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Gompel A, Seifert-Klauss V, Simon JA, Prior JC. Lack of evidence that progesterone in ovulatory cycles causes breast cancer. Climacteric 2023; 26:634-637. [PMID: 37671636 DOI: 10.1080/13697137.2023.2249813] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2023] [Accepted: 08/12/2023] [Indexed: 09/07/2023]
Abstract
A recent Perspective article asserted that progesterone secretion during ovulatory cycles is the cause of breast cancer. However, we challenge most of the evidence developed in this publication. First, there is a lack of evidence that progesterone is mutagenic for breast cells. Cause of a cancer should mean initiation by mutation, as opposed to promotion. Second, subclinical ovulatory disturbances occur rather frequently in normal-length menstrual cycles. Third, the authors attribute a potential carcinogenic effect to progesterone secreted during menstrual cycles but not to progesterone during pregnancy. They did not discuss breast cancer evidence from progesterone/progestin therapeutics. They argue that in genetic primary amenorrhea, a hypothetic lower risk of breast cancer could be due to the lack of progesterone, despite the progesterone/progestin in hormone replacements these women receive. Fourth, they advocate a regulatory effect of progesterone on several genes potentially involved in cancer genesis. In particular, they attribute a lower risk of breast cancer in women with Mayer-Rokitansky-Küster-Hauser syndrome to a defect in the progesterone-stimulated Wnt4 gene. However, this defect is only present in a small subset. Thus, the postulated progesterone breast cancer risk is unconvincing, which we discuss point by point in this commentary.
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Affiliation(s)
- A Gompel
- Gynecology-Endocrinology, Paris-Cité University, Paris, France
| | | | - J A Simon
- IntimMedicine Specialists, George Washington University, Washington, DC, USA
| | - J C Prior
- Endocrinology & Medicine, University of British Columbia, Vancouver, BC, Canada
- Centre for Menstrual Cycle and Ovulation Research, University of British Columbia, Vancouver, BC, Canada
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2
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Geerts D, Chopra C, Connelly L. Osteoprotegerin: Relationship to Breast Cancer Risk and Prognosis. Front Oncol 2020; 10:462. [PMID: 32318347 PMCID: PMC7154067 DOI: 10.3389/fonc.2020.00462] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2020] [Accepted: 03/16/2020] [Indexed: 01/14/2023] Open
Abstract
Osteoprotegerin (OPG) is a secreted member of the Tumor Necrosis Factor (TNF) receptor superfamily (TNFRSF11B), that was first characterized and named for its protective role in bone remodeling. In this context, OPG binds to another TNF superfamily member Receptor Activator of NF-kappaB Ligand (RANKL; TNFSF11) and blocks interaction with RANK (TNFRSF11A), preventing RANKL/RANK stimulation of osteoclast maturation, and bone breakdown. Further studies revealed that OPG protein is also expressed by tumor cells and led to investigation of the role of OPG in tumor biology. An increasing body of data has demonstrated that OPG modulates breast tumor behavior. Initially, research was focused on OPG in the bone microenvironment as a potential inhibitor of RANKL-driven osteolysis. More recently, attention has shifted to include OPG expression and interactions in the primary breast tumor independent of RANKL. In the primary tumor, OPG may interact with another TNF superfamily member, TNF-Related Apoptosis Inducing Ligand (TRAIL; TNFSF10) to prevent apoptosis induction. Additional interest in OPG in breast cancer has been stimulated by the tumor-promoting role of its binding partner RANKL in association with BRCA1 gene mutations. We and others have previously summarized the functional studies on OPG and breast cancer (1, 2). After basic research studies on the in vitro role for OPG (and RANKL) in breast cancer, the field now expands to assess the in vivo role for OPG by examining the correlation between OPG expression and breast cancer risk or patient prognosis. However, the data reported so far is conflicting, since OPG expression appears linked to both good and poor patient survival. In the current review we will summarize these studies. Our goal is to provide stimulus for further research to bridge the basic research findings and clinical data regarding OPG in breast cancer.
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Affiliation(s)
- Dirk Geerts
- Department of Medical Biology, Academic Medical Center Amsterdam, Amsterdam, Netherlands
| | - Christina Chopra
- School of Medicine, California University of Science and Medicine, San Bernardino, CA, United States
| | - Linda Connelly
- School of Medicine, California University of Science and Medicine, San Bernardino, CA, United States
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3
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Zhao H, Sun Z, Ma Y, Song R, Yuan Y, Bian J, Gu J, Liu Z. Antiosteoclastic bone resorption activity of osteoprotegerin via enhanced AKT/mTOR/ULK1-mediated autophagic pathway. J Cell Physiol 2019; 235:3002-3012. [PMID: 31535378 DOI: 10.1002/jcp.29205] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Accepted: 09/03/2019] [Indexed: 12/20/2022]
Abstract
Autophagy plays a critical role in the maintenance of bone homeostasis. Osteoprotegerin (OPG) is an inhibitor of osteoclast-mediated bone resorption. However, whether autophagy is involved in the antiosteoclastogenic effects of OPG remains unclear. The present study aimed to investigate the potential mechanism of autophagy during OPG-induced bone resorption via inhibition of osteoclasts differentiated from bone marrow-derived macrophages in BALB/c mice. The results showed that after treatment with receptor activator of nuclear factor-κΒ ligand and macrophage colony-stimulating factor for 3 days, TRAP+ osteoclasts formed, representing the resting state of autophagy. These osteoclasts were treated with OPG and underwent autophagy, as demonstrated by LC3-II accumulation, acidic vesicular organelle formation, and the presence of autophagosomes. The levels of autophagy-related proteins, LC3-II increased and P62 decreased at 3 hr in OPG-treated osteoclasts. The viability, differentiation, and bone resorption activity of osteoclasts declined after OPG treatment. Treatment with OPG and chloroquine, an autophagy inhibitor, attenuated OPG-induced inhibition of osteoclastic bone resorption, whereas rapamycin (RAP), an autophagy inducer, enhanced OPG-induced inhibition of differentiation, survival, and bone resorption activity of osteoclasts. Furthermore, OPG reduced the amount of phosphorylated(p) protein kinase B (AKT) and pmTOR and increased the level of pULK, in a dose-dependant manner. LY294002, a phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K)/AKT pathway inhibitor, attenuated the decline in pAKT, but enhanced the decline in pmTOR and the increase in pULK1 following OPG treatment. RAP enhanced the OPG-induced increase in pULK1. The PI3K inhibitor 3-methyladenine partly blocked OPG-induced autophagy. Thus, the results revealed that OPG inhibits osteoclast bone resorption by inducing autophagy via the AKT/mTOR/ULK1 signaling pathway.
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Affiliation(s)
- Hongyan Zhao
- College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, China.,Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou University, Yangzhou, Jiangsu, China.,Joint International Research Laboratory of Agriculture and Agri-Product Safety, The Ministry of Education of China, Yangzhou University, Yangzhou, Jiangsu, China
| | - Ziqiang Sun
- College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, China.,Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou University, Yangzhou, Jiangsu, China.,Joint International Research Laboratory of Agriculture and Agri-Product Safety, The Ministry of Education of China, Yangzhou University, Yangzhou, Jiangsu, China
| | - Yonggang Ma
- College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, China.,Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou University, Yangzhou, Jiangsu, China.,Joint International Research Laboratory of Agriculture and Agri-Product Safety, The Ministry of Education of China, Yangzhou University, Yangzhou, Jiangsu, China
| | - Ruilong Song
- College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, China.,Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou University, Yangzhou, Jiangsu, China.,Joint International Research Laboratory of Agriculture and Agri-Product Safety, The Ministry of Education of China, Yangzhou University, Yangzhou, Jiangsu, China
| | - Yan Yuan
- College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, China.,Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou University, Yangzhou, Jiangsu, China.,Joint International Research Laboratory of Agriculture and Agri-Product Safety, The Ministry of Education of China, Yangzhou University, Yangzhou, Jiangsu, China
| | - Jianchun Bian
- College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, China.,Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou University, Yangzhou, Jiangsu, China.,Joint International Research Laboratory of Agriculture and Agri-Product Safety, The Ministry of Education of China, Yangzhou University, Yangzhou, Jiangsu, China
| | - Jianhong Gu
- College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, China.,Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou University, Yangzhou, Jiangsu, China.,Joint International Research Laboratory of Agriculture and Agri-Product Safety, The Ministry of Education of China, Yangzhou University, Yangzhou, Jiangsu, China
| | - Zongping Liu
- College of Veterinary Medicine, Yangzhou University, Yangzhou, Jiangsu, China.,Jiangsu Co-Innovation Center for Prevention and Control of Important Animal Infectious Diseases and Zoonoses, Yangzhou University, Yangzhou, Jiangsu, China.,Joint International Research Laboratory of Agriculture and Agri-Product Safety, The Ministry of Education of China, Yangzhou University, Yangzhou, Jiangsu, China
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4
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Infante M, Fabi A, Cognetti F, Gorini S, Caprio M, Fabbri A. RANKL/RANK/OPG system beyond bone remodeling: involvement in breast cancer and clinical perspectives. JOURNAL OF EXPERIMENTAL & CLINICAL CANCER RESEARCH : CR 2019; 38:12. [PMID: 30621730 PMCID: PMC6325760 DOI: 10.1186/s13046-018-1001-2] [Citation(s) in RCA: 102] [Impact Index Per Article: 20.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/08/2018] [Accepted: 12/11/2018] [Indexed: 12/21/2022]
Abstract
RANKL/RANK/OPG system consists of three essential signaling molecules: i) the receptor activator of nuclear factor (NF)-kB-ligand (RANKL), ii) the receptor activator of NF-kB (RANK), and iii) the soluble decoy receptor osteoprotegerin (OPG). Although this system is critical for the regulation of osteoclast differentiation/activation and calcium release from the skeleton, different studies have elucidated its specific role in mammary gland physiology and hormone-driven epithelial proliferation during pregnancy. Of note, several data suggest that progesterone induces mammary RANKL expression in mice and humans. In turn, RANKL controls cell proliferation in breast epithelium under physiological conditions typically associated with higher serum progesterone levels, such as luteal phase of the menstrual cycle and pregnancy. Hence, RANKL/RANK system can be regarded as a major downstream mediator of progesterone-driven mammary epithelial cells proliferation, potentially contributing to breast cancer initiation and progression. Expression of RANKL, RANK, and OPG has been detected in breast cancer cell lines and in human primary breast cancers. To date, dysregulation of RANKL/RANK/OPG system at the skeletal level has been widely documented in the context of metastatic bone disease. In fact, RANKL inhibition through the RANKL-blocking human monoclonal antibody denosumab represents a well-established therapeutic option to prevent skeletal-related events in metastatic bone disease and adjuvant therapy-induced bone loss in breast cancer. On the other hand, the exact role of OPG in breast tumorigenesis is still unclear. This review focuses on molecular mechanisms linking RANKL/RANK/OPG system to mammary tumorigenesis, highlighting pre-clinical and clinical evidence for the potential efficacy of RANKL inhibition as a prevention strategy and adjuvant therapy in breast cancer settings.
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Affiliation(s)
- Marco Infante
- Unit of Endocrinology and Metabolic Diseases, Department of Systems Medicine, CTO A. Alesini Hospital, ASL Roma 2, University Tor Vergata, Via San Nemesio, 21, 00145, Rome, Italy
| | - Alessandra Fabi
- Division of Medical Oncology 1, Regina Elena National Cancer Institute, Via Elio Chianesi, 53, 00144, Rome, Italy
| | - Francesco Cognetti
- Division of Medical Oncology 1, Regina Elena National Cancer Institute, Via Elio Chianesi, 53, 00144, Rome, Italy
| | - Stefania Gorini
- Laboratory of Cardiovascular Endocrinology, IRCCS San Raffaele Pisana, Via di Val Cannuta, 247, 00166, Rome, Italy
| | - Massimiliano Caprio
- Laboratory of Cardiovascular Endocrinology, IRCCS San Raffaele Pisana, Via di Val Cannuta, 247, 00166, Rome, Italy.,Department of Human Sciences and Promotion of the Quality of Life, San Raffaele Roma Open University, Via di Val Cannuta, 247, 00166, Rome, Italy
| | - Andrea Fabbri
- Unit of Endocrinology and Metabolic Diseases, Department of Systems Medicine, CTO A. Alesini Hospital, ASL Roma 2, University Tor Vergata, Via San Nemesio, 21, 00145, Rome, Italy.
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5
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Design, synthesis and biological evaluation of novel indole-xanthendione hybrids as selective estrogen receptor modulators. Bioorg Med Chem 2017; 26:266-277. [PMID: 29198894 DOI: 10.1016/j.bmc.2017.11.040] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2017] [Revised: 10/27/2017] [Accepted: 11/25/2017] [Indexed: 01/21/2023]
Abstract
Ground breaking clinical therapeutic advances in the treatment of breast cancer (BC) is the introduction of selective estrogen receptor modulators (SERMs). We have expeditiously designed and synthesized indole-xanthendione hybrids by coalescing the indole nucleus with xanthendione. All the compounds were first screened for anti-proliferative activity, cytotoxicity and ER-α binding affinity by utilizing ER-α dominant T47D BC cell lines, PBMCs and ER-α competitor assay kit. From this study, two representative compounds 6e and 6f showing most promising activity were advanced for gene expression studies for targeting ER-α. Cell imaging experiment undoubtedly indicate that both the compounds were able to cross cellular bio membrane and accumulate thus instigating cytotoxicity. RT-PCR and Western blotting experiments further strengthened that both compounds altered the expression of mRNA and receptor protein of ER-α, thereby forestalling downstream transactivation and signalling pathway in T47D cells line. Structural investigation from induced fit simulation study suggest that indole moiety of the compounds 6e and 6f helps in the anchoring of the xanthendione moiety in the hydrophobic region of the cavity thus enabling the compound to bind in antagonistic conformation similar to bazedoxifene by extensive hydrogen bonding and Van der Waals forces. All these finding collectively imply that compound 6e and 6f represents a novel potent ER-α antagonist and in the development of SERMs for the management of BC.
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6
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Jia J, Zhou H, Zeng X, Feng S. Estrogen stimulates osteoprotegerin expression via the suppression of miR-145 expression in MG-63 cells. Mol Med Rep 2017; 15:1539-1546. [PMID: 28260003 PMCID: PMC5364970 DOI: 10.3892/mmr.2017.6168] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Accepted: 12/12/2016] [Indexed: 12/24/2022] Open
Abstract
Osteoprotegerin (OPG) is implicated in the pathogenesis of postmenopausal osteoporosis, and other metabolic bone diseases caused by estrogen deficiency. Previous studies have demonstrated that estrogen may stimulate OPG expression in osteoblast cells at the transcriptional level; however, whether estrogen can regulate OPG expression at a post-transcriptional level remains elusive. The present study aimed to investigate the role of microRNA (miRNA) in estrogen-mediated OPG production in human osteoblast-like MG-63 cells. The results from ELISA, western blotting and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) confirmed that estrogen may upregulate OPG expression. Mechanistic studies indicated that estrogen increased the activity of a luciferase reporter harboring the OPG 3′-untranslated region (3′-UTR). Bioinformatics analysis demonstrated that there is a potential targeting site in the OPG 3′-UTR for miRNA (miR)-145, which is associated with osteoblast differentiation. The results of an RT-qPCR suggested that estrogen suppressed miR-145 expression. In addition, dual-luciferase assay, RT-qPCR and western blot analysis indicated that miR-145 directly targets and negatively regulates OPG expression. Furthermore, transfection of cells with miR-145 mimics was able to partially inhibit the induction of OPG expression by estrogen, thus confirming the role of miR-145 in estrogen-mediated OPG induction. Taken together, the results of the present study demonstrated that estrogen may post-transcriptionally regulate OPG expression through suppression of miR-145 expression.
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Affiliation(s)
- Jun Jia
- Department of Orthopaedics, Tianjin Medical University General Hospital, Tianjin 300052, P.R. China
| | - Hengxing Zhou
- Department of Orthopaedics, Tianjin Medical University General Hospital, Tianjin 300052, P.R. China
| | - Xiantie Zeng
- Department of Surgery of Foot and Ankle, Tianjin Hospital, Tianjin 300211, P.R. China
| | - Shiqing Feng
- Department of Orthopaedics, Tianjin Medical University General Hospital, Tianjin 300052, P.R. China
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7
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Owen S, Zabkiewicz C, Ye L, Sanders AJ, Gong C, Jiang WG. Key Factors in Breast Cancer Dissemination and Establishment at the Bone: Past, Present and Future Perspectives. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2017; 1026:197-216. [PMID: 29282685 DOI: 10.1007/978-981-10-6020-5_9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
Bone metastases associated with breast cancer remain a clinical challenge due to their associated morbidity, limited therapeutic intervention and lack of prognostic markers. With a continually evolving understanding of bone biology and its dynamic microenvironment, many potential new targets have been proposed. In this chapter, we discuss the roles of well-established bone markers and how their targeting, in addition to tumour-targeted therapies, might help in the prevention and treatment of bone metastases. There are a vast number of bone markers, of which one of the best-known families is the bone morphogenetic proteins (BMPs). This chapter focuses on their role in breast cancer-associated bone metastases, associated signalling pathways and the possibilities for potential therapeutic intervention. In addition, this chapter provides an update on the role receptor activator of nuclear factor-κB (RANK), RANK ligand (RANKL) and osteoprotegerin (OPG) play on breast cancer development and their subsequent influence during the homing and establishment of breast cancer-associated bone metastases. Beyond the well-established bone molecules, this chapter also explores the role of other potential factors such as activated leukocyte cell adhesion molecule (ALCAM) and its potential impact on breast cancer cells' affinity for the bone environment, which implies that ALCAM could be a promising therapeutic target.
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Affiliation(s)
- Sioned Owen
- Cardiff University School of Medicine, CCMRC, Cardiff University, Henry Wellcome Building, Heath Park, Cardiff, CF14 4XN, UK
| | - Catherine Zabkiewicz
- Cardiff University School of Medicine, CCMRC, Cardiff University, Henry Wellcome Building, Heath Park, Cardiff, CF14 4XN, UK
| | - Lin Ye
- Cardiff University School of Medicine, CCMRC, Cardiff University, Henry Wellcome Building, Heath Park, Cardiff, CF14 4XN, UK
| | - Andrew J Sanders
- Cardiff University School of Medicine, CCMRC, Cardiff University, Henry Wellcome Building, Heath Park, Cardiff, CF14 4XN, UK
| | - Chang Gong
- Cardiff University School of Medicine, CCMRC, Cardiff University, Henry Wellcome Building, Heath Park, Cardiff, CF14 4XN, UK.,Sun Yat-sen Memorial Hospital, Sun Yat-sen University, Guangzhou, 510120, China
| | - Wen G Jiang
- Cardiff University School of Medicine, CCMRC, Cardiff University, Henry Wellcome Building, Heath Park, Cardiff, CF14 4XN, UK.
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Vriend J, Reiter RJ. Breast cancer cells: Modulation by melatonin and the ubiquitin-proteasome system--a review. Mol Cell Endocrinol 2015; 417:1-9. [PMID: 26363225 DOI: 10.1016/j.mce.2015.09.001] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Accepted: 09/01/2015] [Indexed: 02/07/2023]
Abstract
Melatonin inhibits human breast cancer cells stimulated with estrogen. This antiproliferative action depends on the presence of the estrogen receptor alpha (ERα) in the human MCF-7 cell line and is strictly dose-dependent. Since researchers concerned with melatonin and breast cancer have not considered the relevance of the ubiquitin-proteasome system to this research in this review we do so. The fact that the first breast cancer susceptibility gene to be identified, Brca1, functions as a ubiquitin ligase indicates that the ubiquitin-proteasome system has a role in regulating susceptibility to breast cancer. While mutations of this gene increase the incidence of breast cancer, the wild type gene suppresses estrogen-dependent transcriptional events relying on the estrogen receptor ERα. Three other ubiquitin ligases, SCF(Skp2), E6AP and APC, interact directly with ERα at the ERE and AP-1 promoters of ERα target genes. Melatonin, like proteasome inhibitors, decreases estrogen-induced gene transcription. Indeed, it has been reported that melatonin specifically inhibits estrogen-induced transcription mediated by ERα at the ERE and AP1 gene promoters. Herein, we present a model in which the inhibitory action of melatonin on MCF-7 cells is mediated, directly or indirectly, by the ubiquitin-proteasome system. In this model ERα, apoptotic proteins, and cell cycle proteins, all influenced by melatonin, are substrates of key ubiquitin ligases including SCF(Skp2), E6AP, and SCF(B-TrCP). Since dysfunction of the ubiquitin-proteasome system is a risk factor for breast cancer, this model provides a context in which to test the clinical potential, and limitations, of melatonin and proteasome inhibitors.
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Affiliation(s)
- Jerry Vriend
- Department of Human Anatomy and Cell Science, University of Manitoba, Winnipeg, MB, Canada.
| | - Russel J Reiter
- Department of Cellular and Structural Biology, UT Health Science Center San Antonio, TX, USA
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9
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Weichhaus M, Chung STM, Connelly L. Osteoprotegerin in breast cancer: beyond bone remodeling. Mol Cancer 2015; 14:117. [PMID: 26054853 PMCID: PMC4460694 DOI: 10.1186/s12943-015-0390-5] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Accepted: 05/20/2015] [Indexed: 11/28/2022] Open
Abstract
Osteoprotegerin (OPG) is a secreted protein and member of the Tumor Necrosis Factor (TNF) Receptor superfamily. OPG has been well characterized as a regulator of bone metabolism which acts by blocking osteoclast maturation and preventing bone breakdown. Given this role, early studies on OPG in breast cancer focused on the administration of OPG in order to prevent the osteolysis observed with bone metastases. However OPG is also produced by the breast tumor cells themselves. Research focusing on OPG produced by breast tumor cells has revealed actions of OPG which promote tumor progression. In vitro studies into the role of OPG produced by breast tumor cells have demonstrated that OPG can block TNF-related apoptosis inducing ligand (TRAIL)-mediated apoptosis. Furthermore, in vivo studies show that OPG expression by breast tumors can promote tumor growth and metastasis. In addition it has been shown that OPG stimulates endothelial cell survival and tube formation thus it may indirectly promote breast tumor progression through impacting angiogenesis. This article will present a summary of the data concerning the tumor-promoting effects of OPG in breast cancer.
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Affiliation(s)
- Michael Weichhaus
- Division of Natural Science and Mathematics, Chaminade University of Honolulu, 3140 Waialae Avenue, Honolulu, HI, 96816, USA.
| | - Stephanie Tsang Mui Chung
- Department of Pharmaceutical Sciences, Daniel K. Inouye College of Pharmacy, University of Hawaii at Hilo, Hilo, HI, 96720, USA.
| | - Linda Connelly
- Department of Pharmaceutical Sciences, Daniel K. Inouye College of Pharmacy, University of Hawaii at Hilo, Hilo, HI, 96720, USA.
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10
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Weichhaus M, Segaran P, Renaud A, Geerts D, Connelly L. Osteoprotegerin expression in triple-negative breast cancer cells promotes metastasis. Cancer Med 2014; 3:1112-25. [PMID: 24976340 PMCID: PMC4302663 DOI: 10.1002/cam4.277] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2013] [Revised: 04/29/2014] [Accepted: 05/01/2014] [Indexed: 01/12/2023] Open
Abstract
Osteoprotegerin (OPG) is a secreted member of the tumor necrosis factor (TNF) receptor superfamily that has been well characterized as a negative regulator of bone remodeling. OPG is also expressed in human breast cancer tissues and cell lines. In vitro studies suggest that OPG exerts tumor-promoting effects by binding to TNF-related apoptosis inducing ligand (TRAIL), thereby preventing induction of apoptosis. However, the in vivo effect of OPG expression by primary breast tumors has not been characterized. We knocked down OPG expression in MDA-MB-231 and MDA-MB-436 human breast cancer cells using shRNA and siRNA to investigate impact on metastasis in the chick embryo model. We observed a reduction in metastasis with OPG knockdown cells. We found that lowering OPG expression did not alter sensitivity to TRAIL-induced apoptosis; however, the OPG knockdown cells had a reduced level of invasion. In association with this we observed reduced expression of the proteases Cathepsin D and Matrix Metalloproteinase-2 upon OPG knockdown, indicating that OPG may promote metastasis via modulation of protease expression and invasion. We conclude that OPG has a metastasis-promoting effect in breast cancer cells.
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Affiliation(s)
- Michael Weichhaus
- Department of Pharmaceutical Sciences, College of Pharmacy, University of Hawaii at Hilo, Hilo, Hawaii
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Abstract
Acting through its cognate receptor, receptor activator of nuclear factor-κB (RANK), RANK ligand (RANKL) is an essential mediator of osteoclast function and survival. Preclinical data have now firmly established that blockade of tumor-induced osteoclastogenesis by RANKL inhibition will not only protect against bone destruction but will also inhibit the progression of established bone metastases and delay the formation of de novo bone metastases in cancer models. In patients with bone metastases, skeletal complications are driven by increased osteoclastic activity and may result in pathological fractures, spinal cord compression and the need for radiotherapy to the bone or orthopedic surgery (collectively known as skeletal-related events (SREs)). Denosumab, a fully human monoclonal antibody against RANKL, has been demonstrated to prevent or delay SREs in patients with solid tumors that have metastasized to bone. In addition to its central role in tumor-induced osteolysis, bone destruction and skeletal tumor progression, there is emerging evidence for direct pro-metastatic effects of RANKL, independent of osteoclasts. For example, RANKL also stimulates metastasis via activity on RANK-expressing cancer cells, resulting in increased invasion and migration. Pharmacological inhibition of RANKL may also reduce bone and lung metastasis through blockade of the direct action of RANKL on metastatic cells. This review describes these distinct but potentially overlapping mechanisms by which RANKL may promote metastases.
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12
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Bone effects of mammalian target of rapamycin (mTOR) inhibition with everolimus. Crit Rev Oncol Hematol 2013; 87:101-11. [DOI: 10.1016/j.critrevonc.2013.05.015] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2013] [Revised: 05/22/2013] [Accepted: 05/31/2013] [Indexed: 01/28/2023] Open
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13
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Mozzanega B, Gizzo S, Bernardi D, Salmaso L, Patrelli TS, Mioni R, Finos L, Nardelli GB. Cyclic variations of bone resorption mediators and markers in the different phases of the menstrual cycle. J Bone Miner Metab 2013; 31:461-7. [PMID: 23479185 DOI: 10.1007/s00774-013-0430-4] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/03/2012] [Accepted: 01/24/2013] [Indexed: 11/29/2022]
Abstract
Female hormones are very important in regulating bone homeostasis; the drop of estrogen levels occurring at menopause is linked to a dramatic prevalence of bone resorption on formation. Only a small number of studies investigated the relationship between changes in circulating female sex hormones and the markers and mediators of bone homeostasis and they showed conflicting results. To explore such relationships we studied 20 young fertile healthy women, aged between 19 and 32 years. None had received hormone treatment for at least 6 months. We assayed luteinizing hormone, follicle-stimulating hormone, progesterone and 17β-estradiol, as well as the levels of osteoprotegerin (OPG), C-terminal telopeptide of collagen type I (CTx) and RANKL (receptor activator of nuclear factor-B ligand) in samples drawn from every subject at four different times during the menstrual cycle when estrogens are lowest, at the start of the cycle: T 0 (2-4th day); when estrogens are highest, in the pre-ovulatory period: T 14 (12-14th day); when progesterone activity is highest, in the advanced luteal phase: T 26 (24-26th day); and again at the start of the next cycle: T 01 (2-4th day). We observed that CTx levels are highest at the start of the cycle, decreased significantly from T 0 to T 26 (pfwe = 0.0455) and then increased from T 26 to T 01 (pfwe = 0.0415); OPG, on the other hand, which was also highest at the start of the cycle, decreased significantly from T 0 to T 14 (pfwe = 0.02) and then increased, though not significantly, from T 14 to T 01; no variation was observed in RANKL values at any time. We observed inverse correlations between estradiol and OPG levels, which became highly significant at T 01 between estradiol nadir and OPG peak levels (pfw = 0.0095). Furthermore, the increase of estradiol from T 0 to T 14 was negatively correlated with the concomitant decrease of OPG (pfwe = 0.0277), as was the fall of estradiol from T 26 to T 01 with the OPG peak levels, both at T 01 (pfw = 0.0045) and at T 0 (pfwe = 0.0381). We also observed direct correlations between the OPG levels and the variations of progesterone in the preceding intervals, but they never attained statistical significance. We conclude that OPG and CTx fluctuation during the menstrual cycle are likely due to the physiological variations of sex steroids levels.
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Affiliation(s)
- Bruno Mozzanega
- Dipartimento della Salute della Donna del Bambino, U.O.C. di Clinica Ginecologica e Ostetrica, Via Giustiniani 3, 35128, Padua, Italy
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14
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Hadji P, Coleman R, Gnant M, Green J. The impact of menopause on bone, zoledronic acid, and implications for breast cancer growth and metastasis. Ann Oncol 2012; 23:2782-2790. [PMID: 22730099 PMCID: PMC3477882 DOI: 10.1093/annonc/mds169] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Revised: 04/02/2012] [Accepted: 04/17/2012] [Indexed: 12/22/2022] Open
Abstract
Recent data from the AZURE, ABCSG-12, and ZO-FAST clinical trials have challenged our understanding of the potential anticancer activity of zoledronic acid (ZOL). Although the results of these studies may appear to be conflicting on the surface, a deeper look into commonalities among the patient populations suggest that some host factors (i.e. patient age and endocrine status) may contribute to the anticancer activity of ZOL. Indeed, data from these large clinical trials suggest that the potential anticancer activity of ZOL may be most robust in a low-estrogen environment. However, this may be only part of the story and many questions remain to be answered to fully explain the phenomenon. Does estrogen override the anticancer activity of ZOL seen in postmenopausal women? Are hormones other than estrogen involved that contribute to this effect? Does the role of bone turnover in breast cancer (BC) growth and progression differ in the presence of various estrogen levels? Here, we present a review of the multitude of factors affected by different endocrine environments in women with BC that may influence the potential anticancer activity of ZOL.
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Affiliation(s)
- P Hadji
- Department of Gynecology, Endocrinology, and Oncology, Philipps-University of Marburg, Marburg, Germany
| | - R Coleman
- Academic Unit of Clinical Oncology, Weston Park Hospital, CR-UK/YCR Sheffield Cancer Research Centre, Sheffield, UK
| | - M Gnant
- Department of Surgery, Comprehensive Cancer Center, Medical University of Vienna, Vienna, Austria
| | - J Green
- Department of Oncology, Novartis Pharma AG, Basel, Switzerland.
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15
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Sharma B, Singh RK. Emerging candidates in breast cancer stem cell maintenance, therapy resistance and relapse. J Carcinog 2011; 10:36. [PMID: 22279421 PMCID: PMC3263158 DOI: 10.4103/1477-3163.91119] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2011] [Accepted: 10/07/2011] [Indexed: 12/27/2022] Open
Abstract
Therapy resistance is a major concern while treating breast cancer. Various mechanisms have been proposed, but so far nothing has been able to effectively address this problem. Accumulating evidences suggest that a subset of cancer cells provides survival benefits to the tumor and are responsible for therapy resistance and relapse of cancer. These so called the cancer stem cells, are known to be regulated by several pathways. Evidences shows that the tumor microenvironment plays a crucial role in maintaining the cancer stem cell pool. Signaling within the tumor is modulated by surrounding cells which secrete signals favoring tumor growth and metastasis. In breast cancer, the cancer stem cells have recently been reported to be influenced by tumor microenvironment via cytokines which act as chemoattractants for leukocytes. This review elucidates the emerging role of chemokine receptor and receptor activator of NFκB (RANK) ligand/RANK signaling pathways in mediating therapy resistance of breast cancer by maintaining the cancer stem cell pool.
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Affiliation(s)
- Bhawna Sharma
- Department of Pathology and Microbiology, The University of Nebraska Medical Center, 985900 Nebraska Medical Center, Omaha, NE, 68198-5900, USA
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16
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Du J, Wei YJ, Peng C, Ran X, Zhang H, Jiang YP, Rahman K, Qin LP. Establishment of a luciferase assay-based screening system for detecting estrogen receptor agonists in plant extracts. Bone 2011; 49:572-9. [PMID: 21664503 DOI: 10.1016/j.bone.2011.05.028] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/06/2010] [Revised: 04/07/2011] [Accepted: 05/26/2011] [Indexed: 11/30/2022]
Abstract
In order to effectively treat osteoporosis and other bone-loss disorders, small compounds that could induce bone formation are needed. The present study attempted to establish a screening system for detecting estrogenic activity of compounds, which probably have anti-osteoporosis effects. For this purpose, we established osteoblastic-like MG63 cells stably transfected with the PGL3 reporter gene driven by a promoter consisting of three estrogen response elements (EREs). Using this system, we screened numerous plant extracts, and found several which displayed bioactivity. We conclude that the MG63 cells with estrogen-specific reporter plasmids (MG63-pERE) are useful for high-throughput screening of estrogen receptor agonists from plants which may have favorable potency and could be developed into novel anti-osteoporosis drugs.
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Affiliation(s)
- Jian Du
- Department of Pharmacognosy, School of Pharmacy, Second Military Medical University, Shanghai 200433, PR China
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17
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Simons R, Vincken JP, Mol LAM, The SAM, Bovee TFH, Luijendijk TJC, Verbruggen MA, Gruppen H. Agonistic and antagonistic estrogens in licorice root (Glycyrrhiza glabra). Anal Bioanal Chem 2011; 401:305-13. [PMID: 21573846 PMCID: PMC3124641 DOI: 10.1007/s00216-011-5061-9] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2011] [Revised: 04/21/2011] [Accepted: 04/25/2011] [Indexed: 01/06/2023]
Abstract
The roots of licorice (Glycyrrhiza glabra) are a rich source of flavonoids, in particular, prenylated flavonoids, such as the isoflavan glabridin and the isoflavene glabrene. Fractionation of an ethyl acetate extract from licorice root by centrifugal partitioning chromatography yielded 51 fractions, which were characterized by liquid chromatography-mass spectrometry and screened for activity in yeast estrogen bioassays. One third of the fractions displayed estrogenic activity towards either one or both estrogen receptors (ERs; ERα and ERβ). Glabrene-rich fractions displayed an estrogenic response, predominantly to the ERα. Surprisingly, glabridin did not exert agonistic activity to both ER subtypes. Several fractions displayed higher responses than the maximum response obtained with the reference compound, the natural hormone 17β-estradiol (E(2)). The estrogenic activities of all fractions, including this so-called superinduction, were clearly ER-mediated, as the estrogenic response was inhibited by 20-60% by known ER antagonists, and no activity was found in yeast cells that did not express the ERα or ERβ subtype. Prolonged exposure of the yeast to the estrogenic fractions that showed superinduction did, contrary to E(2), not result in a decrease of the fluorescent response. Therefore, the superinduction was most likely the result of stabilization of the ER, yeast-enhanced green fluorescent protein, or a combination of both. Most fractions displaying superinduction were rich in flavonoids with single prenylation. Glabridin displayed ERα-selective antagonism, similar to the ERα-selective antagonist RU 58668. Whereas glabridin was able to reduce the estrogenic response of E(2) by approximately 80% at 6 × 10(-6) M, glabrene-rich fractions only exhibited agonistic responses, preferentially on ERα.
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Affiliation(s)
- Rudy Simons
- Laboratory of Food Chemistry, Wageningen University, P.O. Box 8129, 6700 EV Wageningen, The Netherlands
- Frutarom Netherlands BV, Landjuweel 5, 3905 PE Veenendaal, The Netherlands
| | - Jean-Paul Vincken
- Laboratory of Food Chemistry, Wageningen University, P.O. Box 8129, 6700 EV Wageningen, The Netherlands
| | - Loes A. M. Mol
- Laboratory of Food Chemistry, Wageningen University, P.O. Box 8129, 6700 EV Wageningen, The Netherlands
| | - Susan A. M. The
- Laboratory of Food Chemistry, Wageningen University, P.O. Box 8129, 6700 EV Wageningen, The Netherlands
| | - Toine F. H. Bovee
- Department of Safety and Health, RIKILT-Institute of Food Safety, P.O. Box 230, 6700 AE Wageningen, The Netherlands
| | | | | | - Harry Gruppen
- Laboratory of Food Chemistry, Wageningen University, P.O. Box 8129, 6700 EV Wageningen, The Netherlands
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18
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Rachner TD, Benad P, Rauner M, Goettsch C, Singh SK, Schoppet M, Hofbauer LC. Osteoprotegerin production by breast cancer cells is suppressed by dexamethasone and confers resistance against TRAIL-induced apoptosis. J Cell Biochem 2009; 108:106-16. [DOI: 10.1002/jcb.22232] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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19
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Spink BC, Bennett JA, Pentecost BT, Lostritto N, Englert NA, Benn GK, Goodenough AK, Turesky RJ, Spink DC. Long-term estrogen exposure promotes carcinogen bioactivation, induces persistent changes in gene expression, and enhances the tumorigenicity of MCF-7 human breast cancer cells. Toxicol Appl Pharmacol 2009; 240:355-66. [PMID: 19619570 DOI: 10.1016/j.taap.2009.07.013] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2009] [Revised: 07/14/2009] [Accepted: 07/15/2009] [Indexed: 12/21/2022]
Abstract
The cumulative exposure to estrogens is an important determinant in the risk of breast cancer, yet the full range of mechanisms involving estrogens in the genesis and progression of breast cancer remains a subject of debate. Interactions of estrogens and environmental toxicants have received attention as putative factors contributing to carcinogenesis. Mechanistic studies have demonstrated interactions between estrogen receptor alpha (ERalpha) and the aryl hydrocarbon receptor (AhR), with consequences on the genes that they regulate. Many studies of ERalpha and AhR-mediated effects and crosstalk between them have focused on the initial molecular events. In this study, we investigated ERalpha- and AhR-mediated effects in long-term estrogen exposed (LTEE) MCF-7 human breast cancer cells, which were obtained by continuous culturing for at least 12 weeks in medium supplemented with 1 nM of 17beta-estradiol (E(2)). With these LTEE cells and with parallel control cells cultured without E(2) supplementation, we performed an extensive study of cytochrome P450 (CYP) induction, carcinogen bioactivation, global gene expression, and tumorigenicity in immunocompromised mice. We found that LTEE cells, in comparison with control cells, had higher levels of AhR mRNA and protein, greater responsiveness for AhR-regulated CYP1A1 and CYP1B1 induction, a 6-fold higher initial level of benzo(a)pyrene-DNA adducts as determined by liquid chromatography tandem mass spectrometry, marked differences in the expression of numerous genes, and a higher rate of E(2)-dependent tumor growth as xenografts. These studies indicate that LTEE causes adaptive responses in MCF-7 cells, which may reflect processes that contribute to the overall carcinogenic effect of E(2).
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Affiliation(s)
- Barbara C Spink
- Laboratory of Molecular Toxicology, Wadsworth Center, New York State Department of Health, Albany, NY 12201-0509, USA.
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20
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Rachner TD, Singh SK, Schoppet M, Benad P, Bornhäuser M, Ellenrieder V, Ebert R, Jakob F, Hofbauer LC. Zoledronic acid induces apoptosis and changes the TRAIL/OPG ratio in breast cancer cells. Cancer Lett 2009; 287:109-16. [PMID: 19577359 DOI: 10.1016/j.canlet.2009.06.003] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2009] [Revised: 05/29/2009] [Accepted: 06/04/2009] [Indexed: 01/06/2023]
Abstract
Breast cancer has a propensity to metastasize to bone, thus causing pathological fractures. Bisphosphonates are established drugs in the treatment of bone metastasis that inhibit osteoclast activity and interrupt the vicious cycle of osteoclast-tumor cell interactions. We evaluated the direct effects of zoledronic acid on estrogen receptor (ER)-negative MDA-MB-231 and ER-positive MCF-7 breast cancer cells. While zoledronic acid (100 microM) inhibited MDA-MB-231 cell proliferation after 72 h, and induced apoptosis via activation of caspase-3 and -7, it had only minor effects on MCF-7 cells. In addition, zoledronic acid induced apoptosis by up-regulating TNF-related apoptosis-inducing ligand (TRAIL) in MDA-MB-231 cells (p<0.01), but had no effect on the expression of its decoy receptor osteoprotegerin (OPG). In MCF-7 cells, both cytokines were suppressed by zoledronic acid. In conclusion, zoledronic acid enhanced the TRAIL-to-OPG ratio in TRAIL-sensitive MDA-MB-231 cells, indicating that the TRAIL/OPG cytokine system is a bisphosphonate-responsive target in breast cancer.
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Affiliation(s)
- Tilman D Rachner
- Division of Gastroenterology and Endocrinology, Department of Medicine, Philipps-University, Marburg, Germany
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21
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Ang EZF, Nguyen HT, Sim HL, Putti TC, Lim LHK. Annexin-1 regulates growth arrest induced by high levels of estrogen in MCF-7 breast cancer cells. Mol Cancer Res 2009; 7:266-74. [PMID: 19208747 DOI: 10.1158/1541-7786.mcr-08-0147] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Estrogen, a naturally occurring female steroid growth hormone, has been implicated as a major risk factor for the development of breast cancer. Recent research into this disease has also correlated Annexin-1 (ANXA1), a glucocorticoid-inducible protein, with the development of breast tumorigenesis. ANXA1 is lost in many cancers, including breast cancer, and this may result in a functional promotion of tumor growth. In this study, we investigated the expression of ANXA1 in MCF-7 cells treated with estrogen and the regulation of estrogen functions by ANXA1. Exposure of MCF-7 breast cancer cells to high physiologic levels (up to 100 nmol/L) of estrogen leads to an up-regulation of ANXA1 expression partially through the activation of cyclic AMP-responsive element binding protein and dependency on activation of the estrogen receptor. In addition, treatment of MCF-7 cells with physiologic levels of estrogen (1 nmol/L) induced proliferation, whereas high pregnancy levels of estrogen (100 nmol/L) induced a growth arrest of MCF-7 cells, associated with constitutive activation of extracellular signal-regulated kinase 1/2 and up-regulation of cell cycle arrest proteins such as p21(waf/cip). Silencing of ANXA1 with specific small interfering RNA reverses the estrogen-dependent proliferation as well as growth arrest and concomitantly modulates extracellular signal-regulated kinase 1/2 phosphorylation. We confirm that ANXA1 is lost in clinical breast cancer, indicating that the antiproliferative protective function of ANXA1 against high levels of estrogen may be lost. Finally, we show that ANXA1-deficient mice exhibit faster carcinogen-induced tumor growth. Our data suggest that ANXA1 may act as a tumor suppressor gene and modulate the proliferative functions of estrogens.
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Affiliation(s)
- Emily Zhao-Feng Ang
- Department of Physiology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore
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22
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Lønning PE. Endocrine therapy and bone loss in breast cancer: time to close in the RANK(L)? J Clin Oncol 2008; 26:4859-61. [PMID: 18725646 DOI: 10.1200/jco.2008.18.0851] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
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23
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Cheng C, Tsai HR. Analysis of steroids in yeast-mediated cell culture by on-line solid-phase extraction coupled high-performance liquid chromatography electrospray-ionization/mass spectrometry and novel continuous postcolumn infusion of internal standard technique. Anal Chim Acta 2008; 623:168-77. [DOI: 10.1016/j.aca.2008.06.012] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2008] [Revised: 06/11/2008] [Accepted: 06/11/2008] [Indexed: 10/21/2022]
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