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Effects of phosphorylated estrogen receptor alpha on apoptosis in human endometrial epithelial cells. Anat Sci Int 2019; 95:240-250. [PMID: 31823335 DOI: 10.1007/s12565-019-00515-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2019] [Accepted: 11/29/2019] [Indexed: 01/15/2023]
Abstract
It is known that the activities of estrogen receptor α (ERα) can be modulated by epidermal growth factor (EGF) through the phosphatidylinostitol 3-kinase-alpha serine/threonine protein kinase (PI3K-AKT) pathway by phosphorylation. To clarify how ERα functions are regulated in endometrial cells during menstrual cycle, molecules related to phosphorylation of ERα (pERα) were examined. It was found that the expression of phosphorylated AKT on serine 473 (pAKT-Ser473) was increased during the proliferative phase, but decreased in the secretory phase. Although the expression of pAKT on threonine 308 in the proliferative phase was only identified in the wall of arterioles, it was strongly expressed in the cytoplasm of endometrial glandular cells after entering the secretory phase. Further observations revealed that while the expression of pERα-Ser104 was constant, pERα-Ser118 was expressed following a cyclic pattern similar to that of the pAKT-Ser473. Following treatment with specific inhibitors for EGFR-PI3K-AKT pathway, it was found that while the expression of pERα-Ser118 and pERα-Ser167 was inhibited, the induced apoptosis could be antagonized by the addition of estrogen, indicating that a mitochondrial pathway is involved. Therefore, pAKT and pERα or ERα could act cooperatively on coiled arterioles and endometrial cells in order to control menstrual cycle.
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Pan S, Yuan C, Tagmount A, Rudel RA, Ackerman JM, Yaswen P, Vulpe CD, Leitman DC. Parabens and Human Epidermal Growth Factor Receptor Ligand Cross-Talk in Breast Cancer Cells. ENVIRONMENTAL HEALTH PERSPECTIVES 2016; 124:563-9. [PMID: 26502914 PMCID: PMC4858398 DOI: 10.1289/ehp.1409200] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/10/2014] [Accepted: 10/09/2015] [Indexed: 05/21/2023]
Abstract
BACKGROUND Xenoestrogens are synthetic compounds that mimic endogenous estrogens by binding to and activating estrogen receptors. Exposure to estrogens and to some xenoestrogens has been associated with cell proliferation and an increased risk of breast cancer. Despite evidence of estrogenicity, parabens are among the most widely used xenoestrogens in cosmetics and personal-care products and are generally considered safe. However, previous cell-based studies with parabens do not take into account the signaling cross-talk between estrogen receptor α (ERα) and the human epidermal growth factor receptor (HER) family. OBJECTIVES We investigated the hypothesis that the potency of parabens can be increased with HER ligands, such as heregulin (HRG). METHODS The effects of HER ligands on paraben activation of c-Myc expression and cell proliferation were determined by real-time polymerase chain reaction, Western blots, flow cytometry, and chromatin immunoprecipitation assays in ERα- and HER2-positive human BT-474 breast cancer cells. RESULTS Butylparaben (BP) and HRG produced a synergistic increase in c-Myc mRNA and protein levels in BT-474 cells. Estrogen receptor antagonists blocked the synergistic increase in c-Myc protein levels. The combination of BP and HRG also stimulated proliferation of BT-474 cells compared with the effects of BP alone. HRG decreased the dose required for BP-mediated stimulation of c-Myc mRNA expression and cell proliferation. HRG caused the phosphorylation of serine 167 in ERα. BP and HRG produced a synergistic increase in ERα recruitment to the c-Myc gene. CONCLUSION Our results show that HER ligands enhanced the potency of BP to stimulate oncogene expression and breast cancer cell proliferation in vitro via ERα, suggesting that parabens might be active at exposure levels not previously considered toxicologically relevant from studies testing their effects in isolation. CITATION Pan S, Yuan C, Tagmount A, Rudel RA, Ackerman JM, Yaswen P, Vulpe CD, Leitman DC. 2016. Parabens and human epidermal growth factor receptor ligand cross-talk in breast cancer cells. Environ Health Perspect 124:563-569; http://dx.doi.org/10.1289/ehp.1409200.
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Affiliation(s)
- Shawn Pan
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, Berkeley, California, USA
| | - Chaoshen Yuan
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, Berkeley, California, USA
| | - Abderrahmane Tagmount
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, Berkeley, California, USA
| | | | | | - Paul Yaswen
- Life Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California, USA
| | - Chris D. Vulpe
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, Berkeley, California, USA
| | - Dale C. Leitman
- Department of Nutritional Sciences and Toxicology, University of California, Berkeley, Berkeley, California, USA
- Address correspondence to D.C. Leitman, University of California, Berkeley, Department of Nutritional Sciences and Toxicology, 44 Morgan Hall, Berkeley, CA 94720 USA. Telephone: (510) 642-6490. E-mail:
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Williams MD, Nguyen T, Carriere PP, Tilghman SL, Williams C. Protein Kinase CK2 Expression Predicts Relapse Survival in ERα Dependent Breast Cancer, and Modulates ERα Expression in Vitro. INTERNATIONAL JOURNAL OF ENVIRONMENTAL RESEARCH AND PUBLIC HEALTH 2015; 13:ijerph13010036. [PMID: 26703694 PMCID: PMC4730427 DOI: 10.3390/ijerph13010036] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/15/2015] [Revised: 10/09/2015] [Accepted: 10/10/2015] [Indexed: 11/16/2022]
Abstract
The heterotetrameric protein kinase CK2 has been associated with oncogenic transformation, and our previous studies have shown that it may affect estrogenic signaling. Here, we investigate the role of the protein kinase CK2 in regulating ERα (estrogen receptor α) signaling in breast cancer. We determined the correlation of CK2α expression with relapse free breast cancer patient survival utilizing Kaplan Meier Plotter (kmplot.com/analysis/) to mine breast cancer microarrays repositories. Patients were stratified according to ERα status, histological grade, and hormonal therapy. Luciferase reporter assays and flow cytometry were implemented to determine the impact of CK2 inhibition on ERE-mediated gene expression and expression of ERα protein. CK2α expression is associated with shorter relapse free survival among ERα (+) patients with grade 1 or 2 tumors, as well as among those patients receiving hormonal therapy. Biochemical inhibition of CK2 activity results in increased ER-transactivation as well as increased expression among ERα (+) and ERα (−) breast cancer cell lines. These findings suggest that CK2 may contribute to estrogen-independent cell proliferation and breast tumor progression, and may potentially serve as a biomarker and pharmacological target in breast cancer.
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Affiliation(s)
- Marlon D Williams
- College of Pharmacy, Xavier University of Louisiana, 1 Drexel Dr, New Orleans, LA 70125, USA.
| | - Thu Nguyen
- College of Pharmacy, Xavier University of Louisiana, 1 Drexel Dr, New Orleans, LA 70125, USA.
| | - Patrick P Carriere
- College of Pharmacy, Xavier University of Louisiana, 1 Drexel Dr, New Orleans, LA 70125, USA.
| | - Syreeta L Tilghman
- Division of Basic Sciences, College of Pharmacy and Pharmaceutical Sciences, Florida Agricultural & Mechanical University, 1415 S. Martin L. King Jr. Blvd., Tallahassee, FL 32307.
| | - Christopher Williams
- College of Pharmacy, Xavier University of Louisiana, 1 Drexel Dr, New Orleans, LA 70125, USA.
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Anbalagan M, Rowan BG. Estrogen receptor alpha phosphorylation and its functional impact in human breast cancer. Mol Cell Endocrinol 2015; 418 Pt 3:264-72. [PMID: 25597633 DOI: 10.1016/j.mce.2015.01.016] [Citation(s) in RCA: 98] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/08/2014] [Revised: 01/08/2015] [Accepted: 01/12/2015] [Indexed: 02/08/2023]
Abstract
Estrogen receptor α (ERα) is a member of the nuclear receptor superfamily of transcription factors that regulates cell proliferation, differentiation and homeostasis in various tissues. Sustained exposure to estrogen/estradiol (E2) increases the risk of breast, endometrial and ovarian cancers. ERα function is also regulated by phosphorylation through various kinase signaling pathways that will impact various ERα functions including chromatin interaction, coregulator recruitment and gene expression, as well impact breast tumor growth/morphology and breast cancer patient response to endocrine therapy. However, many of the previously characterized ERα phosphorylation sites do not fully explain the impact of receptor phosphorylation on ERα function. This review discusses work from our laboratory toward understanding a role of ERα site-specific phosphorylation in ERα function and breast cancer. The key findings discussed in this review are: (1) the effect of site specific ERα phosphorylation on temporal recruitment of ERα and unique coactivator complexes to specific genes; (2) the impact of stable disruption of ERα S118 and S167 phosphorylation in breast cancer cells on eliciting unique gene expression profiles that culminate in significant effects on breast cancer growth/morphology/migration/invasion; (3) the Src kinase signaling pathway that impacts ERα phosphorylation to alter ERα function; and (4) circadian disruption by light exposure at night leading to elevated ERK1/2 and Src kinase and phosphorylation of ERα, concomitant with tamoxifen resistance in breast tumor models. Results from these studies demonstrate that even changes to single ERα phosphorylation sites can have a profound impact on ERα function in breast cancer. Future work will extend beyond single site phosphorylation analysis toward identification of specific patterns/profiles of ERα phosphorylation under different physiological/pharmacological conditions to understand how common phosphorylation profiles in breast cancer program specific physiological endpoints such as growth, apoptosis, migration/invasion, and endocrine therapy response.
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Affiliation(s)
- Muralidharan Anbalagan
- Department of Structural and Cellular Biology, Tulane University School of Medicine, New Orleans, LA 70112, USA
| | - Brian G Rowan
- Department of Structural and Cellular Biology, Tulane University School of Medicine, New Orleans, LA 70112, USA.
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5
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Koryakina Y, Ta HQ, Gioeli D. Androgen receptor phosphorylation: biological context and functional consequences. Endocr Relat Cancer 2014; 21:T131-45. [PMID: 24424504 PMCID: PMC4437516 DOI: 10.1530/erc-13-0472] [Citation(s) in RCA: 88] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The androgen receptor (AR) is a ligand-regulated transcription factor that belongs to the family of nuclear receptors. In addition to regulation by steroid, the AR is also regulated by post-translational modifications generated by signal transduction pathways. Thus, the AR functions not only as a transcription factor but also as a node that integrates multiple extracellular signals. The AR plays an important role in many diseases, including complete androgen insensitivity syndrome, spinal bulbar muscular atrophy, prostate and breast cancer, etc. In the case of prostate cancer, dependence on AR signaling has been exploited for therapeutic intervention for decades. However, the effectiveness of these therapies is limited in advanced disease due to restoration of AR signaling. Greater understanding of the molecular mechanisms involved in AR action will enable the development of improved therapeutics to treat the wide range of AR-dependent diseases. The AR is subject to regulation by a number of kinases through post-translational modifications on serine, threonine, and tyrosine residues. In this paper, we review the AR phosphorylation sites, the kinases responsible for these phosphorylations, as well as the biological context and the functional consequences of these phosphorylations. Finally, what is known about the state of AR phosphorylation in clinical samples is discussed.
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Affiliation(s)
- Yulia Koryakina
- Department of MicrobiologyImmunology, and Cancer BiologyUVA Cancer CenterUniversity of Virginia, PO Box 800734, Charlottesville, Virginia 22908, USA
| | - Huy Q Ta
- Department of MicrobiologyImmunology, and Cancer BiologyUVA Cancer CenterUniversity of Virginia, PO Box 800734, Charlottesville, Virginia 22908, USA
| | - Daniel Gioeli
- Department of MicrobiologyImmunology, and Cancer BiologyUVA Cancer CenterUniversity of Virginia, PO Box 800734, Charlottesville, Virginia 22908, USADepartment of MicrobiologyImmunology, and Cancer BiologyUVA Cancer CenterUniversity of Virginia, PO Box 800734, Charlottesville, Virginia 22908, USA
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Semba RD, Huang H, Lutty GA, Van Eyk JE, Hart GW. The role of O-GlcNAc signaling in the pathogenesis of diabetic retinopathy. Proteomics Clin Appl 2014; 8:218-31. [PMID: 24550151 DOI: 10.1002/prca.201300076] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2013] [Revised: 09/24/2013] [Accepted: 10/04/2013] [Indexed: 12/14/2022]
Abstract
Diabetic retinopathy is a leading cause of blindness worldwide. Despite laser and surgical treatments, antiangiogenic and other therapies, and strict metabolic control, many patients progress to visual impairment and blindness. New insights are needed into the pathophysiology of diabetic retinopathy in order to develop new methods to improve the detection and treatment of disease and the prevention of blindness. Hyperglycemia and diabetes result in increased flux through the hexosamine biosynthetic pathway, which, in turn, results in increased PTM of Ser/Thr residues of proteins by O-linked β-N-acetylglucosamine (O-GlcNAc). O-GlcNAcylation is involved in regulation of many nuclear and cytoplasmic proteins in a manner similar to protein phosphorylation. Altered O-GlcNAc signaling has been implicated in the pathogenesis of diabetes and may play an important role in the pathogenesis of diabetic retinopathy. The goal of this review is to summarize the biology of the hexosamine biosynthesis pathway and O-GlcNAc signaling, to present the current evidence for the role of O-GlcNAc signaling in diabetes and diabetic retinopathy, and to discuss future directions for research on O-GlcNAc in the pathogenesis of diabetic retinopathy.
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Affiliation(s)
- Richard D Semba
- Wilmer Eye Institute, The Johns Hopkins University School of Medicine, Baltimore, MD, USA
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Lang JD, Berry SM, Powers GL, Beebe DJ, Alarid ET. Hormonally responsive breast cancer cells in a microfluidic co-culture model as a sensor of microenvironmental activity. Integr Biol (Camb) 2013; 5:807-16. [PMID: 23559098 PMCID: PMC3648339 DOI: 10.1039/c3ib20265h] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Breast cancer cell growth and therapeutic response are manipulated extrinsically by microenvironment signals. Despite recognition of the importance of the microenvironment in a variety of tumor processes, predictive measures that incorporate the activity of the surrounding cellular environment are lacking. In contrast, tumor cell biomarkers are well established in the clinic. Expression of Estrogen Receptor-alpha (ERα) is the primary defining feature of hormonally responsive tumors and is the molecular target of therapy in the most commonly diagnosed molecular subtype of breast cancer. While a number of soluble factors have been implicated in ERα activation, the complexity of signaling between the cellular microenvironment and the cancer cell implies multivariate control. The cumulative impact of the microenvironment signaling, which we define as microenvironmental activity, is more difficult to predict than the sum of its parts. Here we tested the impact of an array of microenvironments on ERα signaling utilizing a microfluidic co-culture model. Quantitative immunofluorescence was employed to assess changes in ERα protein levels, combined with gene expression and phosphorylation status, as measures of activation. Analysis of microenvironment-induced growth under the same conditions revealed a previously undescribed correlation between growth and ERα protein down-regulation. These data suggest an expanded utility for the tumor biomarker ERα, in which the combination of dynamic regulation of ERα protein and growth in a breast cancer biosensor cell become a read-out of the microenvironmental activity.
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Affiliation(s)
- Jessica D Lang
- University of Wisconsin-Madison Carbone Comprehensive Cancer Center, Madison, WI 53705, USA
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Huderson BP, Duplessis TT, Williams CC, Seger HC, Marsden CG, Pouey KJ, Hill SM, Rowan BG. Stable inhibition of specific estrogen receptor α (ERα) phosphorylation confers increased growth, migration/invasion, and disruption of estradiol signaling in MCF-7 breast cancer cells. Endocrinology 2012; 153:4144-59. [PMID: 22733972 PMCID: PMC3423624 DOI: 10.1210/en.2011-2001] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Elevated phosphorylation of estrogen receptor α (ERα) at serines 118 (S118) and 167 (S167) is associated with favorable outcome for tamoxifen adjuvant therapy and may serve as surrogate markers for a functional ERα signaling pathway in breast cancer. It is possible that loss of phosphorylation at S118 and/or S167 could disrupt ERα signaling, resulting in aggressive ERα-independent breast cancer cells. To this end, MCF-7 breast cancer cells were stably transfected with an ERα-specific short hairpin RNA that reduced endogenous ERα. The resulting cell line was stably transfected with wild-type ERα (ER-AB cells), or ERα containing serine to alanine mutation at S118 or S167 (S118A cells and S167A cells, respectively). These stable cell lines expressed approximately equivalent ERα compared with parental MCF-7 cells and were evaluated for growth, morphology, migration/invasion, and ERα-regulated gene expression. S118A cells and S167A cells exhibited increased growth and migration/invasion in vitro. Forward- and side-scatter flow cytometry revealed that S167A cells were smaller in size, and both S118A and S167A cells exhibited less cellular complexity. S118A and S167A cells expressed pancytokeratin and membrane localization of β-catenin and did not express vimentin, indicating retention of epithelial lineage markers. Expression of ERα-target genes and other genes regulated by ERα signaling or involved in breast cancer were markedly altered in both S118A and S167A cells. In summary, attenuated phosphorylation of ERα at S118 and S167 significantly affected cellular physiology and behavior in MCF-7 breast cancer cells, resulting in increased growth, migration/invasion, compromised expression of ERα target genes, and markedly altered gene expression patterns.
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Affiliation(s)
- B P Huderson
- Tulane University School of Medicine, Department of Structural and Cellular Biology, 1430 Tulane Avenue SL-49, New Orleans, Louisiana 70112, USA
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Duplessis TT, Williams CC, Hill SM, Rowan BG. Phosphorylation of Estrogen Receptor α at serine 118 directs recruitment of promoter complexes and gene-specific transcription. Endocrinology 2011; 152:2517-26. [PMID: 21505052 PMCID: PMC3100622 DOI: 10.1210/en.2010-1281] [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: 11/19/2022]
Abstract
Phosphorylation of estrogen receptor α (ERα) is important for receptor function, although the role of specific ERα phosphorylation sites in ERα-mediated transcription remains to be fully evaluated. Transcriptional activation by ERα involves dynamic, coordinate interactions with coregulators at promoter enhancer elements to effect gene expression. To determine whether ERα phosphorylation affects recruitment of unique protein complexes at gene-specific promoters, changes in ERα Ser118 phosphorylation were assessed for effects on receptor and coregulator recruitment and transcription of ERα-regulated genes. Chromatin immunoprecipitation assays to measure promoter association found a 17β-estradiol (E2)-dependent recruitment of ERα at 150 min to ERα-regulated promoters, whereas ERα phosphorylated at Ser118 was dissociated from promoters after E2 treatment. Mutation of Ser118 to alanine (S118A) altered unliganded and ligand-induced association of ERα and p160 coregulators with ERα target promoters when compared with wild-type (WT)-ERα transfection. S118A and WT-ERα exhibited a similar level of recruitment to the estrogen response element-driven pS2 promoter and induced pS2 mRNA after E2 treatment. Although WT-ERα was recruited to c-myc and cyclin D1 promoters after E2 treatment and induced mRNA expression, S118A exhibited reduced interaction with c-myc and cyclin D1 promoters, and E2 did not induce c-myc and cyclin D1 mRNA. In addition, S118A resulted in increased recruitment of steroid receptor coactivator-1, glucocorticoid receptor interacting protein-1, and activated in breast cancer-1 to pS2, c-myc, and cyclin D1 irrespective of the presence of E2. Together, these data indicate that site specific phosphorylation of ERα directs gene-specific recruitment of ERα and transcriptional coregulators to ERα target gene promoters.
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Affiliation(s)
- Tamika T Duplessis
- Tulane University School of Medicine, Department of Structural and Cellular Biology, 1430 Tulane Avenue SL-49, New Orleans, Louisiana 70112.
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Bostner J, Skoog L, Fornander T, Nordenskjöld B, Stål O. Estrogen receptor-alpha phosphorylation at serine 305, nuclear p21-activated kinase 1 expression, and response to tamoxifen in postmenopausal breast cancer. Clin Cancer Res 2010; 16:1624-33. [PMID: 20179234 DOI: 10.1158/1078-0432.ccr-09-1733] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
PURPOSE In vitro, p21-activated kinase 1 (Pak1) phosphorylates the serine 305 residue of the estrogen receptor alpha (ERalpha) and influences the response of breast cancer cells to tamoxifen. We investigated the influence of Pak1 and pERalpha(ser305) on breast cancer prognosis and results of tamoxifen therapy. EXPERIMENTAL DESIGN We examined Pak1 and pERalpha(ser305) protein by immunohistochemistry in a series of 912 tumors from node-negative breast cancer patients randomized to tamoxifen or no adjuvant endocrine treatment. RESULTS Cytoplasmic Pak1 correlated to large tumors and ER negativity, whereas nuclear Pak1 and pERalpha(ser305) correlated to small tumors and ER positivity. Nuclear expression of Pak1 and pERalpha(ser305) predicted reduced response to tamoxifen in patients with ERalpha-positive tumors (tamoxifen versus no tamoxifen: hazard ratio (HR), 1.33; 95% confidence interval (95% CI), 0.42-4.2; P = 0.63), whereas patients lacking this combination benefitted significantly from tamoxifen (HR, 0.43; 95% CI, 0.30-0.62; P < 0.0001). Similar nonsignificant trends were detected in analyses of the proteins separately. Pak1 in the cytoplasm was an independent prognostic marker, indicating increased recurrence rate (HR, 1.79; 95% CI, 1.17-2.74; P = 0.0068) and breast cancer mortality (HR, 1.98; 95% CI, 1.14-3.46; P = 0.016) for patients randomized to no adjuvant treatment. CONCLUSION Our results suggest that patients with tumors expressing Pak1 and pERalpha(ser305) in combination are a group in which tamoxifen treatment is insufficient. In addition, the pathway may be of interest as a drug target in breast cancer. Furthermore, the findings support previous studies showing that Pak1 has differential roles in the cytoplasm and the nucleus.
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Affiliation(s)
- Josefine Bostner
- Division of Surgery and Clinical Oncology, Department of Clinical and Experimental Medicine, Faculty of Health Sciences, Linkoping University, Linkoping, Sweden.
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Abstract
Most transcription factors including nuclear receptors (NRs) act as sensors of the extracellular and intracellular compartments. As such, NRs serve as integrating platforms for a variety of stimuli and are targets for Post-translational modifications such as phosphorylations. During the last decade, knowledge of NRs phosphorylation advanced considerably because of the emergence of new technologies. Indeed, the development of a wide range of phosphorylation site databases, high accuracy mass spectrometry, and phospho-specific antibodies allowed the identification of multiple novel phosphorylation sites in NRs. New and improved methods also emerge to connect these data with the downstream consequences of phosphorylation on NRs structure (computational prediction, NMR), intracellular localization (FRAP), interaction with coregulators (proteomics, FRET, FLIM), and affinity for DNA (ChIP, ChIP-seq, FRAP). In the future, such integrated strategies should provide data with a treasure-trove of information about the integration of numerous signaling events by NRs.
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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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Abstract
Steroid receptors (SRs) are hormone-activated transcription factors important for a wide variety of cellular functions. Post-translational modifications of SRs, including phosphorylation, ubiquitination, acetylation, and sumoylation regulate their expression and function. The remarkable number of phosphorylation sites in these receptors and the wide variety of kinases shown to modulate phosphorylation influence the integration between cell-signaling pathways and SR action. These phosphorylation sites have been identified in all of the functional domains with the majority being located within the amino-terminal portions of the receptors. The regulation of function is receptor specific, site specific, and often dependent on the cellular context. Numerous roles for site-specific phosphorylation have been elucidated including sensitivity of hormone response, DNA binding, expression, stability, subcellular localization, dimerization, and protein-protein interactions that can determine the regulation of specific target genes. This review summarizes the current knowledge regarding receptor site-specific phosphorylation and regulation of function. As functional assays become more sophisticated, it is likely that additional roles for phosphorylation in receptor function will be identified.
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Affiliation(s)
- Robert D Ward
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, TX 77030, USA
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Murphy LC, Skliris GP, Rowan BG, Al-Dhaheri M, Williams C, Penner C, Troup S, Begic S, Parisien M, Watson PH. The relevance of phosphorylated forms of estrogen receptor in human breast cancer in vivo. J Steroid Biochem Mol Biol 2009; 114:90-5. [PMID: 19429437 DOI: 10.1016/j.jsbmb.2009.01.017] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/07/2009] [Accepted: 01/21/2009] [Indexed: 10/21/2022]
Abstract
Estrogen receptor (ER)alpha activity is regulated by phosphorylation at several sites. Recently several antibodies specific for individual phosphorylated sites within ERalpha have became available. Validation and use of these antibodies suggests that several forms of phosphorylated ERalpha can be detected in multiple ER+ human breast tumor samples, thus providing relevance for investigating the regulation and function of phosphorylated ERalpha in human breast cancer. Generally, the phosphorylated ERalpha isoforms are associated with parameters that suggest that they are markers of an intact estrogen dependent signaling pathway and better clinical outcome with respect to tamoxifen therapy. Profiling of phosphorylated ERalpha may provide better biomarkers of endocrine therapy response over and above those currently available.
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Affiliation(s)
- Leigh C Murphy
- Manitoba Institute of Cell Biology, University of Manitoba, Winnipeg, Manitoba, Canada.
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Hirahara Y, Matsuda KI, Gao W, Arvanitis DN, Kawata M, Boggs JM. The localization and non-genomic function of the membrane-associated estrogen receptor in oligodendrocytes. Glia 2009; 57:153-65. [PMID: 18709647 DOI: 10.1002/glia.20742] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
There is general acceptance that the estrogen receptor can act as a transcription factor. However, estrogens can also bind to receptors that are located at the plasma membrane and stimulate rapid intracellular signaling processes. We recently showed that a membrane-associated estrogen receptor (mER) is present within myelin and at the oligodendrocyte (OL) plasma membrane. To understand the physiological function of mER in OLs, we investigated its cellular localization and involvement in rapid signaling in CG4 cells and OL primary cultures. An ERalpha was expressed along the lacy network of veins in the membrane sheets and in the perikaryon and nucleus in OLs. ERbeta was located in the nucleus, and to a lesser extent along the veins. The expression of ERalpha and ERbeta in OL membranes was confirmed by Western analysis of isolated membranes. OL membranes mainly had truncated forms of ERalpha, 53 and 50 kDa, in addition to some 65 kDa form, whereas ERbeta was a 54 kDa form. CG4 cells and OLs were pulsed with 17alpha- and 17beta-estradiol for various times and the total lysates were analyzed for phosphorylated kinases. Both 17alpha- and 17beta-estradiol elicited rapid phosphorylation of p42/44MAPK, Akt, and GSK-3beta within 8 min. This rapid signaling is consistent with estradiol ligation of a membrane form of ER. Since 17alpha-estradiol is produced at higher concentrations than 17beta-estradiol in the brain of both sexes, signaling via 17alpha-estradiol-liganded mER may have an important function in OLs.
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Affiliation(s)
- Yukie Hirahara
- Division of Molecular Structure and Function, Research Institute, Hospital for Sick Children, Toronto, Ontario, Canada
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Torra IP, Staverosky JA, Ha S, Logan SK, Garabedian MJ. Development of phosphorylation site-specific antibodies to nuclear receptors. Methods Mol Biol 2009; 505:221-235. [PMID: 19117148 DOI: 10.1007/978-1-60327-575-0_13] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Protein phosphorylation is a versatile posttranslational modification that can regulate nuclear receptor function. Although the precise role of receptor phosphorylation is not fully understood, it appears that it functions to direct or refine receptor activity in response to particular physiological requirements. Identifying and characterizing specific nuclear receptor phosphorylation sites is an important step in elucidating the role(s) receptor phosphorylation plays in function. Although traditional methods of metabolic labeling and in vitro protein phosphorylation have been informative, receptor phosphorylation site-specific antibodies are simple and reliable tools to study receptor phosphorylation. This chapter will discuss how to develop nuclear receptor phosphorylation site-specific antibodies to elucidate function.
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Affiliation(s)
- Inés Pineda Torra
- Department of Microbiology, NYU School of Medicine, New York, NY, USA
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17
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Immunohistochemical validation of multiple phospho-specific epitopes for estrogen receptor alpha (ERalpha) in tissue microarrays of ERalpha positive human breast carcinomas. Breast Cancer Res Treat 2008; 118:443-53. [PMID: 19104930 DOI: 10.1007/s10549-008-0267-z] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2008] [Accepted: 12/04/2008] [Indexed: 10/21/2022]
Abstract
Estrogen receptor alpha (ERalpha) activity is regulated by phosphorylation at several sites. Recently several antibodies specific for individual phosphorylated sites within ERalpha have became available. Such antibodies potentially provide invaluable tools to gain insight into the relevance in vivo of phosphorylated ERalpha in human breast tumors. However, validation of these antibodies for immunohistochemistry in particular is necessary in the first instance. In this study we have investigated the usefulness of several antibodies generated to specific phosphorylated sites within ERalpha for immunohistochemistry of formalin-fixed, paraffin-embedded human breast cancer biopsy samples. As well, these data demonstrate for the first time, the detection of multiple phosphorylated ERalpha forms in breast cancer (P-S104/106-ERalpha, P-S118-ERalpha, P-S167-ERalpha, P-S282-ERalpha, P-S294-ERalpha, P-T311-ERalpha, and P-S559-ERalpha) suggesting the possibility that profiling of phosphorylated ERalpha isoforms might be useful in selecting subgroups of breast cancer patients that would benefit from endocrine therapy.
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Weigel NL, Moore NL. Steroid receptor phosphorylation: a key modulator of multiple receptor functions. Mol Endocrinol 2007; 21:2311-9. [PMID: 17536004 DOI: 10.1210/me.2007-0101] [Citation(s) in RCA: 132] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
Abstract
Steroid receptors are hormone-activated transcription factors, the expression and activities of which are also highly dependent upon posttranslational modifications including phosphorylation. The remarkable number of phosphorylation sites in these receptors and the wide variety of kinases participating in their phosphorylation facilitate integration between cell-signaling pathways and steroid receptor action. Sites have been identified in all of the functional domains although the sites are predominantly in the amino-terminal portions of the receptors. Regulation of function is receptor specific, site specific, and often dependent upon activation of a specific cell-signaling pathway. This complexity explains, in part, the early difficulties in identifying roles for phosphorylation in receptor function. With increased availability of phosphorylation site-specific antibodies and better means to measure receptor activities, numerous roles for site-specific phosphorylation have been identified including sensitivity of response to hormone, DNA binding, expression, stability, subcellular localization, and protein-protein interactions that determine the level of regulation of specific target genes. This review summarizes current knowledge regarding receptor phosphorylation and regulation of function. As functional assays become more sophisticated, it is likely that additional roles for phosphorylation in receptor function will be identified.
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Affiliation(s)
- Nancy L Weigel
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas 77030, USA.
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Weigel NL, Moore NL. Kinases and protein phosphorylation as regulators of steroid hormone action. NUCLEAR RECEPTOR SIGNALING 2007; 5:e005. [PMID: 17525795 PMCID: PMC1876600 DOI: 10.1621/nrs.05005] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/08/2007] [Accepted: 04/27/2007] [Indexed: 11/20/2022]
Abstract
Although the primary signal for the activation of steroid hormone receptors is binding of hormone, there is increasing evidence that the activities of cell signaling pathways and the phosphorylation status of these transcription factors and their coregulators determine the overall response to the hormone. In some cases, enhanced cell signaling is sufficient to cause activation of receptors in medium depleted of steroids. Steroid receptors are targets for multiple kinases. Many of the phosphorylation sites contain Ser/Thr-Pro motifs implicating proline-directed kinases such as the cyclin-dependent kinases and the mitogen-activated kinases (MAPK) in receptor phosphorylation. Although some sites are constitutively phosphorylated, others are phosphorylated in response to hormone. Still others are only phosphorylated in response to specific cell signaling pathways. Phosphorylation of specific sites has been implicated not only in overall transcriptional activity, but also in nuclear localization, protein stability, and DNA binding. The studies of the roles of phosphorylation in coregulator function are more limited, but it is now well established that many of them are highly phosphorylated and that phosphorylation regulates their function. There is good evidence that some of the phosphorylation sites in the receptors and coregulators are targets of multiple signaling pathways. Individual sites have been associated both with functions that enhance the activity of the receptor, as well as with functions that inhibit activity. Thus, the specific combinations of phosphorylations of the steroid receptor combined with the expression levels and phosphorylation status of coregulators will determine the genes regulated and the biological response.
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Affiliation(s)
- Nancy L Weigel
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas, USA.
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Márquez-Garbán DC, Chen HW, Fishbein MC, Goodglick L, Pietras RJ. Estrogen receptor signaling pathways in human non-small cell lung cancer. Steroids 2007; 72:135-43. [PMID: 17276470 PMCID: PMC6662925 DOI: 10.1016/j.steroids.2006.11.019] [Citation(s) in RCA: 170] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/09/2006] [Accepted: 11/14/2006] [Indexed: 12/23/2022]
Abstract
Lung cancer is the most common cause of cancer mortality in male and female patients in the US. The etiology of non-small cell lung cancer (NSCLC) is not fully defined, but new data suggest that estrogens and growth factors promote tumor progression. In this work, we confirm that estrogen receptors (ER), both ERalpha and ERbeta, occur in significant proportions of archival NSCLC specimens from the clinic, with receptor expression in tumor cell nuclei and in extranuclear sites. Further, ERalpha in tumor nuclei was present in activated forms as assessed by detection of ER phosphorylation at serines-118 and -167, residues commonly modulated by growth factor receptor as well as steroid signaling. In experiments using small interfering RNA (siRNA) constructs, we find that suppressing expression of either ERalpha or ERbeta elicits a significant reduction in NSCLC cell proliferation in vitro. Estrogen signaling in NSCLC cells may also include steroid receptor coactivators (SRC), as SRC-3 and MNAR/PELP1 are both expressed in several lung cell lines, and both EGF and estradiol elicit serine phosphorylation of SRC-3 in vitro. EGFR and ER also cooperate in promoting early activation of p42/p44 MAP kinase in NSCLC cells. To assess new strategies to block NSCLC growth, we used Faslodex alone and with erlotinib, an EGFR kinase inhibitor. The drug tandem elicited enhanced blockade of the growth of NSCLC xenografts in vivo, and antitumor activity exceeded that of either agent given alone. The potential for use of antiestrogens alone and with growth factor receptor antagonists is now being pursued further in clinical trials.
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Affiliation(s)
- Diana C. Márquez-Garbán
- Department of Medicine, Division of Hematology-Oncology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095-1678, USA
- Jonsson Comprehensive Cancer Center, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095-1678, USA
| | - Hsiao-Wang Chen
- Department of Medicine, Division of Hematology-Oncology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095-1678, USA
| | - Michael C. Fishbein
- Department of Pahology and Laboratory Medicine, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095-1678, USA
- Jonsson Comprehensive Cancer Center, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095-1678, USA
- Corresponding Author: Richard J. Pietras, MD, PhD, UCLA School of Medicine, Department of Medicine-Hematology/Oncology, 10833 Le Conte Ave., 11-934 Factor Bldg. Los Angeles, CA 90095-1668, USA, , Tel: (310) 825-9769; Fax: (310) 825-2493
| | - Lee Goodglick
- Department of Pahology and Laboratory Medicine, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095-1678, USA
- Jonsson Comprehensive Cancer Center, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095-1678, USA
| | - Richard J. Pietras
- Department of Medicine, Division of Hematology-Oncology, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095-1678, USA
- Jonsson Comprehensive Cancer Center, David Geffen School of Medicine at UCLA, Los Angeles, CA 90095-1678, USA
- Corresponding Author: Richard J. Pietras, MD, PhD, UCLA School of Medicine, Department of Medicine-Hematology/Oncology, 10833 Le Conte Ave., 11-934 Factor Bldg. Los Angeles, CA 90095-1668, USA, , Tel: (310) 825-9769; Fax: (310) 825-2493
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Murphy LC, Weitsman GE, Skliris GP, Teh EM, Li L, Peng B, Davie JR, Ung K, Niu YL, Troup S, Tomes L, Watson PH. Potential role of estrogen receptor alpha (ERalpha) phosphorylated at Serine118 in human breast cancer in vivo. J Steroid Biochem Mol Biol 2006; 102:139-46. [PMID: 17092701 DOI: 10.1016/j.jsbmb.2006.09.021] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
Post-translational modifications of proteins are known to be important in protein activity and ERalpha is known to be phosphorylated at multiple sites within the protein. The exact function of site-specific phosphorylation in ERalpha is unknown, although several hypotheses have been developed using site-directed mutagenesis and cell culture models. Targeting the ERalpha at the level of such post-translational modification pathways would be a new and exciting approach to endocrine therapy in breast cancer, but adequate knowledge is lacking with regard to the relevance of site-specific phosphorylation in ERalpha in human breast cancer in vivo. Recently, antibodies to P-Serine(118)-ERalpha and P-Serine(167)-ERalpha, two major sites of phosphorylation in ERalpha, have become available and some in vivo data are now available to complement studies in cells in culture. However, the in vivo data are somewhat contradictory and limited by the small cohorts used and the lack of standard well-characterized reagents and protocols.
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Affiliation(s)
- Leigh C Murphy
- Manitoba Institute of Cell Biology, University of Manitoba, Winnipeg, Man. R3E 0V9, Canada.
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