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Katleba K, Lombard AP, Tsamouri MM, Baek HB, Nishida KS, Libertini SJ, Platero AJ, Ma AH, Pan CX, Ghosh PM, Mudryj M. Depletion of androgen receptor low molecular weight isoform reduces bladder tumor cell viability and induces apoptosis. Cancer Lett 2021; 504:49-57. [PMID: 33549708 DOI: 10.1016/j.canlet.2021.01.029] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/20/2020] [Revised: 01/22/2021] [Accepted: 01/29/2021] [Indexed: 01/21/2023]
Abstract
Bladder cancer (BlCa) exhibits a gender disparity where men are three times more likely to develop the malignancy than women suggesting a role for the androgen receptor (AR). Here we report that BlCa cells express low molecular weight (LMW) AR isoforms that are missing the ligand binding domain (LBD). Isoform expression was detected in most BlCa cells, while a few express the full-length AR. Immunofluorescence studies detect AR in the nucleus and cytoplasm, and localization is cell dependent. Cells with nuclear AR expression exhibit reduced viability and increased apoptosis on total AR depletion. A novel AR-LMW variant, AR-v19, that is missing the LBD and contains 15 additional amino acids encoded by intron 3 sequences was detected in most BlCa malignancies. AR-v19 localizes to the nucleus and can transactivate AR-dependent transcription in a dose dependent manner. AR-v19 depletion impairs cell viability and promotes apoptosis in cells that express this variant. Thus, AR splice variant expression is common in BlCa and instrumental in ensuring cell survival. This suggests that targeting AR or AR downstream effectors may be a therapeutic strategy for the treatment of this malignancy.
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Affiliation(s)
- Kimberley Katleba
- Veterans Affairs-Northern California Health Care System, Mather, CA, USA; Department of Medical Microbiology and Immunology, USA
| | - Alan P Lombard
- Veterans Affairs-Northern California Health Care System, Mather, CA, USA; Department of Medical Microbiology and Immunology, USA; Biochemistry, Molecular, Cellular, and Developmental Biology Graduate Group and Biotechnology Program, USA
| | - Maria-Malvina Tsamouri
- Veterans Affairs-Northern California Health Care System, Mather, CA, USA; Department of Urologic Surgery, University of California, 1 Shields Avenue, UC Davis, Davis, CA, 95616, USA
| | - Han Bit Baek
- Veterans Affairs-Northern California Health Care System, Mather, CA, USA; Department of Medical Microbiology and Immunology, USA
| | | | - Stephen J Libertini
- Veterans Affairs-Northern California Health Care System, Mather, CA, USA; Department of Medical Microbiology and Immunology, USA
| | | | - Ai-Hong Ma
- Department of Urologic Surgery, University of California, 1 Shields Avenue, UC Davis, Davis, CA, 95616, USA
| | - Chong-Xian Pan
- Department of Faculty of Medicine, Harvard Medical School, West Roxbury, MA, 02115, USA
| | - Paramita M Ghosh
- Veterans Affairs-Northern California Health Care System, Mather, CA, USA; Department of Urologic Surgery, University of California, 1 Shields Avenue, UC Davis, Davis, CA, 95616, USA
| | - Maria Mudryj
- Veterans Affairs-Northern California Health Care System, Mather, CA, USA; Department of Medical Microbiology and Immunology, USA.
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Siddiqui S, Libertini SJ, Lucas CA, Lombard AP, Baek HB, Nakagawa RM, Nishida KS, Steele TM, Melgoza FU, Borowsky AD, Durbin-Johnson BP, Qi L, Ghosh PM, Mudryj M. The p14ARF tumor suppressor restrains androgen receptor activity and prevents apoptosis in prostate cancer cells. Cancer Lett 2020; 483:12-21. [PMID: 32330514 DOI: 10.1016/j.canlet.2020.03.030] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2019] [Revised: 02/29/2020] [Accepted: 03/28/2020] [Indexed: 02/08/2023]
Abstract
Prostate cancer (PCa) is characterized by a unique dependence on optimal androgen receptor (AR) activity where physiological androgen concentrations induce proliferation but castrate and supraphysiological levels suppress growth. This feature has been exploited in bipolar androgen therapy (BAT) for castrate resistant malignancies. Here, we investigated the role of the tumor suppressor protein p14ARF in maintaining optimal AR activity and the function of the AR itself in regulating p14ARF levels. We used a tumor tissue array of differing stages and grades to define the relationships between these components and identified a strong positive correlation between p14ARF and AR expression. Mechanistic studies utilizing CWR22 xenograft and cell culture models revealed that a decrease in AR reduced p14ARF expression and deregulated E2F factors, which are linked to p14ARF and AR regulation. Chromatin immunoprecipitation studies identified AR binding sites upstream of p14ARF. p14ARF depletion enhanced AR-dependent PSA and TMPRSS2 transcription, hence p14ARF constrains AR activity. However, p14ARF depletion ultimately results in apoptosis. In PCa cells, AR co-ops p14ARF as part of a feedback mechanism to ensure optimal AR activity for maximal prostate cancer cell survival and proliferation.
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Affiliation(s)
- Salma Siddiqui
- Veterans Affairs-Northern California Health Care System, Mather, CA, USA
| | - Stephen J Libertini
- Veterans Affairs-Northern California Health Care System, Mather, CA, USA; Department of Medical Microbiology and Immunology, USA
| | - Christopher A Lucas
- Veterans Affairs-Northern California Health Care System, Mather, CA, USA; Department of Medical Microbiology and Immunology, USA
| | - Alan P Lombard
- Veterans Affairs-Northern California Health Care System, Mather, CA, USA; Department of Medical Microbiology and Immunology, USA
| | - Han Bit Baek
- Veterans Affairs-Northern California Health Care System, Mather, CA, USA; Department of Medical Microbiology and Immunology, USA
| | | | | | - Thomas M Steele
- Veterans Affairs-Northern California Health Care System, Mather, CA, USA; Department of Urologic Surgery, USA
| | - Frank U Melgoza
- Veterans Affairs-Northern California Health Care System, Mather, CA, USA
| | | | | | - LiHong Qi
- Department of Public Health Sciences, University of California Davis, California, USA
| | - Paramita M Ghosh
- Veterans Affairs-Northern California Health Care System, Mather, CA, USA; Department of Urologic Surgery, USA
| | - Maria Mudryj
- Veterans Affairs-Northern California Health Care System, Mather, CA, USA; Department of Medical Microbiology and Immunology, USA.
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Baek HB, Lombard AP, Libertini SJ, Fernandez-Rubio A, Vinall R, Gandour-Edwards R, Nakagawa R, Vidallo K, Nishida K, Siddiqui S, Wettersten H, Landesman Y, Weiss RH, Ghosh PM, Mudryj M. XPO1 inhibition by selinexor induces potent cytotoxicity against high grade bladder malignancies. Oncotarget 2018; 9:34567-34581. [PMID: 30349650 PMCID: PMC6195388 DOI: 10.18632/oncotarget.26179] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2018] [Accepted: 09/15/2018] [Indexed: 12/28/2022] Open
Abstract
Treatment options for high grade urothelial cancers are limited and have remained largely unchanged for several decades. Selinexor (KPT-330), a first in class small molecule that inhibits the nuclear export protein XPO1, has shown efficacy as a single agent treatment for numerous different malignancies, but its efficacy in limiting bladder malignancies has not been tested. In this study we assessed selinexor-dependent cytotoxicity in several bladder tumor cells and report that selinexor effectively reduced XPO1 expression and limited cell viability in a dose dependent manner. The decrease in cell viability was due to an induction of apoptosis and cell cycle arrest. These results were recapitulated in in vivo studies where selinexor decreased tumor growth. Tumors treated with selinexor expressed lower levels of XPO1, cyclin A, cyclin B, and CDK2 and increased levels of RB and CDK inhibitor p27, a result that is consistent with growth arrest. Cells expressing wildtype RB, a potent tumor suppressor that promotes growth arrest and apoptosis, were most susceptible to selinexor. Cell fractionation and immunofluorescence studies showed that selinexor treatment increased nuclear RB levels and mechanistic studies revealed that RB ablation curtailed the response to the drug. Conversely, limiting CDK4/6 dependent RB phosphorylation by palbociclib was additive with selinexor in reducing bladder tumor cell viability, confirming that RB activity has a role in the response to XPO1 inhibition. These results provide a rationale for XPO1 inhibition as a novel strategy for the treatment of bladder malignancies.
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Affiliation(s)
- Han Bit Baek
- Veterans Affairs-Northern California Health Care System, Mather, CA, USA.,Department of Medical Microbiology and Immunology, University of California Davis, Davis, CA, USA
| | - Alan P Lombard
- Veterans Affairs-Northern California Health Care System, Mather, CA, USA.,Department of Medical Microbiology and Immunology, University of California Davis, Davis, CA, USA.,Biochemistry, Molecular, Cellular, and Developmental Biology Graduate Group and Biotechnology Program, University of California Davis, Davis, CA, USA
| | - Stephen J Libertini
- Veterans Affairs-Northern California Health Care System, Mather, CA, USA.,Department of Medical Microbiology and Immunology, University of California Davis, Davis, CA, USA
| | - Aleida Fernandez-Rubio
- Department of Medical Microbiology and Immunology, University of California Davis, Davis, CA, USA
| | - Ruth Vinall
- California Northstate College of Pharmacy, Elk Grove, CA, USA
| | - Regina Gandour-Edwards
- Department of Pathology and Laboratory Medicine, University of California Davis, Sacramento, CA, USA
| | - Rachel Nakagawa
- Department of Medical Microbiology and Immunology, University of California Davis, Davis, CA, USA
| | - Kathleen Vidallo
- Department of Medical Microbiology and Immunology, University of California Davis, Davis, CA, USA
| | - Kristine Nishida
- Department of Medical Microbiology and Immunology, University of California Davis, Davis, CA, USA
| | - Salma Siddiqui
- Veterans Affairs-Northern California Health Care System, Mather, CA, USA
| | - Hiromi Wettersten
- Department of Internal Medicine, University of California Davis, Davis, CA, USA
| | | | - Robert H Weiss
- Veterans Affairs-Northern California Health Care System, Mather, CA, USA.,Department of Internal Medicine, University of California Davis, Davis, CA, USA
| | - Paramita M Ghosh
- Veterans Affairs-Northern California Health Care System, Mather, CA, USA.,Department of Urology, University of California Davis, Sacramento, CA, USA
| | - Maria Mudryj
- Veterans Affairs-Northern California Health Care System, Mather, CA, USA.,Department of Medical Microbiology and Immunology, University of California Davis, Davis, CA, USA
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