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Abdel-Hafiz HA, Horwitz KB. Post-translational modifications of the progesterone receptors. J Steroid Biochem Mol Biol 2014; 140:80-9. [PMID: 24333793 PMCID: PMC3923415 DOI: 10.1016/j.jsbmb.2013.12.008] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/22/2013] [Revised: 11/30/2013] [Accepted: 12/02/2013] [Indexed: 01/21/2023]
Abstract
Progesterone plays a key role in the development, differentiation and maintenance of female reproductive tissues and has multiple non-reproductive neural functions. Depending on the cell and tissue, the hormonal environment, growth conditions and the developmental stage, progesterone can either stimulate cell growth or inhibit it while promoting differentiation. Progesterone receptors (PRs) belong to the steroid hormone receptor superfamily of ligand-dependent transcription factors. PR proteins are subject to extensive post-translational modifications that include phosphorylation, acetylation, ubiquitination and SUMOylation. The interplay among these modifications is complex with alteration of the receptors by one factor influencing the impact of another. Control over these modifications is species-, tissue- and cell-specific. They in turn regulate multiple functions including PR stability, their subcellular localization, protein-protein interactions and transcriptional activity. These complexities may explain how tissue- and gene-specific differences in regulation are achieved in the same organism, by the same receptor protein and hormone. Here we review current knowledge of PR post-translational modifications and discuss how these may influence receptor function focusing on human breast cancer cells. There is much left to be learned. However, our understanding of this may help to identify therapeutic agents that target PR activity in tissue-specific, even gene-specific ways.
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Affiliation(s)
- Hany A Abdel-Hafiz
- Division of Endocrinology, Department of Medicine, Anschutz Medical Campus, University of Colorado Denver, Aurora, CO 80045, USA.
| | - Kathryn B Horwitz
- Division of Endocrinology, Department of Medicine, Anschutz Medical Campus, University of Colorado Denver, Aurora, CO 80045, USA; Department of Pathology, Anschutz Medical Campus, University of Colorado Denver, Aurora, CO 80045, USA
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Desaulniers D, Leingartner K, Zacharewski T, Foster WG. Optimization of an MCF7-E3 Cell Proliferation Assay and Effects of Environmental Pollutants and Industrial Chemicals. Toxicol In Vitro 2012; 12:409-22. [PMID: 20654424 DOI: 10.1016/s0887-2333(98)00004-6] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/17/1997] [Indexed: 10/18/2022]
Abstract
Environmental contaminants might adversely affect human health by acting as endocrine disruptors and thus need to be identified. Our objective was to optimize the MCF7 cell proliferation assay to screen industrial chemicals for potential oestrogenic effects. Growth conditions, performance of the clone E3 and WT-MCF7 cells and five methods to derive proliferation indices were compared. The E3 cells were further characterized by testing the effects of transforming growth factorbeta (TGFbeta), epidermal growth factor (EGF), insulin, testosterone, the anti-oestrogen ICI 164,384 (ICI) and environmental contaminants with known oestrogenic potential. Industrial chemicals with unknown oestrogenic effects were then tested. As expected, induction of proliferation by estradiol-17beta (E2) was greater and less variable using the clone E3. To generate proliferation indices, the alamarBlue assay had a sensitivity comparable to that of [(3)H]thymidine incorporation ((3)H-TI). The E3 cells were not responsive to EGF (0-100 ng/ml) or insulin (0-313 ng/ml) but their proliferation was decreased (P<0.05) by TGFbeta (45 ng/ml) and testosterone (10(-8)m), which might be typical of highly oestrogen-responsive MCF7 cells. ICI (5x10(-7)m) inhibited the proliferative effects of 10(-10)m E2 and that of 10(-6)m 4-tert-octylphenol (Op) but not the proliferative effect of 10(-5)m Op, suggesting displacement of ICI by Op or induction of oestrogen-receptor independent proliferation. N-oxydiethylene-2-benzothiazole sulfenamide (OBTS) altered (3)H-TI in the MCF7 cells, although not in a dose related manner. OBTS did not induce uterotrophic effects in immature female rats, or any response in a human oestrogen chimeric receptor/reporter gene assay, suggesting that its effects were not mediated through the binding of the oestrogen-receptor. Seven other industrial chemicals were tested and had no effects. In conclusion, the MCF7 cell proliferation assay is one screening tool that permits identification of chemicals with oestrogenic potential which thus require further testing.
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Affiliation(s)
- D Desaulniers
- Reproductive Toxicology Section, Environmental and Occupational Toxicology Division, Bureau of Chemical Hazards, Environmental Health Directorate, Health Protection Branch, Department of Health, Ottawa, Ontario, Canada, K1A 0L2
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Abdel-Hafiz HA, Horwitz KB. Control of progesterone receptor transcriptional synergy by SUMOylation and deSUMOylation. BMC Mol Biol 2012; 13:10. [PMID: 22439847 PMCID: PMC3373386 DOI: 10.1186/1471-2199-13-10] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2011] [Accepted: 03/22/2012] [Indexed: 12/02/2022] Open
Abstract
Background Covalent modification of nuclear receptors by the Small Ubiquitin-like Modifier (SUMO) is dynamically regulated by competing conjugation/deconjugation steps that modulate their overall transcriptional activity. SUMO conjugation of progesterone receptors (PRs) at the N-terminal lysine (K) 388 residue of PR-B is hormone-dependent and suppresses PR-dependent transcription. Mutation of the SUMOylation motif promotes transcriptional synergy. Results The present studies address mechanisms underlying this transcriptional synergy by using SUMOylation deficient PR mutants and PR specifically deSUMOylated by Sentrin-specific proteases (SENPs). We show that deSUMOylation of a small pool of receptors by catalytically competent SENPs globally modulates the cooperativity-driven transcriptional synergy between PR observed on exogenous promoters containing at least two progesterone-response elements (PRE2). This occurs in part by raising PR sensitivity to ligands. The C-terminal ligand binding domain of PR is required for the transcriptional stimulatory effects of N-terminal deSUMOylation, but neither a functional PR dimerization interface, nor a DNA binding domain exhibiting PR specificity, are required. Conclusion We conclude that direct and reversible SUMOylation of a minor PR protein subpopulation tightly controls the overall transcriptional activity of the receptors at complex synthetic promoters. Transcriptional synergism controlled by SENP-dependent PR deSUMOylation is dissociable from MAPK-catalyzed receptor phosphorylation, from SRC-1 coactivation and from recruitment of histone deacetylases to promoters. This will provide more information for targeting PR as a part of hormonal therapy of breast cancer. Taken together, these data demonstrate that the SUMOylation/deSUMOylation pathway is an interesting target for therapeutic treatment of breast cancer.
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Affiliation(s)
- Hany A Abdel-Hafiz
- Division of Endocrinology, Department of Medicine, Anschutz Medical Campus, University of Colorado, Aurora, CO 80045, USA.
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Masri S, Liu Z, Phung S, Wang E, Yuan YC, Chen S. The role of microRNA-128a in regulating TGFbeta signaling in letrozole-resistant breast cancer cells. Breast Cancer Res Treat 2010; 124:89-99. [PMID: 20054641 DOI: 10.1007/s10549-009-0716-3] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2009] [Accepted: 12/23/2009] [Indexed: 12/19/2022]
Abstract
Resistance to endocrine therapy agents has presented a clinical obstacle in the treatment of hormone-dependent breast cancer. Our laboratory has initiated a study of microRNA regulation of signaling pathways that may result in breast cancer progression on aromatase inhibitors (AI). Microarray analysis of hormone refractory cell lines identified 115 differentially regulated microRNAs, of which 49 microRNAs were believed to be hormone-responsive. A group of microRNAs were inversely expressed in the AI-resistant lines versus LTEDaro and tamoxifen-resistant. We focused our work on hsa-miR-128a which was hormone-responsive and selectively up-regulated in the letrozole-resistant cell lines. Human miR-128a was predicted to target the TGFβ signaling pathway and indeed sensitivity to TGFβ was compromised in the letrozole-resistant cells, as compared to parental MCF-7aro. Human miR-128a was shown to negatively target TGFβRI protein expression by binding to the 3'UTR region of the gene. Inhibition of endogenous miR-128a resulted in resensitization of the letrozole-resistant lines to TGFβ growth inhibitory effects. These data suggest that the hormone-responsive miR-128a can modulate TGFβ signaling and survival of the letrozole-resistant cell lines. To our knowledge, this is the first study to address the role of microRNA regulation as well as TGFβ signaling in AI-resistant breast cancer cell lines. We believe that in addition to estrogen-modulation of gene expression, hormone-regulated microRNAs may provide an additional level of post-transcriptional regulation of signaling pathways critically involved in breast cancer progression and AI-resistance.
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Affiliation(s)
- Selma Masri
- Division of Tumor Cell Biology, Beckman Research Institute of the City of Hope, 1500 E Duarte Road, Duarte, CA 91010, USA
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miR-22 inhibits estrogen signaling by directly targeting the estrogen receptor alpha mRNA. Mol Cell Biol 2009; 29:3783-90. [PMID: 19414598 DOI: 10.1128/mcb.01875-08] [Citation(s) in RCA: 203] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Estrogen receptor alpha (ER alpha) is a ligand-regulated transcription factor with a broad range of physiological functions and one of the most important classifiers in breast cancer. MicroRNAs (miRNAs) are small noncoding RNAs that have emerged as important regulators of gene expression in a plethora of physiological and pathological processes. Upon binding the 3' untranslated region (UTR) of target mRNAs, miRNAs typically reduce their stability and/or translation. The ER alpha mRNA has a long 3' UTR of about 4.3 kb which has been reported to reduce mRNA stability and which bears evolutionarily conserved miRNA target sites, suggesting that it might be regulated by miRNAs. We have performed a comprehensive and systematic assessment of the regulatory role of all miRNAs that are predicted to target the 3' UTR of the ER alpha mRNA. We found that miR-22 represses ER alpha expression most strongly and by directly targeting the ER alpha mRNA 3' UTR. Of the three predicted miR-22 target sites in the 3' UTR, the evolutionarily conserved one is the primary target. miR-22 overexpression leads to a reduction of ER alpha levels, at least in part by inducing mRNA degradation, and compromises estrogen signaling, as exemplified by its inhibitory impact on the ER alpha-dependent proliferation of breast cancer cells.
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Abdel-Hafiz H, Dudevoir ML, Horwitz KB. Mechanisms underlying the control of progesterone receptor transcriptional activity by SUMOylation. J Biol Chem 2009; 284:9099-108. [PMID: 19211567 DOI: 10.1074/jbc.m805226200] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Posttranslational modification by small ubiquitin-like modifier (SUMO) is a major regulator of transcription. We previously showed that progesterone receptors (PR) have a single consensus psiKXE SUMO-conjugation motif centered at Lys-388 in the N-terminal domain of PR-B and a homologous site of PR-A. SUMOylation of the PR is hormone-dependent and has a suppressive effect on transcription of an exogenous promoter. Here we show that repression of PR activity by SUMOylation at Lys-388 is uncoupled from phosphorylation, involves synergy between tandem progesterone response elements, and is associated with lowered ligand sensitivity and slowed ligand-dependent down-regulation. However, paradoxically, cellular overexpression of SUMO-1 increases PR transcriptional activity even if Lys-388 is mutated, suggesting that the receptors are activated indirectly by other SUMOylated proteins. One of these is the coactivator SRC-1, whose binding to PR and enhancement of agonist-dependent N-/C-terminal interactions is augmented by the presence of SUMO-1. Increased transcription due to SRC-1 is independent of PR SUMOylation based on assays with the Lys-388 mutants and the pure antiprogestin ZK98299, which blocks N-/C-terminal interactions. In summary, SUMOylation tightly regulates the transcriptional activity of PR by repressing the receptors directly while activating them indirectly through augmented SRC-1 coactivation.
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Affiliation(s)
- Hany Abdel-Hafiz
- Department of Medicine, Division of Endocrinology, University of Colorado Denver, Anschutz Medical Campus, Aurora, Colorado 80045, USA.
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Genomics of signaling crosstalk of estrogen receptor alpha in breast cancer cells. PLoS One 2008; 3:e1859. [PMID: 18365014 PMCID: PMC2268000 DOI: 10.1371/journal.pone.0001859] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2007] [Accepted: 02/22/2008] [Indexed: 12/13/2022] Open
Abstract
Background The estrogen receptor α (ERα) is a ligand-regulated transcription factor. However, a wide variety of other extracellular signals can activate ERα in the absence of estrogen. The impact of these alternate modes of activation on gene expression profiles has not been characterized. Methodology/Principal Findings We show that estrogen, growth factors and cAMP elicit surprisingly distinct ERα-dependent transcriptional responses in human MCF7 breast cancer cells. In response to growth factors and cAMP, ERα primarily activates and represses genes, respectively. The combined treatments with the anti-estrogen tamoxifen and cAMP or growth factors regulate yet other sets of genes. In many cases, tamoxifen is perverted to an agonist, potentially mimicking what is happening in certain tamoxifen-resistant breast tumors and emphasizing the importance of the cellular signaling environment. Using a computational analysis, we predicted that a Hox protein might be involved in mediating such combinatorial effects, and then confirmed it experimentally. Although both tamoxifen and cAMP block the proliferation of MCF7 cells, their combined application stimulates it, and this can be blocked with a dominant-negative Hox mutant. Conclusions/Significance The activating signal dictates both target gene selection and regulation by ERα, and this has consequences on global gene expression patterns that may be relevant to understanding the progression of ERα-dependent carcinomas.
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Malek D, Gust R, Kleuser B. 17-Beta-estradiol inhibits transforming-growth-factor-beta-induced MCF-7 cell migration by Smad3-repression. Eur J Pharmacol 2006; 534:39-47. [PMID: 16497293 DOI: 10.1016/j.ejphar.2006.01.025] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2005] [Revised: 01/10/2006] [Accepted: 01/11/2006] [Indexed: 11/18/2022]
Abstract
Motility of malignant cells plays a crucial role for the metastasis of tumours. Both, 17-beta-estradiol and transforming growth factor-beta (TGF-beta), induce migration of MCF-7 breast cancer cells and simultaneous treatment resulted in an additive effect of the migratory response. But most interestingly, when cells were preincubated with 17-beta-estradiol, the ability of TGF-beta to evoke chemotaxis was drastically diminished. Abrogation of Smad signalling indicated that this pathway is essential for TGF-beta-mediated MCF-7 cell migration. In agreement, pretreatment of MCF-7 cells with 17-beta-estradiol resulted in a reduced phosphorylation of Smad2 and Smad3 as well as a diminished Smad2 and Smad3 gene reporter activity in response to TGF-beta. Thus, these results indicate a controversial role of 17-beta-estradiol on MCF-7 cell migration. 17-Beta-estradiol potently increases the migratory potency of MCF-7 cells, but inhibits TGF-beta-induced migration by an interaction between estrogen receptors and Smad proteins.
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Affiliation(s)
- Daniela Malek
- Institute of Pharmacy, Freie Universität Berlin, Königin-Luise-Str. 2+4, D-14195 Berlin, Germany
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Vivacqua A, Recchia AG, Fasanella G, Gabriele S, Carpino A, Rago V, Di Gioia ML, Leggio A, Bonofiglio D, Liguori A, Maggiolini M. The food contaminants bisphenol A and 4-nonylphenol act as agonists for estrogen receptor alpha in MCF7 breast cancer cells. Endocrine 2003; 22:275-84. [PMID: 14709801 DOI: 10.1385/endo:22:3:275] [Citation(s) in RCA: 78] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/18/2003] [Revised: 09/23/2003] [Accepted: 10/06/2003] [Indexed: 11/11/2022]
Abstract
Xenoestrogens are chemically distinct industrial products potentially able to disrupt the endocrine system by mimicking the action of endogenous steroid hormones. Among such compounds, the ubiquitous environmental contaminants bisphenol A (BPA) and 4-nonylphenol (NPH) may promote adverse effects in humans triggering estrogenic signals in target tissues. Following a research program on human exposure to endocrine disruptors, we found contamination of fresh food by BPA and NPH. More important, these contaminants were found to display estrogen-like activity using as a model system the estrogen-dependent MCF7 breast cancer cells (MCF7wt); its variant named MCF7SH, which is hormone-independent but still ERalpha-positive, and the steroid receptor-negative human cervical carcinoma HeLa cells. In transfection experiments BPA and NPH activated in a direct manner the endogenous ERalpha in MCF7wt and MCF7SH cells, as the antiestrogen hydroxytamoxifen was able to reverse both responses. Moreover, only the hormone-binding domains of ERalpha and ERbeta expressed by chimeric proteins in HeLa cells were sufficient to elicit the transcriptional activity upon BPA and NPH treatments. Transfecting the same cell line with ERalpha mutants, both contaminants triggered an estrogen-like response. These transactivation properties were interestingly supported in MCF7wt cells by the autoregulation of ERalpha which was assessed by RT-PCR for the mRNA evaluation and by immunoblotting and immunocytochemistry for the determination of protein levels. The ability of BPA and NPH to modulate gene expression was further confirmed by the upregulation of an estrogen target gene like pS2. As a biological counterpart, concentrations of xenoestrogens eliciting transcriptional activity were able to stimulate the proliferation of MCF7wt and MCFSH cells. Only NPH at a dose likely too high to be of any physiological relevance induced a severe cytotoxicity in an ERalpha-independent manner as ascertained in HeLa cells. The estrogenic effects of such industrial agents together with an increasing widespread human exposure should be taken into account for the potential influence also on hormone-dependent breast cancer disease.
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MESH Headings
- Benzhydryl Compounds
- Blotting, Western
- Breast Neoplasms/genetics
- Breast Neoplasms/metabolism
- Cell Division/drug effects
- Cell Line, Tumor
- Environmental Pollutants/pharmacology
- Estrogen Receptor alpha
- Estrogens, Non-Steroidal/pharmacology
- Female
- Food Contamination
- Gene Expression Regulation, Neoplastic/drug effects
- Humans
- Immunohistochemistry
- Neoplasms, Hormone-Dependent/genetics
- Neoplasms, Hormone-Dependent/metabolism
- Phenols/pharmacology
- RNA, Messenger/biosynthesis
- RNA, Messenger/genetics
- Receptors, Estrogen/agonists
- Receptors, Estrogen/biosynthesis
- Receptors, Estrogen/genetics
- Reverse Transcriptase Polymerase Chain Reaction
- Transcriptional Activation/drug effects
- Transfection
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Affiliation(s)
- Adele Vivacqua
- Department of Pharmaco-Biology, University of Calabria, 87036 Rende (CS), Italy
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Maggiolini M, Vivacqua A, Carpino A, Bonofiglio D, Fasanella G, Salerno M, Picard D, Andó S. The mutant androgen receptor T877A mediates the proliferative but not the cytotoxic dose-dependent effects of genistein and quercetin on human LNCaP prostate cancer cells. Mol Pharmacol 2002; 62:1027-35. [PMID: 12391264 DOI: 10.1124/mol.62.5.1027] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
High consumption of soybean products, such as phytoestrogens, has been hypothesized to contribute to a reduced incidence of prostate cancer in Southeast Asian people, although there have been inconsistent results among studies. Human LNCaP cells, extensively used as a model for androgen-dependent prostate tumor, express the androgen receptor (AR) mutant T877A promiscuously transactivated by estrogens and other ligands, which may further facilitate cancer progression. Here, for the first time to our knowledge, we demonstrate that genistein and quercetin, two phytoestrogens abundantly present in soybeans, activate either the AR mutant T877A in LNCaP or in transfected Chinese hamster ovary cells. This observation is supported by their capability to induce AR accumulation in the nuclear compartment of LNCaP together with mRNA down-regulation of the androgen target genes AR and PAP, and PSA up-regulation. Of interest, at concentrations eliciting transcriptional activity, both genistein and quercetin stimulate LNCaP cell growth, whereas at high levels, they become cytotoxic independently of AR expression, as ascertained in steroid receptor-negative Hela cells. The results of our study provide evidence that phytoestrogens may regulate several signaling processes in LNCaP cells; however, further studies are needed to assess their potential capability to restrain prostate tumor progression.
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Brandt R, Ebert AD. Growth inhibitors for mammary epithelial cells. PROGRESS IN MOLECULAR AND SUBCELLULAR BIOLOGY 1999; 20:197-248. [PMID: 9928532 DOI: 10.1007/978-3-642-72149-6_10] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- R Brandt
- Novartis Pharma Inc., Basel, Switzerland
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Tomita S, Deguchi S, Miyaguni T, Muto Y, Tamamoto T, Toda T. Analyses of microsatellite instability and the transforming growth factor-beta receptor type II gene mutation in sporadic breast cancer and their correlation with clinicopathological features. Breast Cancer Res Treat 1999; 53:33-9. [PMID: 10206070 DOI: 10.1023/a:1006167210269] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
To determine the incidence of microsatellite instability (MSI) and its relationship with both clinicopathologic parameters and patient survival, 101 cases of breast cancer were investigated. In addition, transforming growth factor-beta (TGF-beta) receptor type II (RII) gene mutation was also examined to clarify the relation to MSI in breast cancer development. MSI and RII gene mutation were screened by single strand conformation polymorphism (SSCP). The mutations of the RII gene were confirmed by a direct sequence. An association between the MSI status and the clinicopathological features was examined to assess the potential of the MSI status as a prognostic indicator in sporadic breast cancer cases. MSI was detected in 12 of 101 (11.9%) breast cancer cases. The positive MSI breast cancer cases showed relatively more advanced disease than negative MSI cases, and also exhibited relatively poorer prognoses. No RII gene mutations were observed in any of the breast cancer cases. Our data suggest that the MSI status may thus be a useful indicator for the prognosis of sporadic breast cancer cases. However, the breast seems to be an infrequent target organ for cancer development through RII gene mutations. As a result, tumor progression through this pathway appears to be related to organ specificity. For positive MSI breast cancers, other target genes therefore still need to be identified.
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Affiliation(s)
- S Tomita
- First Department of Surgery, School of Medicine, University of the Ryukyus, Okinawa, Japan.
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Foidart JM, Colin C, Denoo X, Desreux J, Béliard A, Fournier S, de Lignières B. Estradiol and progesterone regulate the proliferation of human breast epithelial cells. Fertil Steril 1998; 69:963-9. [PMID: 9591509 DOI: 10.1016/s0015-0282(98)00042-9] [Citation(s) in RCA: 103] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
OBJECTIVE To study the effects of estradiol and progesterone on the proliferation of normal human breast epithelial cells in vivo. DESIGN Double-blind randomized study. SETTING Departments of gynecology and of cell biology at a university hospital. PATIENT(S) Forty postmenopausal women with untreated menopause and documented plasma FSH levels of >30 mIU/mL and estradiol levels of <20 pg/mL. INTERVENTION(S) Daily topical application to both breasts of a gel containing a placebo, estradiol, progesterone, or a combination of estradiol and progesterone during the 14 days preceding esthetic breast surgery or excision of a benign lesion. MAIN OUTCOME MEASURE(S) Plasma and breast tissue concentrations of estradiol and progesterone. Epithelial cell cycles were evaluated in normal breast tissue by counting mitoses and performing quantitative proliferating cell nuclear antigen immunolabeling analyses. RESULT(S) Increasing the estradiol concentration enhanced the number of cycling epithelial cells, whereas increasing the progesterone concentration significantly limited the number of cycling epithelial cells. CONCLUSION(S) Exposure to progesterone for 14 days reduced the estradiol-induced proliferation of normal breast epithelial cells in vivo.
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Castaño E, Chen CW, Vorojeikina DP, Notides AC. The role of phosphorylation in human estrogen receptor function. J Steroid Biochem Mol Biol 1998; 65:101-10. [PMID: 9699862 DOI: 10.1016/s0960-0760(97)00179-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
We have studied the role of phosphorylation of the human estrogen receptor (hER) at serine 118, which has been previously identified as a site important for transactivation. We have tested this transactivation in yeast and cell-free transcription assays, and have shown that mutation of serine 118 to alanine results in a 30-40% decrease in hER-dependent transcription. Furthermore, we investigated the functional significance of phosphorylation at this site by hormone binding and DNA binding. The mutation of serine 118 to alanine in the hER caused no decrease in its affinity for either estradiol or an ERE. The mutant receptor had an altered phosphorylation pattern when expressed in COS-1 and Sf9 cells, but not in HeLa cells. Our findings indicate that phosphorylation of serine 118 of the hER plays a role in regulating its transcriptional activity.
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Affiliation(s)
- E Castaño
- Department MCB, Harvard University, Cambridge, MA 02138, USA.
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