27-hydroxycholesterol is an endogenous selective estrogen receptor modulator.
ABSTRACT: Selective estrogen receptor (ER) modulators (SERMs) are ER ligands whose relative agonist/antagonist activities vary in a cell- and promoter-dependent manner. The molecular basis underlying this selectivity can be attributed to the ability of these ligands to induce distinct alterations in ER structure leading to differential recruitment of coactivators and corepressors. Whether SERM activity is restricted to synthetic ligands or whether molecules exist in vivo that function in an analogous manner remains unresolved. However, the recent observation that oxysterols bind ER and antagonize the actions of 17beta-estradiol (E2) on the vascular wall suggests that this class of ligands may possess SERM activity. We demonstrate here that 27-hydroxycholesterol (27HC), the most prevalent oxysterol in circulation, functions as a SERM, the efficacy of which varies when assessed on different endpoints. Importantly, 27HC positively regulates both gene transcription and cell proliferation in cellular models of breast cancer. Using combinatorial peptide phage display, we have determined that 27HC induces a unique conformational change in both ERalpha and ERbeta, distinguishing it from E2 and other SERMs. Thus, as with other ER ligands, it appears that the unique pharmacological activity of 27HC relates to its ability to impact ER structure and modulate cofactor recruitment. Cumulatively, these data indicate that 27HC is an endogenous SERM with partial agonist activity in breast cancer cells and suggest that it may influence the pathology of breast cancer. Moreover, given the product-precursor relationship between 27HC and cholesterol, our findings have implications with respect to breast cancer risk in obese/hypercholesteremic individuals.
Project description:A series of triphenylethylene bisphenol analogues of the selective estrogen receptor modulator (SERM) tamoxifen were synthesized and evaluated for their abilities to inhibit aromatase, bind to estrogen receptor α (ER-α) and estrogen receptor β (ER-β), and antagonize the activity of β-estradiol in MCF-7 human breast cancer cells. The long-range goal has been to create dual aromatase inhibitor (AI)/selective estrogen receptor modulators (SERMs). The hypothesis is that in normal tissue the estrogenic SERM activity of a dual AI/SERM could attenuate the undesired effects stemming from global estrogen depletion caused by the AI activity of a dual AI/SERM, while in breast cancer tissue the antiestrogenic SERM activity of a dual AI/SERM could act synergistically with AI activity to enhance the antiproliferative effect. The potent aromatase inhibitory activities and high ER-α and ER-β binding affinities of several of the resulting analogues, together with the facts that they antagonize β-estradiol in a functional assay in MCF-7 human breast cancer cells and they have no E/Z isomers, support their further development in order to obtain dual AI/SERM agents for breast cancer treatment.
Project description:PURPOSE:27-hydroxycholesterol (27HC), an endogenous selective estrogen receptor modulator (SERM), drives the growth of estrogen receptor-positive (ER+) breast cancer. 1,25-dihydroxyvitamin D (1,25(OH)2D), the active metabolite of vitamin D, is known to inhibit expression of CYP27B1, which is very similar in structure and function to CYP27A1, the synthesizing enzyme of 27HC. Therefore, we hypothesized that 1,25(OH)2D may also inhibit expression of CYP27A1, thereby reducing 27HC concentrations in the blood and tissues that express CYP27A1, including breast cancer tissue. METHODS:27HC, 25-hydroxyvitamin D (25OHD), and 1,25(OH)2D were measured in sera from 29 breast cancer patients before and after supplementation with low-dose (400 IU/day) or high-dose (10,000 IU/day) vitamin D in the interval between biopsy and surgery. RESULTS:A significant increase (p = 4.3E-5) in 25OHD and a decrease (p = 1.7E-1) in 27HC was observed in high-dose versus low-dose vitamin D subjects. Excluding two statistical outliers, 25OHD and 27HC levels were inversely correlated (p = 7.0E-3). CONCLUSIONS:Vitamin D supplementation can decrease circulating 27HC of breast cancer patients, likely by CYP27A1 inhibition. This suggests a new and additional modality by which vitamin D can inhibit ER+ breast cancer growth, though a larger study is needed for verification.
Project description:The majority of breast cancers express the estrogen receptor and depend on estradiol (E2) for their growth. Hormonal therapy aims at depriving estrogen signaling either by using selective estrogen receptor modulators (SERM)-that interfere with the binding of E2 to its receptor (ER)-or aromatase inhibitors (AI)-that block the aromatase-dependent synthesis of E2. While SERMs are recommended for both pre- and post-menopausal patients, AIs are indicated only for post-menopausal patients. For the past 20 years, the SERM tamoxifen has been considered the "gold standard" for the treatment of hormone receptor positive breast cancers. However, tamoxifen's role is now challenged by third generation AIs, such as anastrozole, which exhibit greater efficacy in the adjuvant setting in several recently reported trials. This review will focus on anastrozole's mechanism of action, dosing, pharmacology, pharmacokinetics, and clinical applications. It will briefly discuss the clinical trials that determined anastrozole's efficacy in the treatment of advanced breast cancer (ABC) and in the neoadjuvant setting. Finally, it will present the clinical trials that established anastrozole as a frontline agent in the treatment of post-menopausal women with hormone receptor positive early breast cancer.
Project description:There is compelling evidence to suggest that drugs that function as pure estrogen receptor (ER-?) antagonists, or that downregulate the expression of ER-?, would have clinical use in the treatment of advanced tamoxifen- and aromatase-resistant breast cancer. Although such compounds are currently in development, we reasoned, based on our understanding of ER-? pharmacology, that there may already exist among the most recently developed selective estrogen receptor modulators (SERM) compounds that would have usage as breast cancer therapeutics. Thus, our objective was to identify among available SERMs those with unique pharmacologic activities and to evaluate their potential clinical use with predictive models of advanced breast cancer.A validated molecular profiling technology was used to classify clinically relevant SERMs based on their impact on ER-? conformation. The functional consequences of these observed mechanistic differences on (i) gene expression, (ii) receptor stability, and (iii) activity in cellular and animal models of advanced endocrine-resistant breast cancer were assessed.The high-affinity SERM bazedoxifene was shown to function as a pure ER-? antagonist in cellular models of breast cancer and effectively inhibited the growth of both tamoxifen-sensitive and -resistant breast tumor xenografts. Interestingly, bazedoxifene induced a unique conformational change in ER-? that resulted in its proteasomal degradation, although the latter activity was dispensable for its antagonist efficacy.Bazedoxifene was recently approved for use in the European Union for the treatment of osteoporosis and thus may represent a near-term therapeutic option for patients with advanced breast cancer.
Project description:Breast cancer remains a significant cause of death in women, and few therapeutic options exist for estrogen receptor negative (ER?(-)) cancers. Epigenetic reactivation of target genes using histone deacetylase (HDAC) inhibitors has been proposed in ER?(-) cancers to resensitize to therapy using selective estrogen receptor modulators (SERMs) that are effective in ER?(+) cancer treatment. Based upon preliminary studies in ER?(+) and ER?(-) breast cancer cells treated with combinations of HDAC inhibitors and SERMs, hybrid drugs, termed SERMostats, were designed with computational guidance. Assay for inhibition of four type?I HDAC isoforms and antagonism of estrogenic activity in two cell lines yielded a SERMostat with 1-3??M potency across all targets. The superior hybrid caused significant cell death in ER?(-) human breast cancer cells and elicited cell death at the same concentration as the parent SERM in combination treatment and at an earlier time point.
Project description:The estrogen signaling pathway has been reported to modulate prostate cancer (PCa) progression through the activity of estrogen receptors ? and ? (ER? and ER?). Given that selective estrogen receptor modulators (SERMs) are used to treat breast cancer, ERs have been proposed as attractive therapeutic targets in PCa. However, many inconsistencies regarding the expression of ERs and the efficacy of SERMs for PCa treatment exist, notably due to the use of ER? antibodies lacking specificity and treatments with high SERM concentrations leading to off-target effects. To end this confusion, our objective was to study the impact of estrogenic and anti-estrogenic ligands in well-studied in vitro PCa models with appropriate controls, dosages, and ER subtype-specific antibodies. When using physiologically relevant concentrations of nine estrogenic/anti-estrogenic compounds, including five SERMs, we observed no significant modulation of PCa cell proliferation. Using RNA-seq and validated antibodies, we demonstrate that these PCa models do not express ERs. In contrast, RNA-seq from PCa samples from patients have detectable expression of ER?. Overall, our study reveals that commonly used PCa models are inappropriate to study ERs and indicate that usage of alternative models is essential to properly assess the roles of the estrogen signaling pathway in PCa.
Project description:The clinical benzothiophene SERM (BT-SERM), raloxifene, was compared with estrogens in protection of primary rat neurons against oxygen-glucose deprivation (OGD). Structure-activity relationships for neuroprotection were determined for a family of BT-SERMs displaying a spectrum of ER? and ER? binding affinity and agonist/antagonist activity, leading to discovery of a neuroprotective pharmacophore, present in the clinically relevant SERMS, raloxifene and desmethylarzoxifene (DMA), for which submicromolar potency was observed for neuroprotection. BT-SERM neuroprotection did not correlate with binding to ER nor classical ER activity, however, both the neuroprotective SERMs and estrogens were shown, using pharmacological probes, to activate the same kinase signaling cascades. The antiestrogen ICI 182,780 inhibited the actions of estrogens, but not those of BT-SERMs, whereas antagonism of the G-protein coupled receptor, GPR30, was effective for both SERMs and estrogens. Since SERMs have antioxidant activity, ER-independent mechanisms were studied using the classical phenolic antioxidants, BHT and Trolox, and the Nrf2-dependent cytoprotective electrophile, sulforaphane. However, neuroprotection by these agents was not sensitive to GPR30 antagonism. Collectively, these data indicate that the activity of neuroprotective BT-SERMs is GPR30-dependent and ER-independent and not mediated by antioxidant effects. Comparison of novel BT-SERM derivatives and analogs identified a neuroprotective pharmacophore of potential use in design of novel neuroprotective agents with a spectrum of ER activity.
Project description:BACKGROUND:We previously performed a case-control genome-wide association study in women treated with selective estrogen receptor modulators (SERMs) for breast cancer prevention and identified single nucleotide polymorphisms (SNPs) in ZNF423 as potential biomarkers for response to SERM therapy. The ZNF423rs9940645 SNP, which is approximately 200 bp away from the estrogen response elements, resulted in the SNP, estrogen, and SERM-dependent regulation of ZNF423 expression and, "downstream", that of BRCA1. METHODS:Electrophoretic mobility shift assay-mass spectrometry was performed to identify proteins binding to the ZNF423 SNP and coordinating with estrogen receptor alpha (ER?). Clustered, regularly interspaced short palindromic repeats (CRISPR)/Cas9 genome editing was applied to generate ZR75-1 breast cancer cells with different ZNF423 SNP genotypes. Both cultured cells and mouse xenograft models with different ZNF423 SNP genotypes were used to study the cellular responses to SERMs and poly(ADP-ribose) polymerase (PARP) inhibitors. RESULTS:We identified calmodulin-like protein 3 (CALML3) as a key sensor of this SNP and a coregulator of ER?, which contributes to differential gene transcription regulation in an estrogen and SERM-dependent fashion. Furthermore, using CRISPR/Cas9-engineered ZR75-1 breast cancer cells with different ZNF423 SNP genotypes, striking differences in cellular responses to SERMs and PARP inhibitors, alone or in combination, were observed not only in cells but also in a mouse xenograft model. CONCLUSIONS:Our results have demonstrated the mechanism by which the ZNF423 rs9940645 SNP might regulate gene expression and drug response as well as its potential role in achieving more highly individualized breast cancer therapy.
Project description:The cholesterol metabolite and SERM, 27HC, is the signaling molecule that links cholesterol to breast cancer pathophysiology Hypercholesterolemia is a risk factor for breast cancer, and patients taking statins demonstrate lower breast cancer incidence and decreased breast cancer recurrence, data that highlights the potential importance of the recent finding that 27-Hydroxycholesterol (27HC), a primary metabolite of cholesterol, acts as a selective estrogen receptor modulator (SERM). The goal of this study was to evaluate the impact of 27HC on breast cancer pathophysiology. Elevation of 27HC in murine models increased tumor growth in an estrogen receptor dependent manner. Importantly, a high cholesterol diet decreased the time to tumor onset and increased tumor growth, and this response required presence of CYP27A1. Within human breast cancer samples, CYP27A1 expression increasesd with grade, in addition to being highly expressed in tumor associated macrophages. Finally 27HC increases metastasis to the lung. The findings herein strongly support a role for 27HC in breast cancer pathophysiology, providing support for the exploration of potential chemopreventative benefits of lower cholesterol diets, and pharmacological inhibitors of HMG-CoA reductase or CYP27A1. MCF-7 cells were treated as indicated in the presence of E2 or vehicle; RNA was isolated and used for preparation of label for 3' expression analysis.
Project description:Selective estrogen receptor modulators (SERMs), such as tamoxifen (TAM), have been used extensively for the treatment and prevention of breast cancer and other pathologies associated with aberrant estrogen receptor (ER) signaling. These compounds exhibit cell-selective agonist/antagonist activities as a consequence of their ability to induce different conformational changes in ER, thereby enabling it to recruit functionally distinct transcriptional coregulators. However, the observation that SERMs can also regulate aspects of calcium signaling and apoptosis in an ER-independent manner in some systems suggests that some of the activity of drugs within this class may also arise as a consequence of their ability to interact with targets other than ER. In this study, we demonstrate that 4-hydroxy-TAM (4OHT), an active metabolite of TAM, directly binds to and modulates the transcriptional activity of the aryl hydrocarbon receptor (AHR). Of specific interest was the observation, that in the absence of ER, 4OHT can induce the expression of AHR target genes involved in estradiol metabolism, cellular proliferation, and metastasis in cellular models of breast cancer. The potential role for AHR in SERM pharmacology was further underscored by the ability of 4OHT to suppress osteoclast differentiation in vitro in part through AHR. Cumulatively, these findings provide evidence that it is necessary to reevaluate the relative roles of ER and AHR in manifesting the pharmacological actions and therapeutic efficacy of TAM and other SERMs.