loss of AR activity to maintain cell growth in CS-FBS. Endogenous production of IGF and IGFBPs was verified in CaP cells and clinical CaP specimens. This study provided the most comprehensive protein profiles of FBS and CS-FBS and offered an opportunity to identify new protein regulators and signaling pathways that regulate AR activity, androgen metabolism, and proliferation of CaP cells.
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Affiliation(s)
- Chengjian Tu
- Department of Pharmaceutical Sciences , State University of New York at Buffalo , 285 Kapoor Hall , Buffalo , New York 14260 , United States.,New York State Center of Excellence in Bioinformatics and Life Sciences , 701 Ellicott Street , Buffalo , New York 14203 , United States
| | - Michael V Fiandalo
- Department of Urology, Roswell Park Comprehensive Cancer Center , Elm and Carlton Streets , Buffalo , New York 14263 , United States
| | - Elena Pop
- Department of Urology, Roswell Park Comprehensive Cancer Center , Elm and Carlton Streets , Buffalo , New York 14263 , United States
| | - John J Stocking
- Department of Urology, Roswell Park Comprehensive Cancer Center , Elm and Carlton Streets , Buffalo , New York 14263 , United States
| | - Gissou Azabdaftari
- Department of Pathology, Roswell Park Comprehensive Cancer Center , Elm and Carlton Streets , Buffalo , New York 14263 , United States
| | - Jun Li
- Department of Pharmaceutical Sciences , State University of New York at Buffalo , 285 Kapoor Hall , Buffalo , New York 14260 , United States.,New York State Center of Excellence in Bioinformatics and Life Sciences , 701 Ellicott Street , Buffalo , New York 14203 , United States
| | - Hua Wei
- Department of Pharmacy, Changzheng Hospital , Second Military Medical University , 415 Fengyang Road , Shanghai 200003 , China
| | - Danjun Ma
- College of Mechanical Engineering , Dongguan University of Technology , 1 Daxue Road , Dongguan , Guangdong 523808 , China
| | - Jun Qu
- Department of Pharmaceutical Sciences , State University of New York at Buffalo , 285 Kapoor Hall , Buffalo , New York 14260 , United States.,New York State Center of Excellence in Bioinformatics and Life Sciences , 701 Ellicott Street , Buffalo , New York 14203 , United States
| | - James L Mohler
- Department of Urology, Roswell Park Comprehensive Cancer Center , Elm and Carlton Streets , Buffalo , New York 14263 , United States
| | - Li Tang
- Department of Cancer Prevention and Control , Roswell Park Comprehensive Cancer Center , Elm and Carlton Streets , Buffalo , New York 14263 , United States
| | - Yue Wu
- Department of Urology, Roswell Park Comprehensive Cancer Center , Elm and Carlton Streets , Buffalo , New York 14263 , United States
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6
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Comparing the rules of engagement of androgen and glucocorticoid receptors. Cell Mol Life Sci 2017; 74:2217-2228. [PMID: 28168446 PMCID: PMC5425506 DOI: 10.1007/s00018-017-2467-3] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2016] [Revised: 12/21/2016] [Accepted: 01/17/2017] [Indexed: 01/22/2023]
Abstract
Despite the diverse physiological activities of androgens and glucocorticoids, the corresponding receptors are very close members of the nuclear-receptor super family. Their action mechanisms show striking similarities, since both receptors recognize very similar DNA-response elements and recruit the same coactivators to their target genes. The specificity of the responses lies mainly in the tissue-specific expression of the receptors and in their ligand specificity. In cells, where both receptors are expressed, the mechanisms leading to the difference in target genes are less obvious. They lie in part in subtle variations of the DNA-binding sites, in cooperativity with other transcription factors and in differential allosteric signals from the DNA and ligand to other receptor domains. We will highlight the different suggestions that might explain the DNA sequence selectivity and will compare the possible allosteric routes between the response elements and the different functions in the transactivation process. The interplay of androgen and glucocorticoid receptors is also highly relevant in clinical settings, where both receptors are therapeutically targeted. We will discuss the possibility that the glucocorticoid and androgen receptors can play partially redundant roles in castration-resistant prostate cancer.
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7
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Zhai W, Sun Y, Jiang M, Wang M, Gasiewicz TA, Zheng J, Chang C. Differential regulation of LncRNA-SARCC suppresses VHL-mutant RCC cell proliferation yet promotes VHL-normal RCC cell proliferation via modulating androgen receptor/HIF-2α/C-MYC axis under hypoxia. Oncogene 2016; 35:4866-80. [PMID: 26973243 DOI: 10.1038/onc.2016.19] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2015] [Revised: 11/22/2015] [Accepted: 12/07/2015] [Indexed: 02/06/2023]
Abstract
It is well established that hypoxia contributes to tumor progression in a hypoxia inducible factor-2α (HIF-2α)-dependent manner in renal cell carcinoma (RCC), yet the role of long noncoding RNAs (LncRNAs) involved in hypoxia-mediated RCC progression remains unclear. Here we demonstrate that LncRNA-SARCC (Suppressing Androgen Receptor in Renal Cell Carcinoma) is differentially regulated by hypoxia in a von Hippel-Lindau (VHL)-dependent manner both in RCC cell culture and clinical specimens. LncRNA-SARCC can suppress hypoxic cell cycle progression in the VHL-mutant RCC cells while derepress it in the VHL-restored RCC cells. Mechanism dissection reveals that LncRNA-SARCC can post-transcriptionally regulate androgen receptor (AR) by physically binding and destablizing AR protein to suppress AR/HIF-2α/C-MYC signals. In return, HIF-2α can transcriptionally regulate the LncRNA-SARCC expression via binding to hypoxia-responsive elements on the promoter of LncRNA-SARCC. The negative feedback modulation between LncRNA-SARCC/AR complex and HIF-2α signaling may then lead to differentially modulated RCC progression in a VHL-dependent manner. Together, these results may provide us a new therapeutic approach via targeting this newly identified signal from LncRNA-SARCC to AR-mediated HIF-2α/C-MYC signals against RCC progression.
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Affiliation(s)
- W Zhai
- Department of Urology, Shanghai Tenth People's Hospital, Tongji University, Shanghai, China.,George Whipple Lab for Cancer Research, Departments of Pathology, Urology, Radiation Oncology and the Wilmot Cancer Center, University of Rochester Medical Center, Rochester, NY, USA
| | - Y Sun
- George Whipple Lab for Cancer Research, Departments of Pathology, Urology, Radiation Oncology and the Wilmot Cancer Center, University of Rochester Medical Center, Rochester, NY, USA
| | - M Jiang
- Lab of Nuclear Receptors and Cancer Research, School of Medicine, Nantong University, Nantong, Jiangsu, China
| | - M Wang
- George Whipple Lab for Cancer Research, Departments of Pathology, Urology, Radiation Oncology and the Wilmot Cancer Center, University of Rochester Medical Center, Rochester, NY, USA
| | - T A Gasiewicz
- Department of Environmental Medicine, University of Rochester Medical Center, Rochester, NY, USA
| | - J Zheng
- Department of Urology, Shanghai Tenth People's Hospital, Tongji University, Shanghai, China
| | - C Chang
- George Whipple Lab for Cancer Research, Departments of Pathology, Urology, Radiation Oncology and the Wilmot Cancer Center, University of Rochester Medical Center, Rochester, NY, USA.,Sex Hormone Research Center, China Medical University/Hospital, Taichung, Taiwan
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8
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Abstract
New incidence of prostate cancer is a major public health issue in the Western world, and has been rising in other areas of the globe in recent years. In an effort to understanding the molecular pathogenesis of this disease, numerous cell models have been developed, arising mostly from patient biopsies. The introduction of the genetically engineered mouse in biomedical research has allowed the development of murine models that allow for the investigation of tumorigenic and metastatic processes. Current challenges to the field include lack of an animal model that faithfully recapitulates bone metastasis of prostate cancer.
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Affiliation(s)
- David Cunningham
- Department of Structural & Cellular Biology, Tulane University Health Sciences Center, New Orleans, LA, USA
| | - Zongbing You
- Department of Structural & Cellular Biology, Tulane University Health Sciences Center, New Orleans, LA, USA
- Department of Orthopaedic Surgery, Tulane University Health Sciences Center, New Orleans, LA, USA
- Tulane Cancer Center and Louisiana Cancer Research Consortium, Tulane University Health Sciences Center, New Orleans, LA, USA
- Tulane Center for Stem Cell Research and Regenerative Medicine, Tulane University Health Sciences Center, New Orleans, LA, USA
- Tulane Center for Aging, Tulane University Health Sciences Center, New Orleans, LA, USA
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9
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Abstract
When the National Institutes of Health Mouse Models of Human Cancer Consortium initiated the Prostate Steering Committee 15 years ago, there were no genetically engineered mouse (GEM) models of prostate cancer (PCa). Today, a PubMed search for "prostate cancer mouse model" yields 3,200 publications and this list continues to grow. The first generation of GEM utilized the newly discovered and characterized probasin promoter driving viral oncogenes such as Simian virus 40 large T antigen to yield the LADY and TRAMP models. As the PCa research field has matured, the second generation of models has incorporated the single and multiple molecular changes observed in human disease, such as loss of PTEN and overexpression of Myc. Application of these models has revealed that mice are particularly resistant to developing invasive PCa, and once they achieve invasive disease, the PCa rarely resembles human disease. Nevertheless, these models and their application have provided vital information on human PCa progression. The aim of this review is to provide a brief primer on mouse and human prostate histology and pathology, provide descriptions of mouse models, as well as attempt to answer the age old question: Which GEM model of PCa is the best for my research question?
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Ottaviani S, Brooke GN, O'Hanlon-Brown C, Waxman J, Ali S, Buluwela L. Characterisation of the androgen regulation of glycine N-methyltransferase in prostate cancer cells. J Mol Endocrinol 2013; 51:301-12. [PMID: 23997240 PMCID: PMC3821059 DOI: 10.1530/jme-13-0169] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The development and growth of prostate cancer is dependent on androgens; thus, the identification of androgen-regulated genes in prostate cancer cells is vital for defining the mechanisms of prostate cancer development and progression and developing new markers and targets for prostate cancer treatment. Glycine N-methyltransferase (GNMT) is a S-adenosylmethionine-dependent methyltransferase that has been recently identified as a novel androgen-regulated gene in prostate cancer cells. Although the importance of this protein in prostate cancer progression has been extensively addressed, little is known about the mechanism of its androgen regulation. Here, we show that GNMT expression is stimulated by androgen in androgen receptor (AR) expressing cells and that the stimulation occurs at the mRNA and protein levels. We have identified an androgen response element within the first exon of the GNMT gene and demonstrated that AR binds to this element in vitro and in vivo. Together, these studies identify GNMT as a direct transcriptional target of the AR. As this is an evolutionarily conserved regulatory element, this highlights androgen regulation as an important feature of GNMT regulation.
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Affiliation(s)
| | - Greg N Brooke
- School of Biological SciencesUniversity of EssexColchesterUK
| | | | | | - Simak Ali
- Correspondence should be addressed to L Buluwela or S Ali, or
| | - Laki Buluwela
- Correspondence should be addressed to L Buluwela or S Ali, or
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11
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Dart DA, Waxman J, Aboagye EO, Bevan CL. Visualising androgen receptor activity in male and female mice. PLoS One 2013; 8:e71694. [PMID: 23940781 PMCID: PMC3737126 DOI: 10.1371/journal.pone.0071694] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2013] [Accepted: 07/08/2013] [Indexed: 11/19/2022] Open
Abstract
Androgens, required for normal development and fertility of males and females, have vital roles in the reproductive tract, brain, cardiovascular system, smooth muscle and bone. Androgens function via the androgen receptor (AR), a ligand-dependent transcription factor. To assay and localise AR activity in vivo we generated the transgenic “ARE-Luc” mouse, expressing a luciferase reporter gene under the control of activated endogenous AR. In vivo imaging of androgen-mediated luciferase activity revealed several strongly expressing tissues in the male mouse as expected and also in certain female tissues. In males the testes, prostate, seminal vesicles and bone marrow all showed high AR activity. In females, strong activity was seen in the ovaries, uterus, omentum tissue and mammary glands. In both sexes AR expression and activity was also found in salivary glands, the eye (and associated glands), adipose tissue, spleen and, notably, regions of the brain. Luciferase protein expression was found in the same cell layers as androgen receptor expression. Additionally, mouse AR expression and activity correlated well with AR expression in human tissues. The anti-androgen bicalutamide reduced luciferase signal in all tissues. Our model demonstrates that androgens can act in these tissues directly via AR, rather than exclusively via androgen aromatisation to estrogens and activation of the estrogen receptor. Additionally, it visually demonstrates the fundamental importance of AR signalling outside the normal role in the reproductive organs. This model represents an important tool for physiological and developmental analysis of androgen signalling, and for characterization of known and novel androgenic or antiandrogenic compounds.
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Affiliation(s)
- D. Alwyn Dart
- Department of Surgery & Cancer, Imperial Centre for Translational and Experimental Medicine, Imperial College London, London, United Kingdom
| | - Jonathan Waxman
- Department of Surgery & Cancer, Imperial Centre for Translational and Experimental Medicine, Imperial College London, London, United Kingdom
| | - Eric O. Aboagye
- Department of Surgery & Cancer, Imperial Centre for Translational and Experimental Medicine, Imperial College London, London, United Kingdom
| | - Charlotte L. Bevan
- Department of Surgery & Cancer, Imperial Centre for Translational and Experimental Medicine, Imperial College London, London, United Kingdom
- * E-mail:
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12
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Cluning C, Ward BK, Rea SL, Arulpragasam A, Fuller PJ, Ratajczak T. The helix 1-3 loop in the glucocorticoid receptor LBD is a regulatory element for FKBP cochaperones. Mol Endocrinol 2013; 27:1020-35. [PMID: 23686112 DOI: 10.1210/me.2012-1023] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
The heat-shock protein 90 (Hsp90) cochaperone FK506-binding protein 52 (FKBP52) upregulates, whereas FKBP51 inhibits, hormone binding and nuclear targeting of the glucocorticoid receptor (GR). Decreased cortisol sensitivity in the guinea pig is attributed to changes within the helix 1 to helix 3 (H1-H3) loop of the guinea pig GR (gpGR) ligand-binding domain. It has been proposed that this loop serves as a contact point for FKBP52 and/or FKBP51 with receptor. We examined the role of the H1-H3 loop in GR activation by FKBP52 using a Saccharomyces cerevisiae model. The activity of rat GR (rGR) containing the gpGR H1-H3 loop substitutions was still potentiated by FKBP52, confirming the loop is not involved in primary FKBP52 interactions. Additional assays also excluded a role for other intervening loops between ligand-binding domain helices in direct interactions with FKBP52 associated with enhanced receptor activity. Complementary studies in FKBP51-deficient mouse embryo fibroblasts and HEK293 cells demonstrated that substitution of the gpGR H1-H3 loop residues into rGR dramatically increased receptor repression by FKBP51 without enhancing receptor-FKBP51 interaction and did not alter recruitment of endogenous Hsp90 and the p23 cochaperone to receptor complexes. FKBP51 suppression of the mutated rGR did not require FKBP51 peptidylprolyl cis-trans isomerase activity and was not disrupted by mutation of the FK1 proline-rich loop thought to mediate reciprocal FKBP influences on receptor activity. We conclude that the gpGR-specific mutations within the H1-H3 loop confer global changes within the GR-Hsp90 complex that favor FKBP51 repression over FKBP52 potentiation, thus identifying the loop as an important target for GR regulation by the FKBP cochaperones.
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Affiliation(s)
- Carmel Cluning
- Laboratory for Molecular Endocrinology, Western Australian Institute forMedical Research and the UWA Centre for Medical Research, The University of Western Australia, Australia
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13
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Phosphorylation of the androgen receptor by PIM1 in hormone refractory prostate cancer. Oncogene 2012; 32:3992-4000. [PMID: 22986532 PMCID: PMC3527659 DOI: 10.1038/onc.2012.412] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2011] [Revised: 07/13/2012] [Accepted: 07/25/2012] [Indexed: 12/11/2022]
Abstract
Integration of cellular signaling pathways with androgen receptor (AR) signaling can be achieved through phosphorylation of AR by cellular kinases. However, the kinases responsible for phosphorylating the androgen receptor at numerous sites and the functional consequences of AR phosphorylation are only partially understood. Bioinformatic analysis revealed AR serine 213 (S213) as a putative substrate for PIM1, a kinase overexpressed in prostate cancer. Therefore, phosphorylation of AR serine 213 by PIM1 was examined using a phosphorylation site-specific antibody. Wild type PIM1, but not catalytically inactive PIM1, specifically phosphorylated AR but not an AR serine to alanine mutant (S213A). In vitro kinase assays confirmed that PIM1 can phosphorylate AR S213 in a ligand independent manner and cell type specific phosphorylation was observed in prostate cancer cell lines. Upon PIM1 overexpression AR phosphorylation was observed in the absence of hormone and was further increased in the presence of hormone in LNCaP, LNCaP-abl, and VCaP cells. Moreover, phosphorylation of AR was reduced in the presence of PIM kinase inhibitors. An examination of AR mediated transcription showed that reporter gene activity was reduced in the presence of PIM1 and wild type AR, but not S213A mutant AR. Androgen mediated transcription of endogenous PSA, Nkx3.1, and IGFBP5 was also decreased in the presence of PIM1 whereas IL6, cyclin A1, and caveolin 2 were increased. Immunohistochemical analysis of prostate cancer tissue microarrays showed significant P-AR S213 expression that was associated with hormone refractory prostate cancers, likely identifying cells with catalytically active PIM1. In addition, prostate cancers expressing a high level of P-AR S213 were twice as likely to be from biochemically recurrent cancers. Thus, AR phosphorylation by PIM1 at S213 impacts gene transcription and is highly prevalent in aggressive prostate cancer.
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14
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Wegner W, Burckhardt BC, Burckhardt G, Henjakovic M. Male-dominant activation of rat renal organic anion transporter 1 (Oat1) and 3 (Oat3) expression by transcription factor BCL6. PLoS One 2012; 7:e35556. [PMID: 22530049 PMCID: PMC3329484 DOI: 10.1371/journal.pone.0035556] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2011] [Accepted: 03/21/2012] [Indexed: 12/14/2022] Open
Abstract
Background Organic anion transporters 1 (Oat1) and 3 (Oat3) mediate the transport of organic anions, including frequently prescribed drugs, across cell membranes in kidney proximal tubule cells. In rats, these transporters are known to be male-dominant and testosterone-dependently expressed. The molecular mechanisms that are involved in the sex-dependent expression are unknown. Our aim was to identify genes that show a sex-dependent expression and could be involved in male-dominant regulation of Oat1 and Oat3. Methodology/Principal Findings Promoter activities of Oat1 and Oat3 were analyzed using luciferase assays. Expression profiling was done using a SurePrint G3 rat GE 8×60K microarray. RNA was isolated from renal cortical slices of four adult rats per sex. To filter the achieved microarray data for genes expressed in proximal tubule cells, transcription database alignment was carried out. We demonstrate that predicted androgen response elements in the promoters of Oat1 and Oat3 are not functional when the promoters were expressed in OK cells. Using microarray analyses we analyzed 17,406 different genes. Out of these genes, 56 exhibit a sex-dependent expression in rat proximal tubule cells. As genes potentially involved in the regulation of Oat1 and Oat3 expression, we identified, amongst others, the male-dominant hydroxysteroid (17-beta) dehydrogenase 1 (Hsd17b1), B-cell CLL/lymphoma 6 (BCL6), and polymerase (RNA) III (DNA directed) polypeptide G (Polr3g). Moreover, our results revealed that the transcription factor BCL6 activates promoter constructs of Oat1 and Oat3. Conclusion The results indicate that the male-dominant expression of both transporters, Oat1 and Oat3, is possibly not directly regulated by the classical androgen receptor mediated transcriptional pathway but appears to be regulated by the transcription factor BCL6.
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Affiliation(s)
| | | | | | - Maja Henjakovic
- Department of Systemic Physiology and Pathophysiology, University Medical Center Göttingen, Göttingen, Germany
- * E-mail:
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15
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Streicher W, Zengerling F, Laschak M, Weidemann W, Höpfner M, Schrader AJ, Jentzmik F, Schrader M, Cronauer MV. AR-Q640X, a model to study the effects of constitutively active C-terminally truncated AR variants in prostate cancer cells. World J Urol 2012; 30:333-9. [PMID: 22362413 DOI: 10.1007/s00345-012-0842-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2011] [Accepted: 02/10/2012] [Indexed: 01/20/2023] Open
Abstract
PURPOSE A recently identified mechanism allowing prostate cancer (PCa) cells to grow in the absence of androgens is the expression of constitutively active, C-terminally truncated androgen receptor (AR) variants lacking vast parts of the ligand-binding domain. These AR variants termed ARΔLBD are either products of alternative splicing, point mutations leading to premature stop codons or proteolytic cleavage of the AR. Some controversies exist about the requirement of additional full-length AR for the full transcriptional activity of the ARΔLBD. On basis of a mutated, C-terminally truncated AR termed Q640X, we developed an experimental model for the study of ARΔLBD in PCa cells. METHODS Activation of AR-dependent promoters was analyzed by reporter gene assays. Dimerization studies were conducted using a mammalian two-hybrid system. RESULTS Although Q640X/Q640X homodimers were able to induce the expression of certain AR target genes, Q640X/AR heterodimers were necessary to activate the full panel of androgen-dependent genes under androgen-deprived conditions. CONCLUSIONS The following study supports the hypothesis that castration-resistant prostate cancer (CRPC) cells are able to activate specific androgen-dependent genes by selective modulation of the ratio between ARΔLBD and their putative dimerization partners like the full-length AR or other ARΔLBD in the absence of androgens. The present data suggest that AR-mutant Q640X is a powerful experimental tool for the functional analysis of ARΔLBD in CRPC.
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Affiliation(s)
- Wolfgang Streicher
- Department of Urology, Research Laboratory, University of Ulm, Prittwitzstrasse 43, 89075, Ulm, Germany
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16
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Zhang Y, Shaik AA, Xing C, Chai Y, Li L, Zhang J, Zhang W, Kim SH, Lü J, Jiang C. A synthetic decursin analog with increased in vivo stability suppresses androgen receptor signaling in vitro and in vivo. Invest New Drugs 2011; 30:1820-9. [PMID: 21870073 DOI: 10.1007/s10637-011-9738-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2011] [Accepted: 08/14/2011] [Indexed: 11/30/2022]
Abstract
Targeting androgen receptor (AR) signaling with agents distinct from current antagonist drugs remains a rational approach to the prevention and treatment of prostate cancer (PCa). Our previous studies have shown that decursin and isomer decursinol angelate (DA), isolated from the Korean medicinal herb Angelica gigas Nakai, interrupt AR signaling and possess anti-PCa activities in vitro. In the LNCaP PCa cell model, these pyranoccoumarin compounds exhibit properties distinct from currently used antagonists (e.g., Casodex). However, both are rapidly de-esterified to decursinol, a partial AR agonist. We report here that a synthetic decursin analog, decursinol phenylthiocarbamate (DPTC), has greater in vivo stability than the parent compounds. DPTC-decursinol conversion was undetectable in mice. Furthermore, in LNCaP cells, DPTC decreased prostate specific antigen (PSA) expression, down-regulated AR abundance and mRNA and inhibited AR nuclear translocation. The effect of DPTC on AR and PSA mRNA and protein abundance was also observed in VCaP cells expressing wild type AR. DPTC inhibited growth of both PCa cell lines through G(1) cell cycle arrest and apoptosis, as did decursin and DA. Furthermore, i.p. administration of DPTC for 3 weeks suppressed the expression of AR target genes probasin and Nkx3.1 in mouse prostate glands. Overall, our data suggest that DPTC represents a prototype lead compound for development of in vivo stable and active novel decursin analogs for the prevention or therapy of PCa.
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Affiliation(s)
- Yong Zhang
- Hormel Institute, University of Minnesota, Austin, MN 55912, USA
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17
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Liu Q, Su S, Blackwelder AJ, Minges JT, Wilson EM. Gain in transcriptional activity by primate-specific coevolution of melanoma antigen-A11 and its interaction site in androgen receptor. J Biol Chem 2011; 286:29951-63. [PMID: 21730049 DOI: 10.1074/jbc.m111.244715] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Male sex development and growth occur in response to high affinity androgen binding to the androgen receptor (AR). In contrast to complete amino acid sequence conservation in the AR DNA and ligand binding domains among mammals, a primate-specific difference in the AR NH(2)-terminal region that regulates the NH(2)- and carboxyl-terminal (N/C) interaction enables direct binding to melanoma antigen-A11 (MAGE-11), an AR coregulator that is also primate-specific. Human, mouse, and rat AR share the same NH(2)-terminal (23)FQNLF(27) sequence that mediates the androgen-dependent N/C interaction. However, the mouse and rat AR FXXLF motif is flanked by Ala(33) that evolved to Val(33) in primates. Human AR Val(33) was required to interact directly with MAGE-11 and for the inhibitory effect of the AR N/C interaction on activation function 2 that was relieved by MAGE-11. The functional importance of MAGE-11 was indicated by decreased human AR regulation of an androgen-dependent endogenous gene using lentivirus short hairpin RNAs and by the greater transcriptional strength of human compared with mouse AR. MAGE-11 increased progesterone and glucocorticoid receptor activity independently of binding an FXXLF motif by interacting with p300 and p160 coactivators. We conclude that the coevolution of the AR NH(2)-terminal sequence and MAGE-11 expression among primates provides increased regulatory control over activation domain dominance. Primate-specific expression of MAGE-11 results in greater steroid receptor transcriptional activity through direct interactions with the human AR FXXLF motif region and indirectly through steroid receptor-associated p300 and p160 coactivators.
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Affiliation(s)
- Qiang Liu
- Laboratories for Reproductive Biology, Lineberger Comprehensive Cancer Center, University of North Carolina, Chapel Hill, North Carolina 27599-7500, USA
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18
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Murashima A, Miyagawa S, Ogino Y, Nishida-Fukuda H, Araki K, Matsumoto T, Kaneko T, Yoshinaga K, Yamamura KI, Kurita T, Kato S, Moon AM, Yamada G. Essential roles of androgen signaling in Wolffian duct stabilization and epididymal cell differentiation. Endocrinology 2011; 152:1640-51. [PMID: 21303954 PMCID: PMC3060634 DOI: 10.1210/en.2010-1121] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The epididymis is a male accessory organ and functions for sperm maturation and storage under the control of androgen. The development of the epididymis is also androgen dependent. The Wolffian duct (WD), anlagen of the epididymis, is formed in both male and female embryos; however, it is stabilized only in male embryos by testicular androgen. Androgen drives subsequent differentiation of the WD into the epididymis. Although the essential roles of androgen in WD masculinization and epididymal function have been established, little is known about cellular events regulated precisely by androgen signaling during these processes. It is also unclear whether androgen signaling, especially in the epithelia, has further function for epididymal epithelial cell differentiation. In this study we examined the cellular death and proliferation controlled by androgen signaling via the androgen receptor (AR) in WD stabilization. Analyses using AR knockout mice revealed that androgen signaling inhibits epithelial cell death in this process. Analysis of AP2α-Cre;AR(flox/Y) mice, in which AR function is deleted in the WD epithelium, revealed that epithelial AR is not required for the WD stabilization but is required for epithelial cell differentiation in the epididymis. Specifically, loss of epithelial AR significantly reduced expression of p63 that is essential for differentiation of basal cells in the epididymal epithelium. We also interrogated the possibility of regulation of the p63 gene (Trp63) by AR in vitro and found that p63 is a likely direct target of AR regulation.
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Affiliation(s)
- Aki Murashima
- Institute of Molecular Embryology and Genetics, Graduate School of Medical and Pharmaceutical Sciences, Global Center of Excellence Cell Fate Regulation Research and Education Unit, Kumamoto University, Kumamoto 860-0811, Japan
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19
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Anose BM, Sanders MM. Androgen Receptor Regulates Transcription of the ZEB1 Transcription Factor. Int J Endocrinol 2011; 2011:903918. [PMID: 22190929 PMCID: PMC3235469 DOI: 10.1155/2011/903918] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/01/2011] [Accepted: 09/15/2011] [Indexed: 11/17/2022] Open
Abstract
The zinc finger E-box binding protein 1 (ZEB1) transcription factor belongs to a two-member family of zinc-finger homeodomain proteins involved in physiological and pathological events mostly relating to cell migration and epithelial to mesenchymal transitions (EMTs). ZEB1 (also known as δEF1, zfhx1a, TCF8, and Zfhep) plays a key role in regulating such diverse processes as T-cell development, skeletal patterning, reproduction, and cancer cell metastasis. However, the factors that regulate its expression and consequently the signaling pathways in which ZEB1 participates are poorly defined. Because it is induced by estrogen and progesterone and is high in prostate cancer, we investigated whether tcf8, which encodes ZEB1, is regulated by androgen. Data herein demonstrate that tcf8 is induced by dihydrotestosterone (DHT) in the human PC-3/AR prostate cancer cell line and that this induction is mediated by two androgen response elements (AREs). These results demonstrate that ZEB1 is an intermediary in androgen signaling pathways.
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Affiliation(s)
- Bynthia M. Anose
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
- Department of Chemistry, Bethel University, St. Paul, MN 55112, USA
| | - Michel M. Sanders
- Department of Biochemistry, Molecular Biology and Biophysics, University of Minnesota, Minneapolis, MN 55455, USA
- *Michel M. Sanders:
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20
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Zhang J, Gao N, DeGraff DJ, Yu X, Sun Q, Case TC, Kasper S, Matusik RJ. Characterization of cis elements of the probasin promoter necessary for prostate-specific gene expression. Prostate 2010; 70:934-51. [PMID: 20209642 PMCID: PMC3712623 DOI: 10.1002/pros.21128] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
BACKGROUND The androgen-regulated probasin (PB) promoter has been used extensively to target transgenes to the prostate in transgenic mice; however, limited data exist on the mechanism that dictates prostate-specific gene expression. Tissue-specific gene expression involves synergistic effects among transcription factors associated in a complex bound to cis-acting DNA elements. METHODS Using comprehensive linker scan mutagenesis, enzyme mobility shift and supershift assays, chromatin immunoprecipitation, and transgenic animal studies, we have extensively characterized the prostate-specific PB promoter. RESULTS We identified a series of nonreceptor transcription factors that are bound to the prostate-specific rat PB promoter. These factors include several ubiquitously distributed proteins known to participate in steroid receptor-mediated transcription. In addition, we identified two tissue-specific DNA elements that are crucial in directing prostate-specific PB expression, and confirmed the functional importance of both elements in transgenic animal studies. These two elements are functionally interchangeable and can be bound by multiple protein complexes, including the forkhead transcription factor FoxA1, a "pioneer factor" that has a restricted distribution to some cells type that are ectoderm and endoderm in origin. Using transgenic mice, we further demonstrate that the minimal PB promoter region (-244/-96 bp) that encompasses these tissue-specific elements results in prostate-specific gene expression in transgenic mice, contains androgen receptor and FoxA1-binding sites, as well as ubiquitous transcription factor binding sites. CONCLUSION We propose that these sequence-specific DNA-binding proteins, including tissue-restricted and ubiquitous factors, create the first level of transcriptional control, which responds to intracellular pathways that directs prostate-specific gene expression.
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Affiliation(s)
- JianFeng Zhang
- Department of Cell and Developmental Biology, Nashville, TN 37232-2765 USA
| | - Nan Gao
- Department of Cell and Developmental Biology, Nashville, TN 37232-2765 USA
- Department of Urologic Surgery, Nashville, TN 37232-2765 USA
| | - David J. DeGraff
- Department of Cell and Developmental Biology, Nashville, TN 37232-2765 USA
- Department of Urologic Surgery, Nashville, TN 37232-2765 USA
- Department of Vanderbilt University Medical Center, Nashville, TN 37232-2765 USA
| | - Xiuping Yu
- Department of Urologic Surgery, Nashville, TN 37232-2765 USA
| | - Qian Sun
- Department of Cancer Biology and Vanderbilt-Ingram Cancer Center, Nashville, TN 37232-2765 USA
| | - Thomas C. Case
- Department of Urologic Surgery, Nashville, TN 37232-2765 USA
| | - Susan Kasper
- Department of Environmental Health, University of Cincinnati, Cincinnati OH 45267-0056
| | - Robert J. Matusik
- Department of Cell and Developmental Biology, Nashville, TN 37232-2765 USA
- Department of Urologic Surgery, Nashville, TN 37232-2765 USA
- Department of Cancer Biology and Vanderbilt-Ingram Cancer Center, Nashville, TN 37232-2765 USA
- Department of Vanderbilt University Medical Center, Nashville, TN 37232-2765 USA
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21
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Denayer S, Helsen C, Thorrez L, Haelens A, Claessens F. The rules of DNA recognition by the androgen receptor. Mol Endocrinol 2010; 24:898-913. [PMID: 20304998 DOI: 10.1210/me.2009-0310] [Citation(s) in RCA: 114] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
The androgen receptor (AR) and glucocorticoid, progestagen, and mineralocorticoid receptors all recognize classical DNA response elements that are organized as inverted repeats of 5'-AGAACA-3'-like motifs with a three-nucleotide spacer. Next to such elements, the AR also recognizes a second type of androgen response element (ARE), the so-called selective AREs, which resemble more the direct repeats of the same hexamer. In this work, we show that not only the AR but also the progestagen receptor can recognize the selective AREs, whereas neither glucocorticoid nor mineralocorticoid receptor can. Recently, genomic AR-binding fragments have been postulated to contain AR-binding sites that diverge considerably from the classical ARE consensus. Extensive mutational analyses of these candidate motifs, however, reinstalls the values of the consensus sequence for the AREs as mentioned above, the importance of their dimeric nature and the presence of exactly three-nucleotide spacing. We developed a position-specific probability matrix that was used to predict with higher accuracy new AREs in different AR-binding regions. So far, all AR-binding genomic fragments that were analyzed contain AREs defined as receptor-dimer binding motifs with the ability to confer responsiveness to a reporter gene.
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Affiliation(s)
- Sarah Denayer
- Katholieke Universiteit Leuven, Campus Gasthuisberg, O/N1, Herestraat 49, 3000 Leuven, Belgium
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22
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Zhang KX, Jia W, Rennie PS. Bioengineered viral vectors for targeting and killing prostate cancer cells. Bioeng Bugs 2010; 1:92-6. [PMID: 21326934 PMCID: PMC3026449 DOI: 10.4161/bbug.1.2.11102] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2009] [Accepted: 01/04/2010] [Indexed: 02/06/2023] Open
Abstract
Enabling the transduction of therapeutic gene expression exclusively in diseased sites is the key to developing more effective treatments for advanced prostate cancer using viral-based therapy. While prostate cancers that express high levels of HER-2 are resistant to the killing effects of trastuzumab, they can be targeted for selective gene expression and destruction by lentiviruses with envelope proteins engineered to bind to this therapeutic antibody. More importantly, after intravenous injection, this trastuzumab-bound lentivirus is able to target castration-resistant prostate tumor xenografts, albeit with low efficiency. This proof of principle opens up multiple possibilities for the prevention and treatment of prostate cancer using a viral-based therapy. However, to be safe and more effective, the viral vectors must target prostate cancer cells more selectively and efficiently. A higher degree of specificity and efficiency of cancer cell targeting can be achieved by engineering viral vectors to bind to a specific cell surface marker and by controlling the expression of the therapeutic payload at transcriptional level, with a tissue-specific promoter, and at the translational level, with a regulatory sequences inserted into either the 5'UTR or 3'UTR regions of the therapeutic gene(s). The latter would be designed to ensure that translation of this mRNA occurs exclusively in malignant cells. Furthermore, in order to obtain a potent anti-tumor effect, viral vectors would be engineered to express pro-apoptotic genes, intra-cellar antibodies/nucleotide aptamers to block critical proteins, or siRNAs to knockdown essential cellular mRNAs. Alternatively, controlled expression of an essential viral gene would restore replication competence to the virus and enable selective oncolysis of tumor cells. Successful delivery of such bioengineered viruses may provide a more effective way to treat advanced prostate cancer.
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Affiliation(s)
- Kai-xin Zhang
- The Vancouver Prostate Centre, Vancouver, BC, Canada
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23
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Dart DA, Spencer-Dene B, Gamble SC, Waxman J, Bevan CL. Manipulating prohibitin levels provides evidence for an in vivo role in androgen regulation of prostate tumours. Endocr Relat Cancer 2009; 16:1157-69. [PMID: 19635783 PMCID: PMC2782800 DOI: 10.1677/erc-09-0028] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Current hormonal therapies for prostate cancer are effective initially, but inevitably tumours progress to an advanced, metastatic stage, often referred to as 'androgen independent'. However, the androgen receptor (AR) signalling pathway is still key for their growth. It is speculated that tumours escape hormonal control via reduction in corepressor proteins. Manipulating such proteins is thus a potential therapeutic strategy to halt or even reverse tumour progression. We aimed to elucidate the effects of altering levels of the AR corepressor and androgen-target protein prohibitin (PHB) on prostate tumour growth. Prostate cancer cells incorporating an integrated androgen-responsive reporter gene and stably expressing vectors to inducibly overexpress or knockdown PHB were generated and used to assess effects on androgen signalling (by real time imaging) and tumour growth both in culture and in vivo. PHB overexpression inhibited AR activity and prostate-specific antigen (PSA) expression as well as androgen-dependent growth of cells, inducing rapid accumulation in G(0)/G(1). Conversely, reduction in PHB increased AR activity, PSA expression, androgen-mediated growth and S-phase entry. In vivo, doxycycline-induced PHB regulation resulted in marked changes in AR activity, and showed significant effects upon tumour growth. Overexpression led to tumour growth arrest and protection from hormonal starvation, whereas RNAi knockdown resulted in accelerated tumour growth, even in castrated mice. This study provides proof of principle that i) reduction in PHB promotes both androgen-dependent and 'androgen-independent' tumour growth, and ii) altering AR activity via increasing levels or activity of corepressors is a valid therapeutic strategy for advanced prostate cancer.
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Affiliation(s)
- D Alwyn Dart
- Androgen Signalling Laboratory, Department of Oncology, Imperial College London, Du Cane Road, London, W12 0NN, UK
| | - Bradley Spencer-Dene
- Department of Histopathology, Imperial College London and Experimental Pathology Laboratory, Cancer Research UK, Lincoln's Inn Fields, London, WC2A 3PX,, UK
| | - Simon C Gamble
- Androgen Signalling Laboratory, Department of Oncology, Imperial College London, Du Cane Road, London, W12 0NN, UK
| | - Jonathan Waxman
- Androgen Signalling Laboratory, Department of Oncology, Imperial College London, Du Cane Road, London, W12 0NN, UK
| | - Charlotte L Bevan
- Androgen Signalling Laboratory, Department of Oncology, Imperial College London, Du Cane Road, London, W12 0NN, UK
- Correspondence should be addressed to C L Bevan;
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24
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The prostate of weaned pups is altered by maternal malnutrition during lactation in rats. Asian J Androl 2009; 12:180-5. [PMID: 19935672 DOI: 10.1038/aja.2009.69] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
The aim of this study was to evaluate the effects of maternal malnutrition during lactation on prostate growth and estradiol serum concentration in the prostate of pups. At delivery, nine Wistar rats were separated into three groups: control group (C) with free access to a standard laboratory diet containing 22% protein; protein-energy-restricted group (PER) with free access to an isoenergy and protein-restricted diet containing 8% protein; and energy-restricted group (ER) receiving standard laboratory diet in restricted quantities, which were calculated according to the mean ingestion of the PER group. All pups were killed at weaning. PER and ER groups presented a significant reduction in estradiol serum concentration (C = 73.8 +/- 4.6, PER = 48.7 +/- 3.2, ER = 59.7 +/- 5.5 pg mL(-1), P < 0.01), total prostatic acini (C = 24 190.0 +/- 716.5, PER = 20 290.0 +/- 631.4, ER = 19 550.0 +/- 759.1 microm(2); P < 0.01), lumen of the prostatic acini (C = 5 590.0 +/- 165.4, PER = 3 776.0 +/- 251.3, ER = 4 658.0 +/- 198.1 microm(2); P < 0.01) and epithelial area of the prostate dorsal lobe (C = 18 120.0 +/- 391.4, PER = 16 520.0 +/- 799.2, ER = 14 890.0 +/- 589.8 microm(2); P < 0.01). Testosterone concentration was significantly increased only in the PER group when compared with the C group (C = 0.09 +/- 0.01, PER = 0.44 +/- 0.04, ER = 0.15 +/- 0.03 ng mL(-1), P < 0.001). An adequate nutritional state in early life is important for normal growth of the prostate gland, which seem to be related to serum levels of estradiol.
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25
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Lin B, Wang J, Hong X, Yan X, Hwang D, Cho JH, Yi D, Utleg AG, Fang X, Schones DE, Zhao K, Omenn GS, Hood L. Integrated expression profiling and ChIP-seq analyses of the growth inhibition response program of the androgen receptor. PLoS One 2009; 4:e6589. [PMID: 19668381 PMCID: PMC2720376 DOI: 10.1371/journal.pone.0006589] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2009] [Accepted: 07/09/2009] [Indexed: 01/06/2023] Open
Abstract
Background The androgen receptor (AR) plays important roles in the development of male phenotype and in different human diseases including prostate cancers. The AR can act either as a promoter or a tumor suppressor depending on cell types. The AR proliferative response program has been well studied, but its prohibitive response program has not yet been thoroughly studied. Methodology/Principal Findings Previous studies found that PC3 cells expressing the wild-type AR inhibit growth and suppress invasion. We applied expression profiling to identify the response program of PC3 cells expressing the AR (PC3-AR) under different growth conditions (i.e. with or without androgens and at different concentration of androgens) and then applied the newly developed ChIP-seq technology to identify the AR binding regions in the PC3 cancer genome. A surprising finding was that the comparison of MOCK-transfected PC3 cells with AR-transfected cells identified 3,452 differentially expressed genes (two fold cutoff) even without the addition of androgens (i.e. in ethanol control), suggesting that a ligand independent activation or extremely low-level androgen activation of the AR. ChIP-Seq analysis revealed 6,629 AR binding regions in the cancer genome of PC3 cells with an FDR (false discovery rate) cut off of 0.05. About 22.4% (638 of 2,849) can be mapped to within 2 kb of the transcription start site (TSS). Three novel AR binding motifs were identified in the AR binding regions of PC3-AR cells, and two of them share a core consensus sequence CGAGCTCTTC, which together mapped to 27.3% of AR binding regions (1,808/6,629). In contrast, only about 2.9% (190/6,629) of AR binding sites contains the canonical AR matrix M00481, M00447 and M00962 (from the Transfac database), which is derived mostly from AR proliferative responsive genes in androgen dependent cells. In addition, we identified four top ranking co-occupancy transcription factors in the AR binding regions, which include TEF1 (Transcriptional enhancer factor), GATA (GATA transcription factors), OCT (octamer transcription factors) and PU1 (PU.1 transcription factor). Conclusions/Significance Our data provide a valuable data set in understanding the molecular basis for growth inhibition response program of the AR in prostate cancer cells, which can be exploited for developing novel prostate cancer therapeutic strategies.
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Affiliation(s)
- Biaoyang Lin
- Department of Urology, University of Washington, Seattle, WA, USA.
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26
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Claessens F, Denayer S, Van Tilborgh N, Kerkhofs S, Helsen C, Haelens A. Diverse roles of androgen receptor (AR) domains in AR-mediated signaling. NUCLEAR RECEPTOR SIGNALING 2008; 6:e008. [PMID: 18612376 PMCID: PMC2443950 DOI: 10.1621/nrs.06008] [Citation(s) in RCA: 167] [Impact Index Per Article: 10.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/18/2008] [Accepted: 05/29/2008] [Indexed: 01/07/2023]
Abstract
Androgens control male sexual development and maintenance of the adult male phenotype. They have very divergent effects on their target organs like the reproductive organs, muscle, bone, brain and skin. This is explained in part by the fact that different cell types respond differently to androgen stimulus, even when all these responses are mediated by the same intracellular androgen receptor. To understand these tissue- and cell-specific readouts of androgens, we have to learn the many different steps in the transcription activation mechanisms of the androgen receptor (NR3C4). Like all nuclear receptors, the steroid receptors have a central DNA-binding domain connected to a ligand-binding domain by a hinge region. In addition, all steroid receptors have a relatively large amino-terminal domain. Despite the overall structural homology with other nuclear receptors, the androgen receptor has several specific characteristics which will be discussed here. This receptor can bind two types of androgen response elements (AREs): one type being similar to the classical GRE/PRE-type elements, the other type being the more divergent and more selective AREs. The hormone-binding domain has low intrinsic transactivation properties, a feature that correlates with the low affinity of this domain for the canonical LxxLL-bearing coactivators. For the androgen receptor, transcriptional activation involves the alternative recruitment of coactivators to different regions in the amino-terminal domain, as well as the hinge region. Finally, a very strong ligand-induced interaction between the amino-terminal domain and the ligand-binding domain of the androgen receptor seems to be involved in many aspects of its function as a transcription factor. This review describes the current knowledge on the structure-function relationships within the domains of the androgen receptor and tries to integrate the involvement of different domains, subdomains and motifs in the functioning of this receptor as a transcription factor with tissue- and cell-specific readouts.
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Affiliation(s)
- Frank Claessens
- Molecular Endocrinology Laboratory, Campus Gasthuisberg, University of Leuven, Leuven, Belgium.
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27
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Bolton EC, So AY, Chaivorapol C, Haqq CM, Li H, Yamamoto KR. Cell- and gene-specific regulation of primary target genes by the androgen receptor. Genes Dev 2007; 21:2005-17. [PMID: 17699749 PMCID: PMC1948856 DOI: 10.1101/gad.1564207] [Citation(s) in RCA: 279] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2007] [Accepted: 07/06/2007] [Indexed: 01/08/2023]
Abstract
The androgen receptor (AR) mediates the physiologic and pathophysiologic effects of androgens including sexual differentiation, prostate development, and cancer progression by binding to genomic androgen response elements (AREs), which influence transcription of AR target genes. The composition and context of AREs differ between genes, thus enabling AR to confer multiple regulatory functions within a single nucleus. We used expression profiling of an immortalized human prostate epithelial cell line to identify 205 androgen-responsive genes (ARGs), most of them novel. In addition, we performed chromatin immunoprecipitation to identify 524 AR binding regions and validated in reporter assays the ARE activities of several such regions. Interestingly, 67% of our AREs resided within approximately 50 kb of the transcription start sites of 84% of our ARGs. Indeed, most ARGs were associated with two or more AREs, and ARGs were sometimes themselves linked in gene clusters containing up to 13 AREs and 12 ARGs. AREs appeared typically to be composite elements, containing AR binding sequences adjacent to binding motifs for other transcriptional regulators. Functionally, ARGs were commonly involved in prostate cell proliferation, communication, differentiation, and possibly cancer progression. Our results provide new insights into cell- and gene-specific mechanisms of transcriptional regulation of androgen-responsive gene networks.
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Affiliation(s)
- Eric C. Bolton
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, California 94143, USA
| | - Alex Y. So
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, California 94143, USA
- Chemistry and Chemical Biology Graduate Program, University of California, San Francisco, California 94143, USA
| | - Christina Chaivorapol
- Department of Biochemistry and Biophysics, University of California, San Francisco, California 94143, USA
- California Institute for Quantitative Biomedical Research, University of California, San Francisco, California 94143, USA
- Graduate Program in Biological and Medical Informatics, University of California, San Francisco, California 94143, USA
| | - Christopher M. Haqq
- Department of Urology, University of California, San Francisco, California 94143, USA
| | - Hao Li
- Department of Biochemistry and Biophysics, University of California, San Francisco, California 94143, USA
- California Institute for Quantitative Biomedical Research, University of California, San Francisco, California 94143, USA
- Graduate Program in Biological and Medical Informatics, University of California, San Francisco, California 94143, USA
| | - Keith R. Yamamoto
- Department of Cellular and Molecular Pharmacology, University of California, San Francisco, California 94143, USA
- Chemistry and Chemical Biology Graduate Program, University of California, San Francisco, California 94143, USA
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28
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Jariwala U, Prescott J, Jia L, Barski A, Pregizer S, Cogan JP, Arasheben A, Tilley WD, Scher HI, Gerald WL, Buchanan G, Coetzee GA, Frenkel B. Identification of novel androgen receptor target genes in prostate cancer. Mol Cancer 2007; 6:39. [PMID: 17553165 PMCID: PMC1904239 DOI: 10.1186/1476-4598-6-39] [Citation(s) in RCA: 70] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2007] [Accepted: 06/06/2007] [Indexed: 12/13/2022] Open
Abstract
BACKGROUND The androgen receptor (AR) plays critical roles in both androgen-dependent and castrate-resistant prostate cancer (PCa). However, little is known about AR target genes that mediate the receptor's roles in disease progression. RESULTS Using Chromatin Immunoprecipitation (ChIP) Display, we discovered 19 novel loci occupied by the AR in castrate resistant C4-2B PCa cells. Only four of the 19 AR-occupied regions were within 10-kb 5'-flanking regulatory sequences. Three were located up to 4-kb 3' of the nearest gene, eight were intragenic and four were in gene deserts. Whereas the AR occupied the same loci in C4-2B (castrate resistant) and LNCaP (androgen-dependent) PCa cells, differences between the two cell lines were observed in the response of nearby genes to androgens. Among the genes strongly stimulated by DHT in C4-2B cells--D-dopachrome tautomerase (DDT), Protein kinase C delta (PRKCD), Glutathione S- transferase theta 2 (GSTT2), Transient receptor potential cation channel subfamily V member 3 (TRPV3), and Pyrroline-5-carboxylate reductase 1 (PYCR1)--most were less strongly or hardly stimulated in LNCaP cells. Another AR target gene, ornithine aminotransferase (OAT), was AR-stimulated in a ligand-independent manner, since it was repressed by AR siRNA knockdown, but not stimulated by DHT. We also present evidence for in vivo AR-mediated regulation of several genes identified by ChIP Display. For example, PRKCD and PYCR1, which may contribute to PCa cell growth and survival, are expressed in PCa biopsies from primary tumors before and after ablation and in metastatic lesions in a manner consistent with AR-mediated stimulation. CONCLUSION AR genomic occupancy is similar between LNCaP and C4-2B cells and is not biased towards 5' gene flanking sequences. The AR transcriptionally regulates less than half the genes nearby AR-occupied regions, usually but not always, in a ligand-dependent manner. Most are stimulated and a few are repressed. In general, response is stronger in C4-2B compared to LNCaP cells. Some of the genes near AR-occupied regions appear to be regulated by the AR in vivo as evidenced by their expression levels in prostate cancer tumors of various stages. Several AR target genes discovered in the present study, for example PRKCD and PYCR1, may open avenues in PCa research and aid the development of new approaches for disease management.
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MESH Headings
- Adenocarcinoma/genetics
- Adenocarcinoma/metabolism
- Androgens
- Binding Sites
- Cell Adhesion Molecules/biosynthesis
- Cell Adhesion Molecules/genetics
- Cell Line, Tumor/drug effects
- Cell Line, Tumor/metabolism
- Chromosomes, Human/drug effects
- Chromosomes, Human/metabolism
- Dihydrotestosterone/pharmacology
- Extracellular Matrix Proteins/biosynthesis
- Extracellular Matrix Proteins/genetics
- Gene Expression Profiling
- Gene Expression Regulation, Neoplastic/drug effects
- Glutathione Transferase/biosynthesis
- Glutathione Transferase/genetics
- Humans
- Intracellular Signaling Peptides and Proteins/genetics
- Male
- Mucin-6
- Mucins/biosynthesis
- Mucins/genetics
- Neoplasm Proteins/biosynthesis
- Neoplasm Proteins/genetics
- Neoplasms, Hormone-Dependent/genetics
- Neoplasms, Hormone-Dependent/metabolism
- Nuclear Proteins/biosynthesis
- Nuclear Proteins/genetics
- Oligonucleotide Array Sequence Analysis
- Ornithine-Oxo-Acid Transaminase/biosynthesis
- Ornithine-Oxo-Acid Transaminase/genetics
- Prostatic Neoplasms/genetics
- Prostatic Neoplasms/metabolism
- Protein Kinase C-delta/biosynthesis
- Protein Kinase C-delta/genetics
- Pyrroline Carboxylate Reductases/biosynthesis
- Pyrroline Carboxylate Reductases/genetics
- Receptors, Androgen/genetics
- Receptors, Androgen/physiology
- TRPV Cation Channels/biosynthesis
- TRPV Cation Channels/genetics
- Transcription, Genetic
- delta-1-Pyrroline-5-Carboxylate Reductase
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Affiliation(s)
- Unnati Jariwala
- Department of Biochemistry and Molecular Biology, Keck School of Medicine, University of Southern California, Los Angeles, USA
| | - Jennifer Prescott
- Department of Preventive Medicine, Keck School of Medicine, University of Southern California, Los Angeles, USA
| | - Li Jia
- Department of Urology, Keck School of Medicine, University of Southern California, Los Angeles, USA
| | - Artem Barski
- Department of Biochemistry and Molecular Biology, Keck School of Medicine, University of Southern California, Los Angeles, USA
| | - Steve Pregizer
- Department of Biochemistry and Molecular Biology, Keck School of Medicine, University of Southern California, Los Angeles, USA
| | - Jon P Cogan
- Department of Biochemistry and Molecular Biology, Keck School of Medicine, University of Southern California, Los Angeles, USA
| | - Armin Arasheben
- Department of Biochemistry and Molecular Biology, Keck School of Medicine, University of Southern California, Los Angeles, USA
| | - Wayne D Tilley
- Dame Roma Mitchell Cancer Research Laboratories, School of Medicine, The University of Adelaide/Hanson Institute, Adelaide, Australia
| | - Howard I Scher
- Genitourinary Oncology Service, Division of Solid Tumor Oncology, Memorial Sloan-Kettering Cancer Center, Department of Medicine, Joan and Sanford I. Weill College of Medicine, New York, NY, USA
| | - William L Gerald
- Genitourinary Oncology Service, Division of Solid Tumor Oncology, Memorial Sloan-Kettering Cancer Center, Department of Medicine, Joan and Sanford I. Weill College of Medicine, New York, NY, USA
| | - Grant Buchanan
- Department of Preventive Medicine, Keck School of Medicine, University of Southern California, Los Angeles, USA
- Department of Urology, Keck School of Medicine, University of Southern California, Los Angeles, USA
- Dame Roma Mitchell Cancer Research Laboratories, School of Medicine, The University of Adelaide/Hanson Institute, Adelaide, Australia
| | - Gerhard A Coetzee
- Department of Preventive Medicine, Keck School of Medicine, University of Southern California, Los Angeles, USA
- Department of Urology, Keck School of Medicine, University of Southern California, Los Angeles, USA
| | - Baruch Frenkel
- Department of Biochemistry and Molecular Biology, Keck School of Medicine, University of Southern California, Los Angeles, USA
- Department of Orthopedic Surgery, Keck School of Medicine, University of Southern California, Los Angeles, USA
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29
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Schauwaers K, De Gendt K, Saunders PTK, Atanassova N, Haelens A, Callewaert L, Moehren U, Swinnen JV, Verhoeven G, Verrijdt G, Claessens F. Loss of androgen receptor binding to selective androgen response elements causes a reproductive phenotype in a knockin mouse model. Proc Natl Acad Sci U S A 2007; 104:4961-6. [PMID: 17360365 PMCID: PMC1829247 DOI: 10.1073/pnas.0610814104] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Androgens influence transcription of their target genes through the activation of the androgen receptor (AR) that subsequently interacts with specific DNA motifs in these genes. These DNA motifs, called androgen response elements (AREs), can be classified in two classes: the classical AREs, which are also recognized by the other steroid hormone receptors; and the AR-selective AREs, which display selectivity for the AR. For in vitro interaction with the selective AREs, the androgen receptor DNA-binding domain is dependent on specific residues in its second zinc-finger. To evaluate the physiological relevance of these selective elements, we generated a germ-line knockin mouse model, termed SPARKI (SPecificity-affecting AR KnockIn), in which the second zinc-finger of the AR was replaced with that of the glucocorticoid receptor, resulting in a chimeric protein that retains its ability to bind classical AREs but is unable to bind selective AREs. The reproductive organs of SPARKI males are smaller compared with wild-type animals, and they are also subfertile. Intriguingly, however, they do not display any anabolic phenotype. The expression of two testis-specific, androgen-responsive genes is differentially affected by the SPARKI mutation, which is correlated with the involvement of different types of response elements in their androgen responsiveness. In this report, we present the first in vivo evidence of the existence of two functionally different types of AREs and demonstrate that AR-regulated gene expression can be targeted based on this distinction.
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Affiliation(s)
- Kris Schauwaers
- *Molecular Endocrinology Laboratory, Department of Molecular Cell Biology, and
| | - Karel De Gendt
- Laboratory for Experimental Medicine and Endocrinology, Department of Developmental Biology, Catholic University of Leuven, Campus Gasthuisberg, Herestraat 49, B-3000 Leuven, Belgium
| | - Philippa T. K. Saunders
- Medical Research Council Human Reproductive Sciences Unit, 47 Little France Crescent, Edinburgh EH16 4TJ, Scotland; and
| | - Nina Atanassova
- Institute of Experimental Morphology and Anthropology with Museum, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
| | - Annemie Haelens
- *Molecular Endocrinology Laboratory, Department of Molecular Cell Biology, and
| | - Leen Callewaert
- *Molecular Endocrinology Laboratory, Department of Molecular Cell Biology, and
| | - Udo Moehren
- *Molecular Endocrinology Laboratory, Department of Molecular Cell Biology, and
| | - Johannes V. Swinnen
- Laboratory for Experimental Medicine and Endocrinology, Department of Developmental Biology, Catholic University of Leuven, Campus Gasthuisberg, Herestraat 49, B-3000 Leuven, Belgium
| | - Guido Verhoeven
- Laboratory for Experimental Medicine and Endocrinology, Department of Developmental Biology, Catholic University of Leuven, Campus Gasthuisberg, Herestraat 49, B-3000 Leuven, Belgium
| | - Guy Verrijdt
- *Molecular Endocrinology Laboratory, Department of Molecular Cell Biology, and
| | - Frank Claessens
- *Molecular Endocrinology Laboratory, Department of Molecular Cell Biology, and
- Laboratory for Experimental Medicine and Endocrinology, Department of Developmental Biology, Catholic University of Leuven, Campus Gasthuisberg, Herestraat 49, B-3000 Leuven, Belgium
- To whom correspondence should be addressed. E-mail:
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30
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Mantoni TS, Reid G, Garrett MD. Androgen receptor activity is inhibited in response to genotoxic agents in a p53-independent manner. Oncogene 2006; 25:3139-49. [PMID: 16434973 DOI: 10.1038/sj.onc.1209347] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The androgen receptor (AR) is fundamental to androgen signalling within the prostate gland, and deregulation of its activity is frequently linked to the development of prostate cancer. Advanced prostate cancer is often treated with chemotherapy and most of these drugs exert their function by generating genotoxic stress such as DNA damage. We have investigated here the effects of genotoxic agents used in chemotherapeutic regimens on AR function and expression. We have discovered that endogenous AR activity in LNCaP cells is inhibited in response to the chemotherapeutic agents etoposide and cisplatin. This loss of AR activity is not caused by a change in cell cycle distribution, a change in subcellular localisation of the AR nor by induction of apoptosis. In addition, we found that inhibition of AR activity in response to genotoxic stress is independent of p53 function. Interestingly, our studies revealed that genotoxic stress inhibits the hormone-stimulated recruitment of AR to androgen response elements. Thus, we report for the first time a mechanism by which the AR activity is inhibited in response to different chemotherapeutic agents.
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31
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Drake CG, Doody AD, Mihalyo MA, Huang CT, Kelleher E, Ravi S, Hipkiss EL, Flies DB, Kennedy EP, Long M, McGary PW, Coryell L, Nelson WG, Pardoll DM, Adler AJ. Androgen ablation mitigates tolerance to a prostate/prostate cancer-restricted antigen. Cancer Cell 2005; 7:239-49. [PMID: 15766662 PMCID: PMC2846360 DOI: 10.1016/j.ccr.2005.01.027] [Citation(s) in RCA: 235] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2004] [Revised: 10/18/2004] [Accepted: 01/31/2005] [Indexed: 12/23/2022]
Abstract
To understand the T cell response to prostate cancer, we created transgenic mice that express a model antigen in a prostate-restricted pattern and crossed these animals to TRAMP mice that develop spontaneous prostate cancer. Adoptive transfer of prostate-specific CD4 T cells shows that, in the absence of prostate cancer, the prostate gland is mostly ignored. Tumorigenesis allows T cell recognition of the prostate gland--but this recognition is tolerogenic, resulting in abortive proliferation and ultimately in hyporesponsiveness at the systemic level. Androgen ablation (the most common treatment for metastatic prostate cancer) was able to mitigate this tolerance--allowing prostate-specific T cells to expand and develop effector function after vaccination. These results suggest that immunotherapy for prostate cancer may be most efficacious when administered after androgen ablation.
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Affiliation(s)
- Charles G. Drake
- Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, Maryland 21231
| | - Amy D.H. Doody
- Center for Immunotherapy of Cancer and Infectious Diseases, University of Connecticut Health Center, Farmington, Connecticut 06030
| | - Marianne A. Mihalyo
- Center for Immunotherapy of Cancer and Infectious Diseases, University of Connecticut Health Center, Farmington, Connecticut 06030
| | - Ching-Tai Huang
- Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, Maryland 21231
| | - Erin Kelleher
- Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, Maryland 21231
| | - Sowmya Ravi
- Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, Maryland 21231
| | - Edward L. Hipkiss
- Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, Maryland 21231
| | - Dallas B. Flies
- Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, Maryland 21231
| | - Eugene P. Kennedy
- Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, Maryland 21231
| | - Meixiao Long
- Center for Immunotherapy of Cancer and Infectious Diseases, University of Connecticut Health Center, Farmington, Connecticut 06030
| | - Patrick W. McGary
- Center for Immunotherapy of Cancer and Infectious Diseases, University of Connecticut Health Center, Farmington, Connecticut 06030
| | - Lee Coryell
- Center for Immunotherapy of Cancer and Infectious Diseases, University of Connecticut Health Center, Farmington, Connecticut 06030
| | - William G. Nelson
- Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, Maryland 21231
| | - Drew M. Pardoll
- Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins, Baltimore, Maryland 21231
| | - Adam J. Adler
- Center for Immunotherapy of Cancer and Infectious Diseases, University of Connecticut Health Center, Farmington, Connecticut 06030
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32
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Shaffer PL, Jivan A, Dollins DE, Claessens F, Gewirth DT. Structural basis of androgen receptor binding to selective androgen response elements. Proc Natl Acad Sci U S A 2004; 101:4758-63. [PMID: 15037741 PMCID: PMC387321 DOI: 10.1073/pnas.0401123101] [Citation(s) in RCA: 259] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Steroid receptors bind as dimers to a degenerate set of response elements containing inverted repeats of a hexameric half-site separated by 3 bp of spacer (IR3). Naturally occurring selective androgen response elements have recently been identified that resemble direct repeats of the hexameric half-site (ADR3). The 3D crystal structure of the androgen receptor (AR) DNA-binding domain bound to a selective ADR3 reveals an unexpected head-to-head arrangement of the two protomers rather than the expected head-to-tail arrangement seen in nuclear receptors bound to response elements of similar geometry. Compared with the glucocorticoid receptor, the DNA-binding domain dimer interface of the AR has additional interactions that stabilize the AR dimer and increase the affinity for nonconsensus response elements. This increased interfacial stability compared with the other steroid receptors may account for the selective binding of AR to ADR3 response elements.
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Affiliation(s)
- Paul L Shaffer
- Department of Biochemistry, Duke University Medical Center, Durham, NC 27710, USA
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33
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Wafa LA, Cheng H, Rao MA, Nelson CC, Cox M, Hirst M, Sadowski I, Rennie PS. Isolation and identification of L-dopa decarboxylase as a protein that binds to and enhances transcriptional activity of the androgen receptor using the repressed transactivator yeast two-hybrid system. Biochem J 2003; 375:373-83. [PMID: 12864730 PMCID: PMC1223690 DOI: 10.1042/bj20030689] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2003] [Revised: 07/10/2003] [Accepted: 07/15/2003] [Indexed: 11/17/2022]
Abstract
The AR (androgen receptor) is a ligand-regulated transcription factor, which belongs to the steroid receptor family and plays an essential role in growth and development of the prostate. Transcriptional activity of steroid receptors is modulated by interaction with co-regulator proteins and yeast two-hybrid analysis is commonly used to identify these steroid receptor-interacting proteins. However, a limitation of conventional two-hybrid systems for detecting AR protein partners has been that they only allow for analysis of the ligand- and DNA-binding domains of the receptor, as its NTD (N-terminal domain) possesses intrinsic transactivation activity. To identify AR N-terminus-interacting proteins, its NTD was used in the RTA (repressed transactivator) system, which is specifically designed for transactivator bait proteins and was shown to be suitable for two-hybrid analysis with the AR NTD. DDC (L-dopa decarboxylase) was detected multiple times as a novel AR-interacting protein, which was subsequently confirmed in vitro and in vivo. Furthermore, transient transfection of DDC in prostate cancer cells strongly enhanced ligand-dependent AR transcriptional activity, an effect that was antagonized using high concentrations of the anti-androgen bicalutamide. Glucocorticoid receptor activity was also strongly enhanced with DDC co-transfection, while oestrogen receptor activity was only mildly affected. Together, our data demonstrate that DDC interacts with AR to enhance steroid receptor transactivation, which may have important implications in prostate cancer progression.
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MESH Headings
- Amino Acid Sequence
- Anilides/pharmacology
- Animals
- Binding Sites/genetics
- Blotting, Western
- Cell Line, Tumor
- Dopa Decarboxylase/genetics
- Dopa Decarboxylase/metabolism
- Estrogen Receptor alpha
- Gene Expression Regulation, Enzymologic
- Gene Expression Regulation, Neoplastic
- Humans
- Luciferases/genetics
- Luciferases/metabolism
- Male
- Molecular Sequence Data
- Nitriles
- Protein Binding
- Rats
- Receptors, Androgen/genetics
- Receptors, Androgen/metabolism
- Receptors, Estrogen/genetics
- Receptors, Estrogen/metabolism
- Receptors, Glucocorticoid/genetics
- Receptors, Glucocorticoid/metabolism
- Recombinant Fusion Proteins/genetics
- Recombinant Fusion Proteins/metabolism
- Saccharomyces cerevisiae/genetics
- Tosyl Compounds
- Transcriptional Activation/drug effects
- Two-Hybrid System Techniques
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Affiliation(s)
- Latif A Wafa
- Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, BC, V6T 2B5, Canada
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34
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Nightingale J, Chaudhary KS, Abel PD, Stubbs AP, Romanska HM, Mitchell SE, Stamp GWH, Lalani EN. Ligand activation of the androgen receptor downregulates E-cadherin-mediated cell adhesion and promotes apoptosis of prostatic cancer cells. Neoplasia 2003; 5:347-61. [PMID: 14511406 PMCID: PMC1502422 DOI: 10.1016/s1476-5586(03)80028-3] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2003] [Accepted: 04/25/2003] [Indexed: 11/23/2022]
Abstract
Androgen independence is the major cause of endocrine therapy failure in advanced prostate cancer (PC). To examine the effects of human androgen receptor (AR) expression on growth of human PC cells, transfection of full-length AR cDNA in an androgen-insensitive human prostatic adenocarcinoma cell line (DU145) was performed. Transcriptional activity of AR was confirmed by the MMTV luciferase assay and AR expression was assessed by reverse transcriptase polymerase chain reaction, Western blotting, and immunocytochemistry. Two stable transfectant cell lines expressing functional AR were established and passaged over 60 times. Under standard culture conditions, AR expression in transfected cells was predominantly cytoplasmic. Exposure to dihydrotestosterone (DHT; 60 pM-10 nM) resulted in a rapid (maximal at 30 minutes) translocation of AR to the nucleus. Treatment with DHT (5 nM) caused a significant reduction in cell-cell adhesion and aggregation accompanied by a decrease in E-cadherin expression. This was associated with up to 40% inhibition of proliferation and approximately two-fold increase in apoptosis. These results suggest that gene transfer-mediated AR expression in DU145 cells confers sensitivity to DHT, modulates cell-cell adhesion through E-cadherin, and suppresses cell growth by inhibiting proliferation and promoting apoptosis. This provides amodelfor studies ofAR-regulated cell signalling and identification of novel androgen-regulated genes in PC.
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Affiliation(s)
- Joanna Nightingale
- Department of Histopathology Imperial College, Hammersmith Campus, London W12 0NN, UK
| | - Khurram S Chaudhary
- Department of Histopathology Imperial College, Hammersmith Campus, London W12 0NN, UK
| | - Paul D Abel
- Department of Surgery, Imperial College, Hammersmith Campus, London W12 0NN, UK
| | - Andrew P Stubbs
- Department of Histopathology Imperial College, Hammersmith Campus, London W12 0NN, UK
| | - Hanna M Romanska
- Department of Histopathology Imperial College, Hammersmith Campus, London W12 0NN, UK
| | - Stephen E Mitchell
- Department of Histopathology Imperial College, Hammersmith Campus, London W12 0NN, UK
| | - Gordon W H Stamp
- Department of Histopathology Imperial College, Hammersmith Campus, London W12 0NN, UK
| | - El-Nasir Lalani
- Department of Histopathology Imperial College, Hammersmith Campus, London W12 0NN, UK
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35
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Yeung LHY, Read JT, Sorenson P, Nelson CC, Jia W, Rennie PS. Identification and characterization of a prostate-specific androgen-independent protein-binding site in the probasin promoter. Biochem J 2003; 371:843-55. [PMID: 12540291 PMCID: PMC1223328 DOI: 10.1042/bj20021816] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2002] [Revised: 01/22/2003] [Accepted: 01/23/2003] [Indexed: 01/03/2023]
Abstract
In this study we investigated the combination of transcription factors and proteins binding to the proximal part of the prostate-specific probasin (PB) promoter. Using DNaseI in vitro footprinting, several protected regions were identified on the proximal PB promoter (nucleotides -286 to +28 relative to the transcription start site) when nuclear extracts from LNCaP, a human prostate cancer cell line, were used. Four of the protected areas were observed only when LNCaP nuclear extracts treated with synthetic androgen (10 nM R1881) were used. Two other regions, referred to as FPI and FPII, showed protection regardless of the presence or absence of androgen. When DNaseI footprinting was done using other prostate and non-prostate nuclear extracts, protection of the FPII region was only seen in prostate cell lines. These androgen-independent regions were further tested for tissue and binding specificity using the electrophoretic mobility-shift assay. Eight complexes formed with the FPI probe while four complexes were observed with the FPII probe on incubation with the tested nuclear extracts. Methylation protection assays reveal that prostate cancer cell lines yield slightly different protection patterns for some of the protein complexes formed with non-prostate-derived cell lines, suggesting the presence of prostate-enriched or -exclusive proteins. Site-directed mutagenesis of the protected nucleotides within FPII resulted in a significant reduction in expression from the PB promoter. Identification of proteins binding to the FPII region revealed the participation of nuclear factor I (NF-I) or a closely related protein, although other unknown proteins are also involved. Defining the DNA and protein components that dictate prostate-specific expression of the PB promoter in an androgen-independent manner would provide a strong basis for the design and development of a gene therapy for systemic treatment of androgen-independent prostate cancer.
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Affiliation(s)
- Lillian H Y Yeung
- Department of Pathology and Laboratory Medicine, University of British Columbia, and The Prostate Centre, Vancouver General Hospital, Canada.
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36
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Haelens A, Verrijdt G, Callewaert L, Christiaens V, Schauwaers K, Peeters B, Rombauts W, Claessens F. DNA recognition by the androgen receptor: evidence for an alternative DNA-dependent dimerization, and an active role of sequences flanking the response element on transactivation. Biochem J 2003; 369:141-51. [PMID: 12350223 PMCID: PMC1223063 DOI: 10.1042/bj20020912] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2002] [Revised: 08/23/2002] [Accepted: 09/26/2002] [Indexed: 12/17/2022]
Abstract
The androgen receptor has a subset of target DNA sequences, which are not recognized by any other steroid receptors. The androgen selectivity of these sequences was proposed to be the consequence of the ability of the androgen receptor to dimerize on direct repeats of 5'-TGTTCT-3'-like sequences. This is in contrast with the classical non-selective elements consisting of inverted repeats of the 5'-TGTTCT-3' elements separated by three nucleotides and which are recognized by other steroid receptors in addition to the androgen receptor. We demonstrate that while the DNA-binding domain of the oestrogen receptor is unable to dimerize on direct repeats, dimeric binding can be rescued by replacing the second Zn finger and part of the hinge region by the corresponding fragment of the androgen receptor, but not the glucocorticoid receptor. In this study, we investigate the androgen receptor binding to all natural androgen-selective response elements described so far. We show that a 12-amino acid C-terminal extension of the DNA-binding domain is required for high-affinity binding of the androgen receptor to all these elements. For one androgen-specific low-affinity binding site, the flanking sequences do not contribute to the in vitro affinity of the androgen receptor DNA-binding domain. Surprisingly, however, they control the transcriptional activity of the androgen receptor in transient transfection experiments. In conclusion, we give evidence that the alternative DNA-dependent dimerization of the androgen receptor on direct repeats is a general mechanism for androgen specificity in which the second Zn finger and hinge region are involved. In addition, the sequences flanking an androgen-response element can control the activity of the androgen receptor.
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Affiliation(s)
- Annemie Haelens
- Division of Biochemistry, Faculty of Medicine, Campus Gasthuisberg, University of Leuven, Herestraat 49, B-3000 Leuven, Belgium
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37
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Chesire DR, Isaacs WB. Ligand-dependent inhibition of beta-catenin/TCF signaling by androgen receptor. Oncogene 2002; 21:8453-69. [PMID: 12466965 DOI: 10.1038/sj.onc.1206049] [Citation(s) in RCA: 120] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2002] [Revised: 09/10/2002] [Accepted: 09/16/2002] [Indexed: 11/09/2022]
Abstract
Beta-catenin signaling may contribute to prostate cancer (CaP) progression. Although beta-catenin is known to upregulate T cell factor (TCF) target gene expression in CaP cells, recent evidence demonstrates its capacity to enhance ligand-dependent androgen receptor (AR) function. Thus, we wished to further understand the interaction between these two pathways. We find in both CaP cells (CWR22-Rv1, LAPC-4, DU145) and non-CaP cells (HEK-293, TSU, SW480, HCT-116) that beta-catenin/TCF-related transcription (CRT), as measured by activation of a synthetic promoter and that of cyclin D1, is inhibited by androgen treatment. This inhibition is AR-dependent, as it only occurs in cells expressing AR endogenously or transiently, and is abrogated by AR antagonists. Additional analyses convey that the ligand-dependent nature of CRT suppression depends on transactivation-competent AR in the nucleus, but not on indirect effects stemming from AR target gene expression. Given the recent work identifying an AR/beta-catenin interaction, and from our finding that liganded AR does not prompt gross changes in the constitutive nuclear localization of TCF4 or mutant beta-catenin, we hypothesized that transcription factor (i.e. AR and TCF) competition for beta-catenin recruitment may explain, in part, androgen-induced suppression of CRT. To address this idea, we expressed an AR mutant lacking its DNA-binding domain (DBD). This receptor could not orchestrate ligand-dependent CRT repression, thereby providing support for those recent data implicating the AR DBD/LBD as necessary for beta-catenin interaction. Further supporting this hypothesis, TCF/LEF over-expression counteracts androgen-induced suppression of CRT, and requires beta-catenin binding activity to do so. Interestingly, TCF4 over-expression potently antagonizes AR function; however, this inhibition may occur independently of beta-catenin/TCF4 interaction. These results from TCF4 over-expression analyses, taken together, provide further evidence that AR-mediated suppression of CRT is a consequence of limiting amounts of beta-catenin, and not AR target gene expression. Our analyses point to a reciprocal balance between AR and CRT function that may shape critical processes during normal prostate development and tumor progression.
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Affiliation(s)
- Dennis R Chesire
- Brady Urological Institute Research Laboratories, The Johns Hopkins Medical Institutions, Baltimore, Maryland, MD 21287, USA
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Logg CR, Logg A, Matusik RJ, Bochner BH, Kasahara N. Tissue-specific transcriptional targeting of a replication-competent retroviral vector. J Virol 2002; 76:12783-91. [PMID: 12438603 PMCID: PMC136666 DOI: 10.1128/jvi.76.24.12783-12791.2002] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2002] [Accepted: 09/13/2002] [Indexed: 01/06/2023] Open
Abstract
The inability of replication-defective viral vectors to efficiently transduce tumor cells in vivo has prevented the successful application of such vectors in gene therapy of cancer. To address the need for more efficient gene delivery systems, we have developed replication-competent retroviral (RCR) vectors based on murine leukemia virus (MLV). We have previously shown that such vectors are capable of transducing solid tumors in vivo with very high efficiency. While the natural requirement of MLV infection for cell division imparts a certain degree of specificity for tumor cells, additional means for confining RCR vector replication to tumor cells are desirable. Here, we investigated the parameters critical for successful tissue-specific transcriptional control of RCR vector replication by replacing various lengths of the MLV enhancer/promoter with sequences derived either from the highly prostate-specific probasin (PB) promoter or from a more potent synthetic variant of the PB promoter. We assessed the transcriptional specificity of the resulting hybrid long terminal repeats (LTRs) and the cell type specificity and efficiency of replication of vectors containing these LTRs. Incorporation of PB promoter sequences effectively restricted transcription from the LTR to prostate-derived cells and imparted prostate-specific RCR vector replication but required the stronger synthetic promoter and retention of native MLV sequences in the vicinity of the TATA box for optimal replicative efficiency and specificity. Our results have thus identified promoter strength and positioning within the LTR as important determinants for achieving both high transduction efficiency and strict cell type specificity in transcriptionally targeted RCR vectors.
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Affiliation(s)
- Christopher R Logg
- Institute for Genetic Medicine, Keck School of Medicine, University of Southern California, 2250 Alcazar Street, Los Angeles, CA 90033, USA
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39
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Mitchell S, Abel P, Madaan S, Jeffs J, Chaudhary K, Stamp G, Lalani EN. Androgen-dependent regulation of human MUC1 mucin expression. Neoplasia 2002; 4:9-18. [PMID: 11922395 PMCID: PMC1503313 DOI: 10.1038/sj.neo.7900194] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2001] [Revised: 07/09/2001] [Indexed: 11/09/2022]
Abstract
MUC1 mucin is transcriptionally regulated by estrogen, progesterone, and glucocorticoids. Our objective was to determine whether androgen receptor (AR) activation regulates expression of MUC1. The following breast and prostatic cell lines were phenotyped and grouped according to AR and MUC1 protein expression: 1) AR+MUC1 + [DAR17+19 (AR transfectants of DU-145), ZR-75-1, MDA-MB-453, and T47D]; 2) AR-MUC1 + [DZeo1 (AR-vector control), DU-145, BT20, MDA-MB-231, and MCF7]; 3) AR+MUC1 - (LNCaP and LNCaP-r). Cell proliferation was determined using the MTT assay in the presence of synthetic androgen R1881, 0.1 microM to 1 microM. Cell surface MUC1 expression was determined by flow cytometry in the presence or absence of oestradiol, medroxy progesterone acetate or R1881, with and without 4 hydroxy-flutamide (4-OH), a nonsteroidal AR antagonist. The functional significance of MUC1 expression was investigated with a cell-cell aggregation assay. Only AR+MUC1 + cell lines showed a significant increase in MUC1 expression with AR activation (P (range) =.01 to .0001), reversed in the presence of 4-OHF. Cell proliferation was unaffected. Increased expression of MUC1 was associated with a significant (P (range) = .002 to .001) reduction in cell-cell adhesion. To our knowledge, this is the first description of androgen-dependent regulation of MUC1 mucin. This is also functionally associated with decreased cell-cell adhesion, a recognised feature of progressive malignancy. These findings have important implications for physiological and pathological processes.
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Affiliation(s)
- Stephen Mitchell
- Department of Histopathology Faculty of Medicine, Imperial College, Hammersmith Hospital Campus, Du Cane Road, London W12 0NN, UK
- Department of Surgery Faculty of Medicine, Imperial College, Hammersmith Hospital Campus, Du Cane Road, London W12 0NN, UK
| | - Paul Abel
- Department of Surgery Faculty of Medicine, Imperial College, Hammersmith Hospital Campus, Du Cane Road, London W12 0NN, UK
| | - Sanjeev Madaan
- Department of Histopathology Faculty of Medicine, Imperial College, Hammersmith Hospital Campus, Du Cane Road, London W12 0NN, UK
- Department of Surgery Faculty of Medicine, Imperial College, Hammersmith Hospital Campus, Du Cane Road, London W12 0NN, UK
| | - James Jeffs
- Department of Statistical Consultancy Service, Faculty of Medicine, Imperial College, Hammersmith Hospital Campus, Du Cane Road, London W12 0NN, UK
| | - Khurram Chaudhary
- Department of Histopathology Faculty of Medicine, Imperial College, Hammersmith Hospital Campus, Du Cane Road, London W12 0NN, UK
| | - Gordon Stamp
- Department of Histopathology Faculty of Medicine, Imperial College, Hammersmith Hospital Campus, Du Cane Road, London W12 0NN, UK
| | - El-Nasir Lalani
- Department of Histopathology Faculty of Medicine, Imperial College, Hammersmith Hospital Campus, Du Cane Road, London W12 0NN, UK
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40
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Lu B, Smock SL, Castleberry TA, Owen TA. Molecular cloning and functional characterization of the canine androgen receptor. Mol Cell Biochem 2001; 226:129-40. [PMID: 11768233 DOI: 10.1023/a:1012752107129] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
Sex steroids, including testosterone, play a major role in determining peak bone mass in mammals and the subsequent loss of total bone mass with advancing age. Testosterone, and its active metabolite dihydrotestosterone (DHT), bind with high affinity to the androgen receptor (AR), a member of the nuclear hormone receptor superfamily. These receptors function as transcription factors, binding together with accessory proteins to specific DNA response elements in the promoters of androgen responsive genes. To further characterize AR function in a model species of relevance to bone and pharmaceutical research, we cloned a partial canine AR from a canine kidney cDNA library and then cloned the remaining 5' segment by PCR from canine ventral prostate cDNA. The complete sequence obtained was 3577 bp. This sequence contained a single open reading frame of 2721 bp, potentially encoding a protein of 907 amino acids with a predicted molecular weight of 98.7 kD. Sequence analysis of the protein encoded by this open reading frame reveals that the modular domains providing the DNA binding and ligand binding functions are identical to those reported for eight other mammalian ARs. Northern analysis of poly-A+ RNA from ventral prostate revealed three very low abundance transcripts of approximately 9 kb and RT-PCR analysis showed relatively high expression of AR in canine ventral prostate, testis, and kidney, with lower levels detectable in spleen, skeletal muscle, heart, and liver. Competition binding studies using 3H-DHT as ligand demonstrated specific displacement by DHT, testosterone, and the anabolic steroid stanozolol, with IC50 values of 1.3, 2.5 and 3.8 nM, respectively. Binding of DHT also resulted in the stimulation of an androgen responsive-luciferase reporter following cotransfection with the canine AR into 293 cells. Immunohistochemistry using an antibody directed to the C-terminal 19 amino acids of the human AR showed strong staining of the secretory epithelial cells in canine ventral prostate. Together, these data indicate that we have cloned the canine AR and that its functional DNA binding and ligand binding domains are absolutely conserved with those reported for eight other species.
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MESH Headings
- Amino Acid Sequence
- Animals
- Base Sequence
- Blotting, Northern
- Cell Line
- Cloning, Molecular
- DNA/metabolism
- DNA, Complementary/metabolism
- Dogs
- Dose-Response Relationship, Drug
- Gene Library
- Humans
- Immunohistochemistry
- Inhibitory Concentration 50
- Kidney/metabolism
- Ligands
- Liver/metabolism
- Luciferases/metabolism
- Male
- Molecular Sequence Data
- Muscle, Skeletal/metabolism
- Myocardium/metabolism
- Prostate/metabolism
- Protein Binding
- RNA, Messenger/metabolism
- Receptors, Androgen/chemistry
- Receptors, Androgen/genetics
- Reverse Transcriptase Polymerase Chain Reaction
- Sequence Homology, Amino Acid
- Sequence Homology, Nucleic Acid
- Spleen/metabolism
- Testis/metabolism
- Tissue Distribution
- Transcriptional Activation
- Transfection
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Affiliation(s)
- B Lu
- Department of Cardiovascular and Metabolic Diseases, Pfizer Global Research and Development, Groton, CT 06340, USA
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41
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Stanbrough M, Leav I, Kwan PW, Bubley GJ, Balk SP. Prostatic intraepithelial neoplasia in mice expressing an androgen receptor transgene in prostate epithelium. Proc Natl Acad Sci U S A 2001; 98:10823-8. [PMID: 11535819 PMCID: PMC58558 DOI: 10.1073/pnas.191235898] [Citation(s) in RCA: 133] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Prostate cancer (PCa) is an androgen dependent disease that can be treated by androgen ablation therapy, and clinical trials are under way to prevent PCa through the reduction of androgen receptor (AR) activity. However, there are no animal models of AR-mediated prostatic neoplasia, and it remains unclear whether the AR is a positive or negative regulator of cell growth in normal prostate secretory epithelium. To assess the direct effects of the AR in prostate epithelium, a murine AR transgene regulated by the rat probasin promoter (Pb) was used to generate transgenic mice expressing increased levels of AR protein in prostate secretory epithelium. The prostates in younger (<1 year) Pb-mAR transgenic mice were histologically normal, but Ki-67 immunostaining revealed marked increases in epithelial proliferation in ventral prostate and dorsolateral prostate. Older (>1 year) transgenic mice developed focal areas of intraepithelial neoplasia strongly resembling human high-grade prostatic intraepithelial neoplasia (PIN), a precursor to PCa. These results demonstrate that the AR is a positive regulator of cell growth in normal prostate epithelium and provide a model system of AR-stimulated PIN that can be used for assessing preventative hormonal therapies and for identifying secondary transforming events relevant to human PCa.
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Affiliation(s)
- M Stanbrough
- Cancer Biology Program, Hematology-Oncology Division, Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, 330 Brookline Avenue, Boston, MA 02215, USA
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42
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Whitacre DC, Karnas KJ, Miesfeld RL. Analysis of glucocorticoid and androgen receptor gene fusions delineates domains required for transcriptional specificity. Endocrine 2001; 15:111-8. [PMID: 11572317 DOI: 10.1385/endo:15:1:111] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Androgen receptor (AR) and glucocorticoid receptor (GR) influence distinct physiologic responses in steroid-responsive cells despite their shared ability to selectively bind in vitro to the same canonical DNA sequence (TGTTCT). While the DNA-binding domains (DBDs) of these receptors are highly conserved, the amino N-terminal domain (NTD) and hormone-binding domain (HBD) are evolutionarily divergent. To determine the relative contribution of these functional domains to steroid-specific effects in vivo, we constructed a panel of AR/GR gene fusions by interchanging the NTD, DBD, and HBD regions of each receptor and measured transcriptional regulatory activities in transfected kidney and prostate cell lines. We found that GR was approximately 10-fold more active than AR when tested with the mouse mammary tumor virus promoter, and that this difference in activity was primarily owing to sequence divergence in the NTDs. We also tested transcriptional activation of the androgen-dependent rat probasin promoter, and in this case, AR was at least twofold more active than GR. Analysis of the chimeric receptors revealed that this difference mapped to the DBD region of the two receptors. Transcriptional repression functions of the wild-type and chimeric receptors were measured using an activator protein 1 (AP-1) transrepression assay and identified the GR HBD as a more potent transrepressor of AP-1 transcriptional activation than the AR HBD. Taken together, our analyses reveal that evolutionary sequence divergence between AR and GR functional domains results in unique promoter-specific activities within biologic systems in which both AR and GR are normally expressed.
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MESH Headings
- Amino Acid Sequence
- Androgen-Binding Protein/genetics
- Animals
- Binding Sites
- DNA/metabolism
- Humans
- Male
- Mammary Tumor Virus, Mouse/genetics
- Molecular Sequence Data
- Mutagenesis, Site-Directed
- Peptide Fragments/chemistry
- Peptide Fragments/genetics
- Promoter Regions, Genetic
- Prostate/chemistry
- Rats
- Receptors, Androgen/chemistry
- Receptors, Androgen/genetics
- Receptors, Androgen/physiology
- Receptors, Glucocorticoid/chemistry
- Receptors, Glucocorticoid/genetics
- Receptors, Glucocorticoid/physiology
- Recombinant Fusion Proteins
- Structure-Activity Relationship
- Transcription Factor AP-1/metabolism
- Transcription, Genetic
- Transfection
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Affiliation(s)
- D C Whitacre
- Department of Molecular and Cellular Biology, University of Arizona, Tucson 85721, USA
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43
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Müller JM, Isele U, Metzger E, Rempel A, Moser M, Pscherer A, Breyer T, Holubarsch C, Buettner R, Schüle R. FHL2, a novel tissue-specific coactivator of the androgen receptor. EMBO J 2000; 19:359-69. [PMID: 10654935 PMCID: PMC305573 DOI: 10.1093/emboj/19.3.359] [Citation(s) in RCA: 258] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The control of target gene expression by nuclear receptors requires the recruitment of multiple cofactors. However, the exact mechanisms by which nuclear receptor-cofactor interactions result in tissue-specific gene regulation are unclear. Here we characterize a novel tissue-specific coactivator for the androgen receptor (AR), which is identical to a previously reported protein FHL2/DRAL with unknown function. In the adult, FHL2 is expressed in the myocardium of the heart and in the epithelial cells of the prostate, where it colocalizes with the AR in the nucleus. FHL2 contains a strong, autonomous transactivation function and binds specifically to the AR in vitro and in vivo. In an agonist- and AF-2-dependent manner FHL2 selectively increases the transcriptional activity of the AR, but not that of any other nuclear receptor. In addition, the transcription of the prostate-specific AR target gene probasin is coactivated by FHL2. Taken together, our data demonstrate that FHL2 is the first LIM-only coactivator of the AR with a unique tissue-specific expression pattern.
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Affiliation(s)
- J M Müller
- Universitäts-Frauenklinik, Abteilung Frauenheilkunde und Geburtshilfe I, Klinikum der Universität Freiburg, Breisacherstrasse 117, 79106 Freiburg, Germany
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44
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Ma H, Hong H, Huang SM, Irvine RA, Webb P, Kushner PJ, Coetzee GA, Stallcup MR. Multiple signal input and output domains of the 160-kilodalton nuclear receptor coactivator proteins. Mol Cell Biol 1999; 19:6164-73. [PMID: 10454563 PMCID: PMC84548 DOI: 10.1128/mcb.19.9.6164] [Citation(s) in RCA: 183] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/1999] [Accepted: 06/08/1999] [Indexed: 11/20/2022] Open
Abstract
Members of the 160-kDa nuclear receptor coactivator family (p160 coactivators) bind to the conserved AF-2 activation function found in the hormone binding domains of nuclear receptors (NR) and are potent transcriptional coactivators for NRs. Here we report that the C-terminal region of p160 coactivators glucocorticoid receptor interacting protein 1 (GRIP1), steroid receptor coactivator 1 (SRC-1a), and SRC-1e binds the N-terminal AF-1 activation function of the androgen receptor (AR), and p160 coactivators can thereby enhance transcriptional activation by AR. While they all interact efficiently with AR AF-1, these same coactivators have vastly different binding strengths with and coactivator effects on AR AF-2. p160 activation domain AD1, which binds secondary coactivators CREB binding protein (CBP) and p300, was previously implicated as the principal domain for transmitting the activating signal to the transcription machinery. We identified a new highly conserved motif in the AD1 region which is important for CBP/p300 binding. Deletion of AD1 only partially reduced p160 coactivator function, due to signaling through AD2, another activation domain located at the C-terminal end of p160 coactivators. C-terminal coactivator fragments lacking AD1 but containing AD2 and the AR AF-1 binding site served as efficient coactivators for full-length AR and AR AF-1. The two signal input domains (one that binds NR AF-2 domains and one that binds AF-1 domains of some but not all NRs) and the two signal output domains (AD1 and AD2) of p160 coactivators played different relative roles for two different NRs: AR and thyroid hormone receptor.
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Affiliation(s)
- H Ma
- Departments of Pathology, University of Southern California, Los Angeles, California 90033, USA
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45
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Wang Z, Tufts R, Haleem R, Cai X. Genes regulated by androgen in the rat ventral prostate. Proc Natl Acad Sci U S A 1997; 94:12999-3004. [PMID: 9371789 PMCID: PMC24252 DOI: 10.1073/pnas.94.24.12999] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/1997] [Accepted: 09/22/1997] [Indexed: 02/05/2023] Open
Abstract
Genes that are regulated by androgen in the prostate were studied in the rat. Four of the less than 10 genes that are down-regulated by androgen in the ventral prostate of a 7-day castrated rat were identified; their mRNAs decayed with identical kinetics. Twenty-five of the estimated 56 genes that are up-regulated by androgen in the castrated prostate have been isolated. The up-regulated genes fall into two kinetic types. Early genes are significantly up-regulated by 6.5 hr whereas the delayed genes respond mainly after 24 hr from the time of androgen replacement. These androgen-response genes are also regulated in the prostate by castration, indicating that these genes could play important roles in androgen-induced regrowth and/or castration-induced regression of the prostate during hormonal manipulation. A survey of the tissue specificity showed that the androgen-response gene expression program in the prostate is mainly prostate-specific. Total RNA Northern blot analysis detects the expression of about 16 up-regulated genes and 3 down-regulated genes in the prostate only. Four up-regulated genes and one down-regulated gene are regulated by androgen in both the prostate and seminal vesicles but not in other organs. The expression of the remaining androgen-response genes is not limited to the prostate but is only responsive to androgen in the prostate. This survey of the androgen-response gene expression program provides insights into the molecular and cellular mechanisms of androgen action in the prostate.
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Affiliation(s)
- Z Wang
- Department of Urology, Northwestern University Medical School, Chicago, IL 60611, USA.
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46
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Zhang J, Zhang S, Murtha PE, Zhu W, Hou SS, Young CY. Identification of two novel cis-elements in the promoter of the prostate-specific antigen gene that are required to enhance androgen receptor-mediated transactivation. Nucleic Acids Res 1997; 25:3143-50. [PMID: 9224617 PMCID: PMC146840 DOI: 10.1093/nar/25.15.3143] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
A monomeric androgen responsive element (ARE) is not sufficient to mediate significant androgen induction of the prostate-specific antigen (PSA) gene. Co-transfection experiments using a series of 5'deletion fragments of the proximal promoter region of the PSA gene linked to bacterial chloramphenicol acetyltransferase (CAT) as a reporter have identified two motif sequences which are indispensable for androgen receptor (AR)-mediated transactivation of the PSA promoter and have been designated as motifs A and B respectively. Of note, motif B alone has very little independent enhancer activity regardless of the presence or absence of androgen, whereas multi-copies of motif A exert androgenic inducibility for a heterologous promoter independent of the presence of ARE. Nucleotide substitutions in either motif significantly decrease the androgen inducibility and the nuclear protein binding ability. Furthermore, gel band shift experiments consistently demonstrate that nuclear proteins can bind these motifs, and they are non-receptor factors. Our data indicate that these two DNA motifs are novel cis -regulatory elements and exhibit different mechanisms in cooperation with ARE for AR-mediated transactivation.
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Affiliation(s)
- J Zhang
- Department of Urology, Mayo Graduate School, Mayo Clinic/Foundation, Rochester, MN 55905, USA
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47
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Culig Z, Hobisch A, Hittmair A, Cronauer MV, Radmayr C, Bartsch G, Klocker H. Androgen receptor gene mutations in prostate cancer. Implications for disease progression and therapy. Drugs Aging 1997; 10:50-8. [PMID: 9111707 DOI: 10.2165/00002512-199710010-00005] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Recent studies indicate that androgen receptors are present in all histological types of prostatic tumours, in relapsed prostatic carcinomas and in tumour metastases, even those obtained from patients in whom endocrine therapy was unsuccessful. Several research groups have asked whether structurally altered androgen receptors might be present in human prostatic tumours. The first androgen receptor mutation in prostate cancer was detected in the tumour cell line LNCaP. The frequency of androgen receptor mutations in primary tumours of the prostate is relatively low. In contrast, a high frequency of mutations has been reported in bone metastases from patients who did not respond to endocrine therapy. This fact may reflect genetic instability in these late tumour stages. Mutant androgen receptors detected in human prostate cancer cells are 'promiscuous receptors'; that is, they are activated not only by synthetic and testicular androgens, but also by adrenal androgens, products of dihydrotestosterone metabolism, estrogenic and progestagenic steroids, and even by nonsteroidal antiandrogens. Interestingly, the nonsteroidal antiandrogens hydroxyflutamide and nilutamide, but not bicalutamide, have been reported to have agonistic effects at mutant androgen receptors. It is speculated that the existence of androgen receptor mutations may explain, at least in part, the 'antiandrogen withdrawal syndrome': a temporary improvement in a subpopulation of prostate cancer patients following cessation of an antiandrogen from a therapeutic protocol. Further studies on androgen receptor alterations in prostate cancer should focus on metastatic specimens obtained from the late stages of this disease.
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Affiliation(s)
- Z Culig
- Department of Urology, University of Innsbruck, Austria
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48
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Marschke KB, Tan JA, Kupfer SR, Wilson EM, French FS. Specificity of simple hormone response elements in androgen regulated genes. Endocrine 1995; 3:819-25. [PMID: 21153127 DOI: 10.1007/bf02935687] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/22/1995] [Accepted: 05/22/1995] [Indexed: 11/25/2022]
Abstract
Androgen (AR) and glucocorticoid (GR) receptors recognize a family of 15 base pair partial palindromic hormone response elements (HRE). We have studied receptor interactions with several HREs from androgen regulated genes to determine their potential to mediate a selective androgen response. Synthetic oligonucleotides corresponding to the elements were analysed for receptor binding and steroid dependent transcriptional enhancer activities. Each HRE contained the 3' half-site sequence (5'-TGTNCT-3') of the glucocorticoid response element (GRE) consensus sequence. HREs that countained the 5' half-site GRE consensus sequence (5'-A/GGNACA/G-3') had the strongest and-rogen response element (ARE) and GRE activities. In methylation interference assays, AR and GR interacted with identical base contact sites in the response elements. Two elements that deviated from the GRE consensus sequence by a single optimal base in the 5' half, had reduced ARE activity with no significant change in GRE activity and displayed lower binding of AR than GR in mobility shift assays using purified DNA binding domain peptides. Transfections with AR/GR and GR/AR chimeras containing the N-terminal domain of one receptor linked to the DNA-binding and C-terminal domains of the other suggested that N-terminal domain functions of GR also contributed to the greater GRE than ARE activities of the response elements.
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Affiliation(s)
- K B Marschke
- Department of Pediatrics, The University of North Carolina School of Medicine, 27599-7500, Chapel Hill, North Carolina, USA
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Greenberg NM, DeMayo F, Finegold MJ, Medina D, Tilley WD, Aspinall JO, Cunha GR, Donjacour AA, Matusik RJ, Rosen JM. Prostate cancer in a transgenic mouse. Proc Natl Acad Sci U S A 1995; 92:3439-43. [PMID: 7724580 PMCID: PMC42182 DOI: 10.1073/pnas.92.8.3439] [Citation(s) in RCA: 941] [Impact Index Per Article: 32.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
Progress toward understanding the biology of prostate cancer has been slow due to the few animal research models available to study the spectrum of this uniquely human disease. To develop an animal model for prostate cancer, several lines of transgenic mice were generated by using the prostate-specific rat probasin promoter to derive expression of the simian virus 40 large tumor antigen-coding region. Mice expressing high levels of the transgene display progressive forms of prostatic disease that histologically resemble human prostate cancer, ranging from mild intraepithelial hyperplasia to large multinodular malignant neoplasia. Prostate tumors have been detected specifically in the prostate as early as 10 weeks of age. Immunohistochemical analysis of tumor tissue has demonstrated that dorsolateral prostate-specific secretory proteins were confined to well-differentiated ductal epithelial cells adjacent to, or within, the poorly differentiated tumor mass. Prostate tumors in the mice also display elevated levels of nuclear p53 and a decreased heterogeneous pattern of androgen-receptor expression, as observed in advanced human prostate cancer. The establishment of breeding lines of transgenic mice that reproducibly develop prostate cancer provides an animal model system to study the molecular basis of transformation of normal prostatic cells and the factors influencing the progression to metastatic prostate cancer.
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Affiliation(s)
- N M Greenberg
- Department of Cell Biology, Baylor College of Medicine, Houston, TX 77030, USA
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Chamberlain NL, Driver ED, Miesfeld RL. The length and location of CAG trinucleotide repeats in the androgen receptor N-terminal domain affect transactivation function. Nucleic Acids Res 1994; 22:3181-6. [PMID: 8065934 PMCID: PMC310294 DOI: 10.1093/nar/22.15.3181] [Citation(s) in RCA: 757] [Impact Index Per Article: 25.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
Some transcription factors contain stretches of polyglutamine encoded by repeats of the trinucleotide CAG. Expansion of the CAG repeat in the androgen receptor (AR) has been correlated with the incidence and severity of X-linked spinal and bulbar muscular atrophy (Kennedy's disease). In order to understand the relationship of this mutation to AR function, we constructed ARs that varied in the position and size of the polyglutamine tract, and assayed for the abilities of these mutant receptors to bind androgen and to activate transcription of several different AR-responsive reporter genes. Elimination of the tract in both human and rat AR resulted in elevated transcriptional activation activity, strongly suggesting that the presence of the polyglutamine tract is inhibitory to transactivation. Progressive expansion of the CAG repeat in human AR caused a linear decrease of transactivation function. Importantly, expansion of the tract did not completely eliminate AR activity. We postulate that this residual AR activity may be sufficient for development of male primary and secondary sex characteristics, but may fall below a threshold level of activity necessary for normal maintenance of motor neuron function. This functional abnormality may be representative of other genetic diseases that are associated with CAG expansion mutations in open reading frames, such as spinocerebellar ataxia type I and Huntington's disease.
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Affiliation(s)
- N L Chamberlain
- Department of Biochemistry, University of Arizona, Tucson 85724
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