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Anbalagan M, Sheng M, Fleischer B, Zhang Y, Gao Y, Hoang V, Matossian M, Burks HE, Burow ME, Collins-Burow BM, Hangauer D, Rowan BG. Dual Src Kinase/Pretubulin Inhibitor KX-01, Sensitizes ERα-negative Breast Cancers to Tamoxifen through ERα Reexpression. Mol Cancer Res 2017; 15:1491-1502. [PMID: 28751463 DOI: 10.1158/1541-7786.mcr-16-0297-t] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Revised: 02/22/2017] [Accepted: 07/19/2017] [Indexed: 12/20/2022]
Abstract
Unlike breast cancer that is positive for estrogen receptor-α (ERα), there are no targeted therapies for triple-negative breast cancer (TNBC). ERα is silenced in TNBC through epigenetic changes including DNA methylation and histone acetylation. Restoring ERα expression in TNBC may sensitize patients to endocrine therapy. Expression of c-Src and ERα are inversely correlated in breast cancer suggesting that c-Src inhibition may lead to reexpression of ERα in TNBC. KX-01 is a peptide substrate-targeted Src/pretubulin inhibitor in clinical trials for solid tumors. KX-01 (1 mg/kg body weight-twice daily) inhibited growth of tamoxifen-resistant MDA-MB-231 and MDA-MB-157 TNBC xenografts in nude mice that was correlated with Src kinase inhibition. KX-01 also increased ERα mRNA and protein, as well as increased the ERα targets progesterone receptor (PR), pS2 (TFF1), cyclin D1 (CCND1), and c-myc (MYC) in MDA-MB-231 and MDA-MB-468, but not MDA-MB-157 xenografts. MDA-MB-231 and MDA-MB-468 tumors exhibited reduction in mesenchymal markers (vimentin, β-catenin) and increase in epithelial marker (E-cadherin) suggesting mesenchymal-to-epithelial transition (MET). KX-01 sensitized MDA-MB-231 and MDA-MB-468 tumors to tamoxifen growth inhibition and tamoxifen repression of the ERα targets pS2, cyclin D1, and c-myc. Chromatin immunoprecipitation (ChIP) of the ERα promoter in KX-01-treated tumors demonstrated enrichment of active transcription marks (acetyl-H3, acetyl-H3Lys9), dissociation of HDAC1, and recruitment of RNA polymerase II. Methylation-specific PCR and bisulfite sequencing demonstrated no alteration in ERα promoter methylation by KX-01. These data demonstrate that in addition to Src kinase inhibition, peptidomimetic KX-01 restores ERα expression in TNBC through changes in histone acetylation that sensitize tumors to tamoxifen.Implications: Src kinase/pretubulin inhibitor KX-01 restores functional ERα expression in ERα- breast tumors, a novel treatment strategy to treat triple-negative breast cancer. Mol Cancer Res; 15(11); 1491-502. ©2017 AACR.
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Affiliation(s)
- Muralidharan Anbalagan
- Department of Structural and Cellular Biology, Tulane University School of Medicine, New Orleans, Louisiana
| | - Mei Sheng
- Department of Structural and Cellular Biology, Tulane University School of Medicine, New Orleans, Louisiana
| | - Brian Fleischer
- Department of Structural and Cellular Biology, Tulane University School of Medicine, New Orleans, Louisiana
| | - Yifang Zhang
- Department of Structural and Cellular Biology, Tulane University School of Medicine, New Orleans, Louisiana.,Department of Obstetrics and Gynecology, Affiliated Hospital of Taishan Medical University, Taishan, Shandong, China
| | - Yuanjun Gao
- Department of Structural and Cellular Biology, Tulane University School of Medicine, New Orleans, Louisiana.,Department of Gastroenterology, Taihe Hospital, Hubei University of Medicine, Hubei, China
| | - Van Hoang
- Department of Medicine, Section of Hematology and Medical Oncology, Tulane University School of Medicine, New Orleans, Louisiana
| | - Margarite Matossian
- Department of Medicine, Section of Hematology and Medical Oncology, Tulane University School of Medicine, New Orleans, Louisiana
| | - Hope E Burks
- Department of Medicine, Section of Hematology and Medical Oncology, Tulane University School of Medicine, New Orleans, Louisiana
| | - Matthew E Burow
- Department of Medicine, Section of Hematology and Medical Oncology, Tulane University School of Medicine, New Orleans, Louisiana
| | - Bridgette M Collins-Burow
- Department of Medicine, Section of Hematology and Medical Oncology, Tulane University School of Medicine, New Orleans, Louisiana
| | - David Hangauer
- Athenex Pharmaceuticals LLC, New York State Center of Excellence in Bioinformatics and Life Sciences, Buffalo, New York
| | - Brian G Rowan
- Department of Structural and Cellular Biology, Tulane University School of Medicine, New Orleans, Louisiana.
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Williams CC, Basu A, El-Gharbawy A, Carrier LM, Smith CL, Rowan BG. Identification of four novel phosphorylation sites in estrogen receptor alpha: impact on receptor-dependent gene expression and phosphorylation by protein kinase CK2. BMC BIOCHEMISTRY 2009; 10:36. [PMID: 20043841 PMCID: PMC2811108 DOI: 10.1186/1471-2091-10-36] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/22/2009] [Accepted: 12/31/2009] [Indexed: 12/13/2022]
Abstract
Background Estrogen receptor α (ERα) phosphorylation is important for estrogen-dependent transcription of ER-dependent genes, ligand-independent receptor activation and endocrine therapy response in breast cancer. However ERα phosphorylation at the previously identified sites does not fully account for these receptor functions. To determine if additional ERα phosphorylation sites exist, COS-1 cells expressing human ERα were labeled with [32P]H3PO4 in vivo and ERα tryptic phosphopeptides were isolated to identify phosphorylation sites. Results Previously uncharacterized phosphorylation sites at serines 46/47, 282, 294, and 559 were identified by manual Edman degradation and phosphoamino acid analysis and confirmed by mutagenesis and phospho-specific antibodies. Antibodies detected phosphorylation of endogenous ERα in MCF-7, MCF-7-LCC2, and Ishikawa cancer cell lines by immunoblot. Mutation of Ser-282 and Ser-559 to alanine (S282A, S559A) resulted in ligand independent activation of ERα as determined by both ERE-driven reporter gene assays and endogenous pS2 gene expression in transiently transfected HeLa cells. Mutation of Ser-46/47 or Ser-294 to alanine markedly reduced estradiol dependent reporter activation. Additionally protein kinase CK2 was identified as a kinase that phosphorylated ERα at S282 and S559 using motif analysis, in vitro kinase assays, and incubation of cells with CK2 kinase inhibitor. Conclusion These novel ERα phosphorylation sites represent new means for modulation of ERα activity. S559 represents the first phosphorylation site identified in the extreme C-terminus (F domain) of a steroid receptor.
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Affiliation(s)
- Christopher C Williams
- 1Division of Basic Pharmaceutical Sciences, College of Pharmacy, Xavier University of Louisiana, New Orleans, LA, USA.
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Narayanan R, Coss CC, Yepuru M, Kearbey JD, Miller DD, Dalton JT. Steroidal androgens and nonsteroidal, tissue-selective androgen receptor modulator, S-22, regulate androgen receptor function through distinct genomic and nongenomic signaling pathways. Mol Endocrinol 2008; 22:2448-65. [PMID: 18801930 DOI: 10.1210/me.2008-0160] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Androgen receptor (AR) ligands are important for the development and function of several tissues and organs. However, the poor oral bioavailability, pharmacokinetic properties, and receptor cross-reactivity of testosterone, coupled with side effects, place limits on its clinical use. Selective AR modulators (SARMs) elicit anabolic effects in muscle and bone, sparing reproductive organs like the prostate. However, molecular mechanisms underlying the tissue selectivity remain ambiguous. We performed a variety of in vitro studies to compare and define the molecular mechanisms of an aryl propionamide SARM, S-22, as compared with dihydrotestosterone (DHT). Studies indicated that S-22 increased levator ani muscle weight but decreased the size of prostate in rats. Analysis of the upstream intracellular signaling events indicated that S-22 and DHT mediated their actions through distinct pathways. Modulation of these pathways altered the recruitment of AR and its cofactors to the PSA enhancer in a ligand-dependent fashion. In addition, S-22 induced Xenopus laevis oocyte maturation and rapid phosphorylation of several kinases, through pathways distinct from steroids. These studies reveal novel differences in the molecular mechanisms by which S-22, a nonsteroidal SARM, and DHT mediate their pharmacological effects.
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Affiliation(s)
- Ramesh Narayanan
- Preclinical Research and Development, GTx, Inc., 3 North Dunlap Street, Memphis, Tennessee 38163, USA
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Al-Dhaheri MH, Rowan BG. Application of phosphorylation site-specific antibodies to measure nuclear receptor signaling: characterization of novel phosphoantibodies for estrogen receptor alpha. NUCLEAR RECEPTOR SIGNALING 2006; 4:e007. [PMID: 16741565 PMCID: PMC1472668 DOI: 10.1621/nrs.04007] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/10/2005] [Accepted: 02/21/2006] [Indexed: 01/22/2023]
Abstract
An understanding of posttranslational events in nuclear receptor signaling is crucial for drug design and clinical therapeutic strategies. Phosphorylation is a well-characterized posttranslational modification that regulates subcellular localization and function of nuclear receptors and coregulators. Although the role of single phosphorylation sites in nuclear receptor function has been described, the contribution of combinations of multiple phosphorylation sites to receptor function remains unclear. The development of phosphoantibodies to each phosphorylation site in a nuclear receptor is a powerful tool to address the role of phosphorylation in multiply phosphorylated receptors. However, phosphoantibodies must be rigorously validated prior to use. This review describes the general methodology for design, characterization and validation of phosphoantibodies using the example of eight phosphoantibodies raised against phosphorylation sites in estrogen receptor alpha (ERalpha).
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