Structure-Activity Relationship of para-Carborane Selective Estrogen Receptor ß Agonists.

Selective agonism of the estrogen receptor (ER) subtypes, ERα and ERß, has historically been difficult to achieve due to the high degree of ligand-binding domain structural similarity. Multiple efforts have focused on the use of classical organic scaffolds to model 17ß-estradiol geometry in the design of ERß selective agonists, with several proceeding to various stages of clinical development. Carborane scaffolds offer many unique advantages including the potential for novel ligand/receptor interactions but remain relatively unexplored. We synthesized a series of para-carborane estrogen receptor agonists revealing an ERß selective structure-activity relationship. We report ERß agonists with low nanomolar potency, greater than 200-fold selectivity for ERß over ERα, limited off-target activity against other nuclear receptors, and only sparse CYP450 inhibition at very high micromolar concentrations. The pharmacological properties of our para-carborane ERß selective agonists measure favorably against clinically developed ERß agonists and support further evaluation of carborane-based selective estrogen receptor modulators.

Binding Assays Using a Benzofurazan-Labeled Fluorescent Probe for Estrogen Receptor-Ligand Interactions.

Binding assays are widely used to study the estrogenic activity of compounds targeting the estrogen receptor (ER). The fluorescence properties of benzofurazan (BD), an environmentally sensitive fluorophore, are affected by solvent polarity. In this study, we synthesized BD-labeled estradiol (E2) derivatives hoping to develop a fluorescent ligand to be used in ER binding assays, without the separation of free- from bound-ligand. Three fluorescent ligands with a BD skeleton were obtained and their fluorescence properties were investigated. Analysis of the fluorescent ligands and human recombinant ERα (hr-ERα) interactions revealed that the fluorescence intensity increased in hydrophobic environments, such as the receptor-binding site. In saturation binding assays, ABD-E2 derivative 2c showed positive cooperative binding, and its dissociation constant (Kd) and Hill coefficient were 23.4 nM and 1.34, respectively. The estrogenic compounds affinity, assessed by competitive binding assays was well correlated with the results obtained by conventional studies, using the fluorescence polarization method. Overall, the developed assay using BD-labeled ligands was a simple, rapid, and reliable method for the evaluation of ER binding affinity.

Synthesis and evaluation of 17α-triazolyl and 9α-cyano derivatives of estradiol.

A variety of 17α-triazolyl and 9α-cyano derivatives of estradiol were prepared and evaluated for binding to human ERß in both a TR-FRET assay, as well as ERß and ERα agonism in cell-based functional assays. 9α-Cyanoestradiol (5) was nearly equipotent as estradiol as an agonist for both ERß and ERα. The potency of the 17α-triazolylestradiol analogs is considerably more variable and depends on the nature of the 4-substituent of the triazole ring. While rigid protein docking simulations exhibited significant steric clashing, induced fit docking providing more protein flexibility revealed that the triazole linker of analogs 2d and 2e extends outside of the traditional ligand binding domain with the benzene ring located in the loop connecting helix 11 to helix 12.

Pharmacology and Molecular Mechanisms of Clinically Relevant Estrogen Estetrol and Estrogen Mimic BMI-135 for the Treatment of Endocrine-Resistant Breast Cancer.

Long-term estrogen deprivation (LTED) with tamoxifen (TAM) or aromatase inhibitors leads to endocrine-resistance, whereby physiologic levels of estrogen kill breast cancer (BC). Estrogen therapy is effective in treating patients with advanced BC after resistance to TAM and aromatase inhibitors develops. This therapeutic effect is attributed to estrogen-induced apoptosis via the estrogen receptor (ER). Estrogen therapy can have unpleasant gynecologic and nongynecologic adverse events. Here, we study estetrol (E4) and a model Selective Human ER Partial Agonist (ShERPA) BMI-135. Estetrol and ShERPA TTC-352 are being evaluated in clinical trials. These agents are proposed as safer estrogenic candidates compared with 17ß-estradiol (E2) for the treatment of endocrine-resistant BC. Cell viability assays, real-time polymerase chain reaction, luciferase reporter assays, chromatin immunoprecipitation, docking and molecular dynamics simulations, human unfolded protein response (UPR) RT2 PCR profiler arrays, live cell microscopic imaging and analysis, and annexin V staining assays were conducted. Our work was done in eight biologically different human BC cell lines and one human endometrial cancer cell line, and results were compared with full agonists estrone, E2, and estriol, a benchmark partial agonist triphenylethylene bisphenol (BPTPE), and antagonists 4-hydroxytamoxifen and endoxifen. Our study shows the pharmacology of E4 and BMI-135 as less-potent full-estrogen agonists as well as their molecular mechanisms of tumor regression in LTED BC through triggering a rapid UPR and apoptosis. Our work concludes that the use of a full agonist to treat BC is potentially superior to a partial agonist given BPTPE's delayed induction of UPR and apoptosis, with a higher probability of tumor clonal evolution and resistance. SIGNIFICANCE STATEMENT: Given the unpleasant gynecologic and nongynecologic adverse effects of estrogen treatment, the development of safer estrogens for endocrine-resistant breast cancer (BC) treatment and hormone replacement therapy remains a priority. The naturally occurring estrogen estetrol and Selective Human Estrogen-Receptor Partial Agonists are being evaluated in endocrine-resistant BC clinical trials. This work provides a comprehensive evaluation of their pharmacology in numerous endocrine-resistant BC models and an endometrial cancer model and their molecular mechanisms of tumor regression through the unfolded protein response and apoptosis.

Neurodevelopmental effects of natural and synthetic ligands of estrogen and progesterone receptors in zebrafish eleutheroembryos.

Natural and synthetic estrogens and progestins are widely used in human and veterinary medicine and are detected in waste and surface waters. Our previous studies have clearly shown that a number of these substances targets the brain to induce the estrogen-regulated brain aromatase expression but the consequences on brain development remain virtually unexplored. The aim of the present study was therefore to investigate the effect of estradiol (E2), progesterone (P4) and norethindrone (NOR), a 19-nortestosterone progestin, on zebrafish larval neurogenesis. We first demonstrated using real-time quantitative PCR that nuclear estrogen and progesterone receptor brain expression is impacted by E2, P4 and NOR. We brought evidence that brain proliferative and apoptotic activities were differentially affected depending on the steroidal hormone studied, the concentration of steroids and the region investigated. Our findings demonstrate for the first time that steroid compounds released in aquatic environment have the capacity to disrupt key cellular events involved in brain development in zebrafish embryos further questioning the short- and long-term consequences of this disruption on the physiology and behavior of organisms.

Bisphenol AF: Halogen bonding effect is a major driving force for the dual ERα-agonist and ERß-antagonist activities.

17ß-Estradiol (E2) is a natural steroid ligand for the structurally and physiologically independent estrogen receptors (ERs) ERα and ERß. We recently observed that CF3-containing bisphenol AF (BPAF) works as an agonist for ERα but as an antagonist for ERß. Similar results were also observed for the CCl3-containing bisphenol designated as HPTE. Both BPAF and HPTE are comprised of a tri-halogenated methyl group in the central alkyl moiety of their bisphenol structures, which strongly suggests that halogens contribute directly to the agonist/antagonist dual biological functions. We conducted this study to investigate the structure-activity relationships by assessing together newly synthesized CF3- and CBr3-containing bisphenol E analogs (BPE-X). We first tested bisphenols for their receptor binding ability and then for their transcriptional activities. Halogen-containing bisphenols were found to be fully active for ERα, but almost completely inactive for ERß. When we examined these bisphenols for their inhibitory activities for E2 in ERß, we observed that they worked as distinct antagonists. The ascending order of agonist/antagonist dual biological functions was BPE-F < BPE-Cl (HPTE) ≤ BPAF < BPE-Br, demonstrating that the electrostatic halogen bonding effect is a major driving force of the bifunctional ERα agonist and ERß antagonist activities of BPAF.

Design, Synthesis, Anticancer Evaluation and Molecular Modeling of Novel Estrogen Derivatives.

A series of estrone derivatives 3⁻8 was designed and synthesized using estrone arylmethylenes 2a,b as starting materials and their structures were confirmed by different spectral data and elemental analyses. All the newly synthesized compounds exhibited potent in vitro and in vivo cytotoxic activities against breast cancer cell lines. In addition, all compounds were subjected to in vitro and in vivo inhibition assays for EGFR and VEGFR-2 kinases as well as p53 ubiquitination activity to obtain more details about their mechanism of action. Based on the promising results, a molecular docking study was investigated for the most representative compound 5a against the two targets, EGFR and VEGFR-2 kinases, to assess its binding affinity, hoping to rationalize and obtain potent anticancer agents in the future.

Discovery of Potent, Selective, and Orally Bioavailable Estrogen-Related Receptor-γ Inverse Agonists To Restore the Sodium Iodide Symporter Function in Anaplastic Thyroid Cancer.

An inverse agonist of estrogen-related receptor-γ (ERRγ), an orphan nuclear receptor encoded by E srrg, enhances sodium iodide symporter-mediated radioiodine uptake in anaplastic thyroid cancer (ATC) cells, thereby facilitating responsiveness to radioiodine therapy in vitro. We synthesized potent, selective, and orally bioavailable ERRγ-inverse agonists and evaluated their activity by analyzing in vitro pharmacology and absorption, distribution, metabolism, excretion, and toxicity profiles. X-ray crystallographic analysis of the ligand and ERRγ complex showed that 35 completely binds to the target protein (PDB 6A6K ). Our results showed improved radioiodine avidity in ATC cells through compound 35-mediated upregulation of iodide-handling genes, leading to enhanced responsiveness to radioiodine therapy in vitro. Importantly, in vivo 124I-positron emission tomography/computed tomography imaging revealed that 35 increases radioiodine avidity in CAL62 tumors. Collectively, these results demonstrated that 35 can be developed as a promising treatment for ERRγ-related cancer in the future.

Synthesis and evaluation of 4-cycloheptylphenols as selective Estrogen receptor-ß agonists (SERBAs).

A short and efficient route to 4-(4-hydroxyphenyl)cycloheptanemethanol was developed, which resulted in the preparation of a mixture of 4 stereoisomers. The stereoisomers were separated by preparative HPLC, and two of the stereoisomers identified by X-ray crystallography. The stereoisomers, as well as a small family of 4-cycloheptylphenol derivatives, were evaluated as estrogen receptor-beta agonists. The lead compound, 4-(4-hydroxyphenyl)cycloheptanemethanol was selective for activating ER relative to seven other nuclear hormone receptors, with 300-fold selectivity for the ß over α isoform and with EC50 of 30-50 nM in cell-based and direct binding assays.

3,20-Dihydroxy-13α-19-norpregna-1,3,5(10)-trienes. Synthesis, structures, and cytotoxic, estrogenic, and antiestrogenic effects.

New 3,20-dihydroxy-13α-19-norpregna-1,3,5(10)-trienes were synthesized. The effects of these compounds on breast cancer cells and ERα activation were investigated. The scaffold of compounds containing the six-membered ring D' annulated at 16α,17α-positions was constructed via the Lewis acid catalyzed Diels-Alder reaction of butadiene with 3-methoxy-13α-19-norpregna-1,3,5(10),16-tetraen-20-one 5 under a pressure of 600 MPa. The hydrogenation of primary cyclohexene adduct 6 followed by the one-pot reduction-demethylation (DIBAH) gave target epimeric 3,20-dihydroxy steroids 8a and 8b. The Corey-Chaykovsky reaction of the same conjugated ketone 5 gave a 16α,17α-methylene-substituted compound. The reaction of the latter with DIBAH yielded 3,20(R,S)-dihydroxy-16α,17α-methyleno-13α-19-norpregna-1,3,5(10)-triene 10. The hydrogenation of the 16,17-double bond of compound 5 produced a mixture of 17α- and 17ß-epimeric ketones, reduction-demethylation of which gave 3,20(S)-dihydroxy-13α,17α-19-norpregna-1,3,5(10)-triene 12a and 3,20(R)-dihydroxy-13α,17ß-19-norpregna-1,3,5(10)-triene 12b. All compounds were fully characterized by 1D and 2D NMR, HRMS, and X-ray diffraction. All target compounds showed pronounced cytotoxic effect against MCF-7 breast cancer cells and NCI/ADR-RES doxorubicin-resistant cells at micromolar concentrations. The ERα-mediated luciferase reporter gene assay demonstrated that all compounds, except for compound 10, are ERα inhibitors, while cyclopropane compound 10 proved to be an ERα activator. Docking experiments showed that all compounds are well accommodated to LBD ERα but have some differences in the binding mode.

Influência da neoplasia mamária na concentração sérica de hormônios e na expressão de receptores de estrógeno e progesterona em cadelas / Influence of mammary neoplasm on the serum concentration of hormones and on the expression of estrogen and progesterone receptors in bitches

O objetivo desse estudo foi avaliar as concentrações séricas de estradiol, progesterona e prolactina, bem como a expressão gênica dos receptores de estrógeno α e β e de progesterona em cadelas com neoplasias mamárias. Foram utilizadas 60 cadelas adultas, sem raça definida que foram distribuídas em dois grupos. O Grupo I constituído por 30 cadelas portadoras de neoplasias mamárias e o Grupo II constituído por 30 cadelas saudáveis, não portadoras de neoplasia. Para os tutores, foram aplicados questionários sobre fatores epidemiológicos da doença. Após avaliação dos exames pré-operatórios, as cadelas com neoplasia mamária foram submetidas à mastectomia, coletaram-se fragmentos das neoplasias e linfonodos regionais, os quais foram processados para análise histopatológica. Para as dosagens hormonais de estradiol, progesterona e prolactina foram colhidas amostras de sangue em tubos sem anticoagulante e os soros foram submetidos à técnica de eletroquimioluminescência. A expressão gênica dos receptores hormonais foi realizada por meio da técnica de Real-time PCR e para isso foram coletados fragmentos das neoplasias mamárias e extraído o RNA para obtenção do cDNA. A expressão do mRNA para os REα, REβ e RP foi avaliada a partir da amplificação desses genes utilizando primers específicos. Verificaram-se maiores níveis séricos de estradiol (média de 38,98±13,68pg/mL) em cadelas portadoras de neoplasias mamárias malignas quando comparadas as cadelas do grupo controle (p<0,05). Já os níveis séricos de prolactina foram maiores (média de 0,231±0,201ng/mL) nas cadelas que não possuíam neoplasias mamárias quando comparadas ao Grupo I (p<0,05). Para os níveis de progesterona não foram observadas diferença entre os diferentes grupos (p>0,05). Tanto os tumores malignos como os benignos expressaram REα, REβ e RP, não havendo diferença (p>0,05) na expressão entre tumores malignos ou benignos ou relacionada aos outros fatores prognósticos investigados (estadiamento clínico, presença de ulceração, vascularização e tempo de evolução do processo). Os níveis séricos de estradiol aumentaram significativamente com o estadiamento clínico da doença (p<0,05). Verificou-se moderada correlação negativa entre os níveis séricos de estradiol e prolactina. Dessa forma, conclui-se que as dosagens séricas de estradiol e PRL foram influenciadas pela malignidade do tumor e pelo estadiamento clínico das neoplasias. Os receptores hormonais foram expressos pelas neoplasias, independentemente do tipo tumoral e não estão associados aos outros fatores prognóstico clássicos, como presença de ulceração, vascularização ou estadiamento clínico.(AU)

The aim of this study was to evaluate the serum concentrations of estradiol, progesterone, prolactin, the gene expression of estrogen α and β and progesterone receptors in bitches with mammary neoplasms. Sixty adult crossbred bitches distributed in two groups were used. Group I consisted of 30 bitches with mammary neoplasms and Group II consisted of 30 healthy bitches without neoplasia. For the tutors, interviews were made about the disease epidemiology. After preoperative examinations, bitches with mammary neoplasia were submitted to mastectomy; fragments of the neoplasms and regional lymph nodes were collected and processed for histopathological analysis. Blood samples were collected in tubes without anticoagulant and the serum was analyzed by electrochemiluminescence to measure estradiol, progesterone and prolactin. The gene expression of the hormonal receptors was performed by means of the Real-time PCR technique, thus fragments of mammary neoplasms were collected and the RNA was extracted to obtain cDNA. Expression of the mRNA for ERα, ERβ and PR was assessed from the amplification of these genes using specific primers. Higher serum levels of estradiol (mean 38.98±13.68pg/mL) were observed in bitches with malignant neoplasms when compared to the control bitches (p<0.05). Serum prolactin levels were higher (mean of 0.231±0.201ng/mL) in bitches that did not have mammary neoplasms when compared to Group I (p<0.05). No difference was observed for related to the progesterone levels between the groups (p>0.05). Both malignant and benign tumors expressed ERα, ERβ and RP with no statistical difference (p>0.05) and there were no difference related to the other prognostic factors investigated (clinical staging, presence of ulceration, vascularization and aging of neoplasms). Serum estradiol levels increased significantly with the clinical staging of the disease (p<0.05). There was a moderate negative correlation between serum levels of estradiol and prolactin. It was concluded that serum levels of estradiol and PRL were influenced by tumor malignancy and clinical staging of neoplasms. Hormonal receptors were expressed by neoplasms, regardless of tumor type and are not associated with other classical prognostic factors, such as ulceration, vascularization or clinical staging.(AU)

Design, synthesis, and evaluation of simple phenol amides as ERRγ agonists.

Herein we report the design and synthesis of a series of simple phenol amide ERRγ agonists based on a hydrazone lead molecule. Our structure activity relationship studies in this series revealed the phenol portion of the molecule to be required for activity. Attempts to replace the hydrazone with more suitable chemotypes led to a simple amide as a viable alternative. Differential hydrogen-deuterium exchange experiments were used to help understand the structural basis for binding to ERRγ and aid in the development of more potent ligands.

Synthesis of novel (-)-epicatechin derivatives as potential endothelial GPER agonists: Evaluation of biological effects.

To potentially identify proteins that interact (i.e. bind) and may contribute to mediate (-)-epicatechin (Epi) responses in endothelial cells we implemented the following strategy: 1) synthesis of novel Epi derivatives amenable to affinity column use, 2) in silico molecular docking studies of the novel derivatives on G protein-coupled estrogen receptor (GPER), 3) biological assessment of the derivatives on NO production, 4) implementation of an immobilized Epi derivative affinity column and, 5) affinity column based isolation of Epi interacting proteins from endothelial cell protein extracts. For these purposes, the Epi phenol and C3 hydroxyl groups were chemically modified with propargyl or mesyl groups. Docking studies of the novel Epi derivatives on GPER conformers at 14 ns and 70 ns demostrated favorable thermodynamic interactions reaching the binding site. Cultures of bovine coronary artery endothelial cells (BCAEC) treated with Epi derivatives stimulated NO production via Ser1179 phosphorylation of eNOS, effects that were attenuated by the use of the GPER blocker, G15. Epi derivative affinity columns yielded multiple proteins from BCAEC. Proteins were electrophoretically separated and inmmunoblotting analysis revealed GPER as an Epi derivative binding protein. Altogether, these results validate the proposed strategy to potentially isolate and identify novel Epi receptors that may account for its biological activity.

Regioselective monoalkylation of 17ß-estradiol for the synthesis of cytotoxic estrogens.

The regioselective synthesis of estrogens and their derivatives continues to be of interest. Most reported syntheses require multistep protocols associated with poor overall yield and lack of regioselectivity. New preparative protocols are still desired. Herein, 11 2-alkylated 17ß-estradiol analogs were synthesized in a highly regioselective manner. The products were obtained using a convenient, one pot and high-yielding protocol. The anti-proliferative activity of the compounds was tested in human T-cell leukemia (CEM), human cervix carcinoma (HeLa) and human dermal microvascular endothelial (HMEC-1) cells.

Design, synthesis, and biological evaluation of steroidal analogs as estrogenic/anti-estrogenic agents.

Series of estrone based analogs were synthetically investigated at positions C-9, C-11, C-16, and C-17 positions, to be biologically evaluated via assessment of cell proliferation, cytotoxicity, and estrogenic/anti-estrogenic activity. LA-7 and LA-10 revealed their potential to exhibit inhibitory estrogenic profile. This was further validated by Estrogen Receptor-α (ER-α) and Estrogen Receptor-ß (ER-ß) competitive binding assays to reveal the high selective affinity of LA-7 towards ER-α at 5.49µM, while LA-10 did not show any binding affinity towards neither ER-α nor ER-ß; suggesting another mechanism for inhibition. This was validated by in silico molecular docking simulations of LA-7 to reveal the optimum binding affinity of LA-7 towards ER-α.

Identification of Selective ERRγ Inverse Agonists.

GSK5182 (4) is currently one of the lead compounds for the development of estrogen-related receptor gamma (ERRγ) inverse agonists. Here, we report the design, synthesis, pharmacological and in vitro absorption, distribution, metabolism, excretion, toxicity (ADMET) properties of a series of compounds related to 4. Starting from 4, a series of analogs were structurally modified and their ERRγ inverse agonist activity was measured. A key pharmacophore feature of this novel class of ligands is the introduction of a heterocyclic group for A-ring substitution in the core scaffold. Among the tested compounds, several of them are potent ERRγ inverse agonists as determined by binding and functional assays. The most promising compound, 15g, had excellent binding selectivity over related subtypes (IC50 = 0.44, >10, >10, and 10 µM at the ERRγ, ERRα, ERRß, and ERα subtypes, respectively). Compound 15g also resulted in 95% transcriptional repression at a concentration of 10 µM, while still maintaining an acceptable in vitro ADMET profile. This novel class of ERRγ inverse agonists shows promise in the development of drugs targeting ERRγ-related diseases.

Synthesis, estrogenic activity, and anti-osteoporosis effects in ovariectomized rats of resveratrol oligomer derivatives.

Three series of resveratrol oligomer derivatives were synthesized, including the indenone-type, indene-type and octahydropentalene-type derivatives, among which ten derivatives were novel compounds. Compounds 2, 14f, and 4d were confirmed as ERß agonists by yeast two-hybrid assay, and compound 2 (isopaucifloral F) was further chosen to evaluate its anti-osteoporosis activity in vivo. Compared with the sham-operated and the positive control groups, isopaucifloral F (10 µg/kg) showed a notable anti-osteoporosis effect in the ovariectomized (OVX) female rats based on a micro-CT analysis and the following measurements: bone mineral density, bone volume/tissue volume, trabecular thickness, trabecular separation/spacing, and the serum biochemical parameters. LD50 of isopaucifloral F was found to be greater than 5 mg/kg and its effective dose (ED) was found to be about 10 µg/kg. Therefore, isopaucifloral F may be a promising lead compound for the treatment of postmenopausal osteoporosis.

Concise synthesis of 12a-methyl-11-aryl-1,2-dihydrobenzo[f]pyrrolo[1,2-a]quinolin-3(12aH)-ones as racemic 14-azaestrogen analogs.

A concise method for the synthesis of 14-azasteroid analogs with angular methyl group at C-13 of the steroidal nucleus has been reported in this paper. We have developed an interesting cascade reaction of arylacetylenes and N-(naphthalen-2-yl)pent-4-ynamides under gold (III)-catalysis to produce novel tetracyclic 12a-methyl-11-aryl-1,2-dihydrobenzo[f]pyrrolo[1,2-a]quinolin-3(12aH)-ones which may be viewed as 14-azaestrogen analogs.

Stereospecific cis- and trans-ring fusions arising from common intermediates.

Highly concise and stereospecific routes to cis and trans fusion, carrying various functionality at one of the bridgehead carbons, have been accomplished.

Design, synthesis, and biological evaluation of cyclopropyl analogues of stilbene with raloxifene side chain as subtype-selective ligands for estrogen receptor.

We have designed the cyclopropane analog of stilbene as subtype-selective ligands for estrogen receptor based on the bioisosterism that cyclopropane could act as alkene bioisoster. Three cyclopropane analogs were prepared efficiently starting from 4-benzyloxybenzaldehyde, and evaluated for their binding to estrogen receptors ERα and ERß. These cyclopropane analogs were also found to be full agonists in estrogen receptor-mediated gene transcription assay. Compared to the stilbene analogs such as tamoxifen and raloxifene, the three cyclopropane analogs showed lower binding affinity for estrogen receptor, but higher subtype selectivity for ERα. The structure-activity relationship revealed from this study might provide clues for improving subtype selectivity for ERα.