Selective Estrogen Receptor Modulator Tamoxifen Research Articles

Abstract P5-14-06: Towards breast cancer prevention through reduced breast density: Suppressive effects of tamoxifen on normal breast epithelial cells

Abstract Background: Breast density is positively associated with risk of breast cancer and the local microenvironment in the normal breast is known to significantly impact breast cancer initiation and further progression. The selective estrogen receptor modulator tamoxifen, with beneficial clinical effects on breast cancer recurrence, has also been shown to reduce mammographic density potentially explaining the primary preventive effects of tamoxifen. Still, important gaps persist regarding the cellular and molecular basis of how tamoxifen modifies breast density and subsequently breast cancer risk. Purpose: To investigate the impact by tamoxifen on normal human breast epithelial cells (MCF-10A) with the additional ambition to mimic variations in breast density on the cellular level. Experimental design: Effects of tamoxifen on MCF-10A cells at different cellular densities were evaluated in vitro. Flow cytometry and the sulforhodamine-B assay were used to assess cell cycle distribution and proliferation. Cell adhesion to extracellular matrix proteins was analyzed using hexosaminidase assay. Modulation of integrin receptor levels was determined by Western immunoblotting. Results: Tamoxifen exposure resulted in impaired cell cycle progression of human breast epithelial cells with a dose-dependent G2/M-phase arrest and reduced cell proliferation. Irrespective of tamoxifen treatment, the percent cellular adhesion to fibronectin and collagen type I by MCF-10A cells was significantly greater in high-density models compared to low-density models. Following tamoxifen treatment the adhesion was reduced in all density models. Consistent with the tamoxifen-induced lower adhesion, the integrin α1 and β3 levels were reduced in a dose-dependent way. Conclusion: These data support the hypothesis that tamoxifen affects the normal breast epithelium and its adhesion capacity, which may contribute to the clinically observed decrease in breast density and a potential reduced risk of breast tumor establishment. Citation Format: Rosendahl AH, Puig Blasco L, Borgquist S. Towards breast cancer prevention through reduced breast density: Suppressive effects of tamoxifen on normal breast epithelial cells [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P5-14-06.

Tamoxifen activates hypothalamic l-dopa synthesis to stimulate ovarian estrogen production in chicken

Estrogen is the primary sex hormone responsible for the development and modulation of the female reproductive system in all vertebrates including avian species. The actions of estrogen are mediated by the estrogen receptor, which could be modulated by the selective estrogen receptor modulator tamoxifen (TAM). In this study, we administered TAM into the actively laying chicken to investigate the ovarian and hypothalamic responses to the estrogen action blockage. The laying was disrupted and the development of the pre-ovulatory hierarchical follicles was arrested. However, the TAM treatment caused an increase of estrogen level in both serum and ovary. Among the main estrogen targeted tissues, the hypothalamus showed specific dopaminergic activation as indicated by gene expression analysis. In the ovary, l-dopa, the precursor of dopamine, could stimulate the estrogen synthesis in undifferentiated follicles but not in the differentiated pre-ovulatory follicles. Thus, we established a feedback loop links ovarian estrogen production with hypothalamic l-dopa synthesis and we propose that the dopamine is involved in estrogen action to regulate the ovarian follicle development and ovulation.

A Survey among Breast Cancer Specialists on the Low Uptake of Therapeutic Prevention with Tamoxifen or Raloxifene.

With this survey, we aimed to address the reasons why physicians are reluctant to prescribe breast cancer-preventive therapy with the selective estrogen receptor modulators (SERM) tamoxifen or raloxifene despite a strong evidence of efficacy. A self-administered 5-point Likert questionnaire was given during breast cancer meetings in Europe or sent via email to rank the importance of 10 predefined reasons for low uptake of SERMs for breast cancer therapeutic prevention. Analyses tested the associations between the stated reasons and physician characteristics such as gender, age, country of work, and specialty. Of 246 delivered questionnaires, 27 were incomplete and were excluded from analysis. Overall, there was a small variability in response scores, with a tendency for physicians to give moderate importance (score = 3) to all 10 statements. However, the top five reasons were: the expected greater preventive effectiveness of aromatase inhibitors (70.3% with score >3), difficulty applying current risk models in clinical practice (69.9%), the lack of clarity on the most appropriate physician for prevention advice (68.4%), the lack of reliable short-term biomarkers of effectiveness (67.5%), and the lack of commercial interest in therapeutic prevention (66.0%). The lack of reliable short-term biomarkers showed a tendency to discriminate between medical oncologists and other breast specialists (OR = 2.42; 95% CI, 0.93-6.25). This survey highlights the complexity of prescribing decisions among physicians in this context. Coupled with the known barriers among eligible women, these data may help to identify strategies to increase uptake of breast cancer therapeutic prevention. Cancer Prev Res; 11(1); 38-43. ©2017 AACR.

Mechanistic Insights From Global Metabolomics Studies into Synergistic Bactericidal Effect of a Polymyxin B Combination With Tamoxifen Against Cystic Fibrosis MDR Pseudomonas aeruginosa

Polymyxins are amongst the most important antibiotics in modern medicine, in recent times their clinical utility has been overshadowed by nosocomial outbreaks of polymyxin resistant MDR Gram-negative ‘superbugs’. An effective strategy to surmount polymyxin resistance is combination therapy with FDA-approved non-antibiotic drugs. Herein we used untargeted metabolomics to investigate the mechanism(s) of synergy between polymyxin B and the selective estrogen receptor modulator (SERM) tamoxifen against a polymyxin-resistant MDR cystic fibrosis (CF) Pseudomonas aeruginosa FADDI-PA006 isolate (polymyxin B MIC=8 mg/L , it is an MDR polymyxin resistant P. aeruginosa isolated from the lungs of a CF patient). The metabolome of FADDI-PA006 was profiled at 15 min, 1 and 4 h following treatment with polymyxin B (2 mg/L), tamoxifen (8 mg/L) either as monotherapy or in combination. At 15 min, the combination treatment induced a marked decrease in lipids, primarily fatty acid and glycerophospholipid metabolites that are involved in the biosynthesis of bacterial membranes. In line with the polymyxin-resistant status of this strain, at 1 h, both polymyxin B and tamoxifen monotherapies produced little effect on bacterial metabolism. In contrast to the combination which induced extensive reduction (≥ 1.0-log2-fold, p ≤ 0.05; FDR ≤ 0.05) in the levels of essential intermediates involved in cell envelope biosynthesis. Overall, these novel findings demonstrate that the primary mechanisms underlying the synergistic bactericidal effect of the combination against the polymyxin-resistant P. aeruginosa CF isolate FADDI-PA006 involves a disruption of the cell envelope biogenesis and an inhibition of aminoarabinose LPS modifications that confer polymyxin resistance.

Estrogen and soy isoflavonoids decrease sensitivity of medulloblastoma and central nervous system primitive neuroectodermal tumor cells to chemotherapeutic cytotoxicity

BackgroundOur previous studies demonstrated that growth and migration of medulloblastoma (MB), the most common malignant brain tumor in children, are stimulated by 17β-estradiol. The growth stimulating effects of estrogens are mediated through ERβ and insulin-like growth factor 1 signaling to inhibit caspase 3 activity and reduce tumor cell apoptosis. The objective of this study was to determine whether estrogens decreased sensitivity of MB cells to cytotoxic actions of chemotherapeutic drugs.MethodsUsing in vitro cell viability and clonogenic survival assays, concentration response analysis was used to determine whether the cytoprotective effects of estradiol protected human D283 Med MB cells from the cytotoxic actions of the MB chemotherapeutic drugs cisplatin, vincristine, or lomustine. Additional experiments were done to determine whether the ER antagonist fulvestrant or the selective ER modulator tamoxifen blocked the cytoprotective actions of estradiol. ER-selective agonists and antagonists were used to define receptor specificity, and the impacts of the soy-derived phytoestrogens genistein, daidzein, and s-equol on chemosensitivity were evaluated.ResultsIn D283 Med cells the presence of 10 nM estradiol increased the IC50 for cisplatin-induced inhibition of viability 2-fold from ~5 μM to >10 μM. In clonogenic survival assays estradiol decreased the chemosensitivity of D283 Med cells exposed to cisplatin, lomustine and vincristine. The ERβ selective agonist DPN and low physiological concentrations of the soy-derived phytoestrogens genistein, daidzein, and s-equol also decreased sensitivity of D283 Med cells to cisplatin. The protective effects of estradiol were blocked by the antiestrogens 4-hydroxytamoxifen, fulvestrant (ICI 182,780) and the ERβ selective antagonist PPHTP. Whereas estradiol also decreased chemosensitivity of PFSK-1 cells, estradiol increased sensitivity of Daoy cell to cisplatin, suggesting that ERβ mediated effects may vary in different MB celltypes.ConclusionsThese findings demonstrate that E2 and environmental estrogens decrease sensitivity of MB to cytotoxic chemotherapeutics, and that ERβ selective and non-selective inhibition of estrogen receptor activity blocks these cytoprotective actions. These findings support the therapeutic potential of antiestrogen adjuvant therapies for MB, and findings that soy phytoestrogens also decrease sensitivity of MB cells to cytotoxic chemotherapeutics suggest that decreased exposure to environmental estrogens may benefit MB patient responses to chemotherapy.

Oestrogen receptor expression in melanoma.

Sexual hormones share a common cholesterol-derived steroid backbone and comprise oestrogens, gestagens and androgens. They elicit numerous physiological and pathological functions; for example androgens are known to contribute to prostatic cancer development, whereas oestrogens are of major importance in the pathogenesis of breast cancer. In 1986, the presence of oestrogen receptors (ER) on breast cancer cells was described as one of the first biomarkers in oncology.1 ER expression is still routinely used both for predictive and therapeutic purposes with the selective ER modulator tamoxifen remaining an efficacious breast cancer treatment both in the adjuvant and palliative setting. The ‘classical’ ERs (ERα and ERβ) are found in many other tissues, such as lung, colorectal mucosa, thyroid tissue or lymphoid cells. Observations of darkening or sometimes growing melanocytic nevi in pregnancy as well as of prognostic differences between female and male melanoma patients suggested that sexual hormones may also impact on melanocyte function and melanoma development.2 Both ‘classical’ ERs have been detected in melanoma tissue, with ERβ being the predominant subtype 3 Already over 20 years ago, tamoxifen was tested in combination with chemotherapy in the treatment of metastatic melanoma and demonstrated improved response rates compared to chemotherapy alone.4 However, a meta-analysis of subsequent clinical trials with tamoxifen did not detect a positive influence of additional tamoxifen treatment on overall survival in advanced melanoma.5 The pathogenetic impact of ER expression differs between different cancer types. For example, ERβ proves to have an antiproliferative effect in prostate cancer, while, in contrast, its expression is associated with poor prognosis in ovarian cancer.6, 7 Besides ER α and β, also ‘nonclassical’ oestrogen receptors such as the G protein-coupled oestrogen receptor (GPER) are investigated with growing interest. In the present issue of this journal, Fabian et al.8 report on differential expression of GPER in a total of 81 primary melanomas, either pregnancy-associated melanoma (PAM) or nonpregnancy-associated melanoma (NPAM). GPER is thought to allow for alternative oestrogen-mediated signalling via the MAP-kinase and other intracellular pathways in cells lacking classical ERs. As for other ERs, its role in the pathogenesis of hormone-related cancer is ambiguous with both tumour-promoting and tumour-protective effects proposed in the literature.9 In melanoma, Fabian and colleagues found a significantly higher immunohistochemical and immunofluorescent cytoplasmatic expression of GPER in PAM compared with NPAM (78.4% vs. 27.9%; P = 0.0000), while similar frequencies of ER β expression were reported in both groups (81.6% vs. 60.5%). For immunohistochemical analyses, the authors used ER antibody clones that have recently been considered as specific.10 This is important, because a number of other available ER antibodies have been shown not to stain consistently or to have problems with cross-reactivity. Double receptor expression of ER β and GPER was detected in 73% and 28% of PAM and NPAM, respectively, and was associated with established positive prognostic markers such as lower Breslow thickness, lower mitotic rate and presence of peritumoural lymphocyte infiltration. Hence, the authors suggest that immunohistochemical double ER expression may serve as a novel prognostic indicator in melanoma. This hypothesis needs additional investigation. First, because double receptor expression was not associated with improved disease-free survival in multivariate analysis, which may be attributed to the small sample size of the study, but may also reflect that ERs are predominantly expressed on thinner, less proliferative primary melanomas for other, yet unknown reasons. Second, although ER expression was significantly more frequent in PAM, no survival difference was demonstrated for PAM compared to NPAM, which is in line with the literature on melanoma in pregnancy.11 In addition, the relevance of driver mutations such as BRAF or NRAS for ER expression is not understood. Taken together, the influence of oestrogen and associated receptor expression patterns on melanoma development remains unclear. Further research in this field is needed, especially as the superior prognosis of female melanoma patients continues to imply a role of sexual hormones in melanoma pathogenesis. Contrary parts of oestrogens (tumour-promoting) and progestins (protective) have been recently suggested in this context.12 Moreover, the role of antihormonal therapeutics such as tamoxifen may be worth rethinking in selected melanoma patients.13

Comprehensive genomic sequencing for triple negative breast cancer in Japan.

e23122 Background: Breast cancer is the leading cancer among women both in US and Japan. Triple negative breast cancer (TNBC) is the subset of breast cancers that are negative for estrogen receptor (ER), progesterone receptor, and HER2. While the selective ER modulator tamoxifen or anti-HER2 therapy for breast cancer patients with ER positive or HER2 protein overexpression are the most successful examples of targeted therapies, only limited therapies are available for patients with TNBCs, which are associated with a poor prognosis. Advance in next-generation sequencing enables us to identify actionable driver mutations that can be potentially treated by targeted therapies in each cancer patient. The aim of this study is to examine actionable driver mutations in TNBCs in Japan by comprehensive genomic sequencing (CGS) with 435 gene panel, and compare the driver events in Japan with TCGA database to validate the utility of CGS. Methods: We examined all exons of 435 known cancer genes in Japanese TNBC patients (N = 53) by CGS and evaluated for concordance among independent data obtained from The Cancer Genome Atlas-TNBC whole exome sequencing database (N = 123). Results: Oncogenic driver mutations were identified in 51 of 53 Japanese patients (96%) with TNBC and 36 of 53 patients (67%) harbored mutations in genes associated with FDA-approved targeted therapies, indicating the potential clinical utility of a large gene panel for evaluating patients with TNBC. Among 80 total genetic alterations, frequently mutated genes ( > 10% patients) were TP53, PIK3CA and PTEN. Overall, the mutation spectrum of the Japanese patients is similar to that of the TCGA population, except amplification of MYC. Conclusions: Use of a CGS panel of 435 genes can reliably identify all of the critical mutations in TNBC patients, which are similar as TCGA data. The information derived from CGS can be used to determine the optimal treatment for TNBC patients.

A shortened tamoxifen induction scheme to induce CreER recombinase without side effects on the male mouse skeleton

The selective estrogen receptor modulator tamoxifen exerts estrogen agonistic or antagonistic actions on several tissues, including bone. The off-target effects of tamoxifen are one of the most widely recognized pitfalls of tamoxifen-inducible Cre recombinases (CreERs), potentially confounding the phenotypic findings. Still, the validation of tamoxifen induction schemes that minimize the side effects of the drug has not been addressed. Here, we compared the side effects on the skeleton and other androgen-responsive targets of a shortened tamoxifen regimen (2 doses of 190 mg/kg body weight by oral gavage) to a standard protocol (4 doses) and determined their efficiency in inducing CreER-mediated gene deletion. In addition, both a vehicle- and a 10-dose group, which served as a positive control for tamoxifen side effects, were also included. For this purpose, we generated male mice with a floxed androgen receptor (AR) and a neuron-specifically expressed CreER. Treatment with two doses of tamoxifen was the only regimen that did not diminish androgenic bioactivity, as assessed by both seminal vesicles and levator ani/bulbocavernosus muscle weights and serum testosterone concentrations. Similarly, trabecular and cortical femoral bone structure were dramatically altered by both the standard and high-dose protocols but not by the shortened version. Serum osteocalcin and bone-gene expression analyses confirmed the absence of effects on bone by 2 doses of tamoxifen. This protocol decreased AR mRNA levels efficiently and specifically in the nervous system. Thus, we optimized a protocol for tamoxifen-induced CreER gene deletion in mice without off-target effects on bone and male reproductive organs.

Direct and Systemic Administration of a CNS-Permeant Tamoxifen Analog Reduces Amphetamine-Induced Dopamine Release and Reinforcing Effects.

Amphetamines (AMPHs) are globally abused. With no effective treatment for AMPH addiction to date, there is urgent need for the identification of druggable targets that mediate the reinforcing action of this stimulant class. AMPH-stimulated dopamine efflux is modulated by protein kinase C (PKC) activation. Inhibition of PKC reduces AMPH-stimulated dopamine efflux and locomotor activity. The only known CNS-permeant PKC inhibitor is the selective estrogen receptor modulator tamoxifen. In this study, we demonstrate that a tamoxifen analog, 6c, which more potently inhibits PKC than tamoxifen but lacks affinity for the estrogen receptor, reduces AMPH-stimulated increases in extracellular dopamine and reinforcement-related behavior. In rat striatal synaptosomes, 6c was almost fivefold more potent at inhibiting AMPH-stimulated dopamine efflux than [3H]dopamine uptake through the dopamine transporter (DAT). The compound did not compete with [3H]WIN 35,428 binding or affect surface DAT levels. Using microdialysis, direct accumbal administration of 1 μM 6c reduced dopamine overflow in freely moving rats. Using LC-MS, we demonstrate that 6c is CNS-permeant. Systemic treatment of rats with 6 mg/kg 6c either simultaneously or 18 h prior to systemic AMPH administration reduced both AMPH-stimulated dopamine overflow and AMPH-induced locomotor effects. Finally, 18 h pretreatment of rats with 6 mg/kg 6c s.c. reduces AMPH-self administration but not food self-administration. These results demonstrate the utility of tamoxifen analogs in reducing AMPH effects on dopamine and reinforcement-related behaviors and suggest a new avenue of development for therapeutics to reduce AMPH abuse.

Down-regulation of Forkhead box protein A1 (FOXA1) leads to cancer stem cell-like properties in tamoxifen-resistant breast cancer cells through induction of interleukin-6

The selective estrogen receptor (ER) modulator tamoxifen inhibits ER signaling in breast cancer cells, and it is used for the treatment of ER-positive breast cancer. However, this type of cancer often acquires resistance to tamoxifen, and a better understanding of the molecular mechanisms underlying tamoxifen resistance is required. In this study, we established tamoxifen-resistant (TAM-R) breast cancer cells by long-term tamoxifen treatment of ER-positive breast cancer MCF7 cells. In TAM-R cells, expression of not only ERα, a major form of ER in breast cancer, but also its transcriptional partner forkhead box protein A1 (FOXA1) was found to be reduced. In contrast, activation of the transcription factor nuclear factor-κB (NF-κB) and expression of its target IL6 were increased in these cells. Stable expression of FOXA1, but not ERα, reduced the expression of IL6 in the FOXA1- and ERα-negative breast cancer MDA-MB-231 cells and TAM-R cells, without affecting the activation of the NF-κB signaling pathways. Conversely, FOXA1 knockdown induced IL6 expression in MCF7 cells. Chromatin immunoprecipitation assays revealed that FOXA1 bound to the promoter region of IL6 and repressed recruitment of the NF-κB complex to this region. TAM-R cells were found to have high mammosphere-forming activity, characteristics of cancer stem cells, and this activity was suppressed by NF-κB and IL6 signaling inhibitors. Taken together, these results suggest that FOXA1 suppresses expression of IL6 through inhibition of NF-κB recruitment to the IL6 promoter in an ERα-independent manner and that reduction in FOXA1 expression induces IL6 expression and contributes to cancer stem cell-like properties in TAM-R cells.

Expression of Ezrin and Estrogen Receptors During Cervical Carcinogenesis

Development of cervical squamous carcinoma (CXCA) is accompanied by changes in estrogen receptors (ERs, ERα and ERβ) and ezrin expression; however, reports have been conflicting. Using histologically documented staging of cervical biopsies, we determined ezrin and ER relationships during CXCA development. Immunoreactive (ir) ezrin, ir-ERα, and ir-ERβ were studied in normal epithelium, carcinoma in situ/cervical intraepithelial neoplasia (CIN) 1 to 3, and local invasion or metastatic CXCA. Results were compared using H scoring. Cultures of Caski metastatic CXCA cells were treated with estradiol and/or tamoxifen and studied for ER-driven ir-ezrin and the morphologic response. Koilocytosis was present and indicated viral presence. The ezrin H score increased from CIN1 to CIN3, reaching significant differences from normal by CIN3 (P = .004) and 2× normal in metastatic CXCA. Estrogen receptor α and ERβ H scores fell, reaching significance by CIN3 (ERα, P = .0001; ERβ, P = .024). During estradiol treatment, ezrin in Caski cells increased and localized to the periphery, in ruffles and processes. The selective ER modulator tamoxifen blocked the estradiol-induced changes. During cervical carcinogenesis, the usual relationship between estrogen and ezrin induction is abridged. This is consistent with the effects of human papilloma virus viral proteins such as E6 and E7 that upregulate SIXI, a protein that induces ezrin. Cervical carcinogenesis is progressive but arrests at the preinvasive stage for varying lengths of time. These studies suggest that changes in ezrin may be associated with the development of the invasive phenotype and penetration of the basement membrane. They also raise the possibility that inhibiting ezrin expression could be a target for the prevention of invasive CXCA.

Utilization of gynecologic services in women with breast cancer receiving hormonal therapy

The selective estrogen receptor modulator tamoxifen is now widely used for the treatment and prevention of breast cancer. Tamoxifen use has been associated with a variety of gynecologic problems. Despite the frequency with which hormonal therapy is used for the treatment of breast cancer, limited population-level data are available to describe the occurrence of gynecologic conditions and the use of surveillance testing in women receiving tamoxifen and aromatase inhibitors. We performed a population-based analysis among women with breast cancer receiving hormonal therapy with tamoxifen, a drug commonly used in premenopausal and sometimes postmenopausal women, to determine the frequency of gynecologic abnormalities and use of diagnostic and surveillance testing. We compared these findings to women treated with aromatase inhibitors, agents commonly used in postmenopausal women. The MarketScan database was used to identify women diagnosed with breast cancer from 2009 through 2013 who underwent mastectomy or lumpectomy. Women receiving tamoxifen (age <50 vs ≥50 years) were compared to women ≥50 years of age treated with aromatase inhibitors. We examined the occurrence of gynecologic symptoms and diseases (vaginal bleeding, endometrial polyps, endometrial hyperplasia, and endometrial cancer) and gynecologic procedures and interventions (transvaginal ultrasound, endometrial biopsy, hysteroscopy/dilation and curettage, and hysterectomy). Time-dependent analyses were performed to examine symptoms and testing. A total of 75,170 women, including 15,735 (20.9%) age <50 years treated with tamoxifen, 13,827 (18.4%) age ≥50 years treated with tamoxifen, and 45,608 (60.7%) age ≥50 years treated with aromatase inhibitors were identified. The cumulative incidence of any gynecologic symptom or pathologic diagnosis during the study period was 20.2%, 12.3%, and 3.5%, respectively (P < .001), while the cumulative incidence of any gynecologic procedure or intervention during the study period was 34.2%, 20.9%, and 9.0%, respectively (P < .0001). Among women without symptoms or pathology, interventions were performed in 20.0%, 11.0%, and 6.8%, respectively (P < .0001). Compared to women taking aromatase inhibitors, gynecologic symptoms, procedures, and pathology are higher for both premenopausal and postmenopausal women with breast cancer on tamoxifen. Increased efforts to curb use of gynecologic interventions in asymptomatic women are needed.

Novel Selective Estrogen Receptor Downregulators (SERDs) Developed against Treatment-Resistant Breast Cancer.

Resistance to the selective estrogen receptor modulator tamoxifen and to aromatase inhibitors that lower circulating estradiol occurs in up to 50% of patients, generally leading to an endocrine-independent ER+ phenotype. Selective ER downregulators (SERDs) are able to ablate ER and thus, theoretically, to prevent survival of both endocrine-dependent and -independent ER+ tumors. The clinical SERD fulvestrant is hampered by intramuscular administration and undesirable pharmacokinetics. Novel SERDs were designed using the 6-OH-benzothiophene (BT) scaffold common to arzoxifene and raloxifene. Treatment-resistant (TR) ER+ cell lines (MCF-7:5C and MCF-7:TAM1) were used for optimization, followed by validation in the parent endocrine-dependent cell line (MCF-7:WS8), in 2D and 3D cultures, using ERα in-cell westerns, ERE-luciferase, and cell viability assays, with 2 (GDC-0810/ARN-810) used for comparison. Two BT SERDs with superior in vitro activity to 2 were studied for bioavailability and shown to cause regression of a TR, endocrine-independent ER+ xenograft superior to that with 2.

Bisphenol A Does Not Mimic Estrogen in the Promotion of the In Vitro Response of Murine Dendritic Cells to Toll-Like Receptor Ligands.

Sex hormones affect immune responses and might promote autoimmunity. Endocrine disrupting chemicals such as bisphenol A (BPA) may mimic their immune effects. Conventional dendritic cells (cDCs) are pivotal initiators of immune responses upon activation by danger signals coming from pathogens or distressed tissues through triggering of the Toll-like receptors (TLRs). We generated in vitro murine cDCs in the absence of estrogens and measured the effects of exogenously added estrogen or BPA on their differentiation and activation by the TLR ligands LPS and CpG. Estrogen enhanced the differentiation of GM-CSF-dependent cDCs from bone marrow precursors in vitro, and the selective estrogen receptor modulators (SERMs) tamoxifen and fulvestrant blocked these effects. Moreover, estrogen augmented the upregulation of costimulatory molecules and proinflammatory cytokines (IL-12p70 and TNFα) upon stimulation by TLR9 ligand CpG, while the response to LPS was less estrogen-dependent. These effects are partially explained by an estrogen-dependent regulation of TLR9 expression. BPA did not promote cDC differentiation nor activation upon TLR stimulation. Our results suggest that estrogen promotes immune responses by increasing DC activation, with a preferential effect on TLR9 over TLR4 stimulation, and highlight the influence of estrogens in DC cultures, while BPA does not mimic estrogen in the DC functions that we tested.

From Breast Cancer to Antimicrobial: Combating Extremely Resistant Gram-Negative "Superbugs" Using Novel Combinations of Polymyxin B with Selective Estrogen Receptor Modulators.

Novel therapeutic approaches are urgently needed to combat nosocomial infections caused by extremely drug-resistant (XDR) "superbugs." This study aimed to investigate the synergistic antibacterial activity of polymyxin B in combination with selective estrogen receptor modulators (SERMs) against problematic Gram-negative pathogens. In vitro synergistic antibacterial activity of polymyxin B and the SERMs tamoxifen, raloxifene, and toremifene was assessed using the microdilution checkerboard and static time-kill assays against a panel of Gram-negative isolates. Polymyxin B and the SERMs were ineffective when used as monotherapy against polymyxin-resistant minimum inhibitory concentration ([MIC] ≥8 mg/L) Pseudomonas aeruginosa, Klebsiella pneumoniae, and Acinetobacter baumannii. However, when used in combination, clinically relevant concentrations of polymyxin B and SERMs displayed synergistic killing against the polymyxin-resistant P. aeruginosa, K. pneumoniae, and A. baumannii isolates as demonstrated by a ≥2-3 log10 decrease in bacterial count (CFU/ml) after 24 hours. The combination of polymyxin B with toremifene demonstrated very potent antibacterial activity against P. aeruginosa biofilms in an artificial sputum media assay. Moreover, polymyxin B combined with toremifene synergistically induced cytosolic green fluorescence protein release, cytoplasmic membrane depolarization, permeabilizing activity in a nitrocefin assay, and an increase of cellular reactive oxygen species from P. aeruginosa cells. In addition, scanning and transmission electron micrographs showed that polymyxin B in combination with toremifene causes distinctive damage to the outer membrane of P. aeruginosa cells, compared with treatments with each compound per se. In conclusion, the combination of polymyxin B and SERMs illustrated a synergistic activity against XDR Gram-negative pathogens, including highly polymyxin-resistant P. aeruginosa isolates, and represents a novel combination therapy strategy for the treatment of infections because of problematic XDR Gram-negative pathogens.

Inhibitory effects of Chinese nutritional herbs in isogenic breast carcinoma cells with modulated estrogen receptor function.

In estrogen receptor (ER)+ MCF-7 cells, ER represents a ligand-activated transcription factor, and 17β-estradiol (E2) represents its physiological ligand. Maintenance of the human breast carcinoma-derived MCF-7 cells with 0.7% serum selected a proliferative sub-population of E2-responsive cells with transiently non-functional ER due to limited availability of E2. Culture of MCF-7 cells in the presence of either 0.7% serum, <1 nM E2 or 0.7% serum + 20 nM E2 selected isogenic cells with either non-functional ER (ER-NF) or functional ER (ER-F) phenotype. The two phenotypes responded to the growth-promoting effects of E2 and to the growth-inhibitory effects of the selective ER modulator tamoxifen, indicating retention of E2 responsiveness. Comparative dose-response experiments with Chinese nutritional herbs on ER-NF and ER-F cells identified the inhibitory concentration (IC)50 values for these herbs, while the IC50 ratios for the ER-NF:ER-F phenotypes facilitated their rank ordering in terms of efficacy. Out of the 11 efficacious herbs tested, five herbs exhibited ER-F > ER-NF inhibitory activity, four exhibited ER-F = ER-NF inhibitory activity and two exhibited ER-NF > ER-F inhibitory activity. Extracts from representative herbs, Lycium barbarum bark, Epimedium grandiflorum and Cornus officinalis, from each of the three groups inhibited anchorage-independent growth, induced G1 or G2/M arrest and/or apoptosis, and generated anti-proliferative E2 metabolites. The differential growth inhibition in ER-NF and ER-F phenotypes, together with the mechanistic efficacy of representative herbs, identified potential leads for their efficacy on ER+ and/or ER- breast cancer.

Design and synthesis of triarylacrylonitrile analogues of tamoxifen with improved binding selectivity to protein kinase C

The clinical selective estrogen receptor modulator tamoxifen is also a modest inhibitor of protein kinase C, a target implicated in several untreatable brain diseases such as amphetamine abuse. This inhibition and tamoxifen’s ability to cross the blood brain barrier make it an attractive scaffold to conduct further SAR studies toward uncovering effective therapies for such diseases. Utilizing the known compound 6a as a starting template and guided by computational tools to derive physicochemical properties known to be important for CNS permeable drugs, the design and synthesis of a small series of novel triarylacrylonitrile analogues have been carried out providing compounds with enhanced potency and selectivity for PKC over the estrogen receptor relative to tamoxifen. Shortened synthetic routes compared to classical procedures have been developed for analogues incorporating a β-phenyl ring, which involve installing dialkylaminoalkoxy side chains first off the α and/or α′ rings of a precursor benzophenone and then condensing the resultant ketones with phenylacetonitrile anion. A second novel, efficient and versatile route utilizing Suzuki chemistry has also been developed, which will allow for the introduction of a wide range of β-aryl or β-heteroaryl moieties and side-chain substituents onto the acrylonitrile core. For analogues possessing a single side chain off the α- or α′-ring, novel 2D NMR experiments have been carried out that allow for unambiguous assignment of E- and Z-stereochemistry. From the SAR analysis, one compound, 6c, shows markedly increased potency and selectivity for inhibiting PKC with an IC50 of 80nM for inhibition of PKC protein substrate and >10μM for binding to the estrogen receptor α (tamoxifen IC50=20μM and 222nM, respectively). The data on 6c provide support for further exploration of PKC as a druggable target for the treatment of amphetamine abuse.

Update on Breast Cancer Risk Reduction Therapy

In women at increased risk of breast cancer age ≥35 years, the selective estrogen receptor modulator (SERM) tamoxifen should be discussed as an option to reduce the risk of estrogen receptor (ER)-positive breast cancer. In postmenopausal women, raloxifene, anastrozole, and exemestane should also be discussed as options for breast cancer risk reduction. Risk reduction with SERMs continues for at least 10 years in both premenopausal and postmenopausal women. Tamoxifen is not recommended for women with a history of deep vein thrombosis, pulmonary embolus, stroke, transient ischemic attack, or during prolonged immobilization. Chemoprevention with a SERM may be particularly beneficial to women with atypical hyperplasia, a 5-year risk of more than 5 %, in women with increased mammographic density, or in women with lobular carcinoma in situ. Aromatase inhibitor therapy is of value in high-risk postmenopausal women. Toxicity with tamoxifen is minimal in premenopausal women and is less with either raloxifene or an aromatase inhibitor in postmenopausal women.

Sex Differences in Airway Remodeling in a Mouse Model of Chronic Obstructive Pulmonary Disease.

After adjustment for the amount of smoking, women have a 50% increased risk of chronic obstructive pulmonary disease (COPD) compared with men. The anatomic basis and/or mechanism(s) of these sex-related differences in COPD are unknown. To characterize the impact of female sex hormones on chronic cigarette smoke-induced airway remodeling and emphysema in a mouse model of COPD. Airway remodeling and emphysema were determined morphometrically in male, female, and ovariectomized mice exposed to 6 months of cigarette smoke. Antioxidant- and transforming growth factor (TGF)-β-related genes were profiled in airway tissues. The selective estrogen receptor modulator tamoxifen was also administered during smoke exposure in a short-term model. Airway wall thickness of male and female human smokers at risk of or with mild COPD was measured using optical coherence tomography. Small airway wall remodeling was increased in female but not male or ovariectomized mice and was associated with increased distal airway resistance, down-regulation of antioxidant genes, increased oxidative stress, and activation of TGF-β1. These effects were prevented by ovariectomy. Use of tamoxifen as a therapeutic intervention mitigated smoke-induced increase in oxidative stress in female mice. Compared with male human smokers, female human smokers had significantly thicker airway walls. The excess risk of small airway disease in female mice after chronic smoke exposure was associated with increased oxidative stress and TGF-β1 signaling and also was related to the effects of female sex hormones. Estrogen receptor antagonism might be of value in reducing oxidative stress in female smokers.

Prepubertal tamoxifen treatment affects development of heifer reproductive tissues and related signaling pathways

Prepubertal exposure of the developing ovaries and reproductive tract (RT) to estrogen or xenoestrogens can have acute and long-term consequences that compromise the reproductive performance of cattle. This research examined effects of the selective estrogen receptor modulator tamoxifen (TAM) on gene and protein abundance in prepubertal ovaries and RT, with a particular focus on signaling pathways that affect morphology. Tamoxifen was administered to Holstein heifer calves (n=8) daily (0.3mg/kg subcutaneously) from 28 to 120 d of age, when tissues were collected. Control calves (n=7) received an equal volume of excipient. Weight, gross measurements, and samples of reproductive tissues were collected, and protein and mRNA were extracted from snap-frozen samples of vagina, cervix, uterus, oviduct, ovary, and liver. Neither estradiol nor insulin-like growth factor I (IGFI) concentrations in the serum were affected by TAM treatment. Tamoxifen treatment reduced ovarian weight independently from effects on antral follicle populations, as there was no difference in visible antral follicle numbers on the day of collection. Estrogen receptor α (ESR1) and β (ESR2) mRNA, ESR1 protein, IGFI, progesterone receptor, total growth hormone receptor, WNT4, WNT5A, and WNT7A mRNA, in addition to mitogen-activated protein kinase (MAPK) and phosphorylated MAPK proteins were affected differently depending on the tissue examined. However, neither IGFI receptor mRNA nor protein abundance were affected by TAM treatment. Results indicate that reproductive development in prepubertal Holstein heifer calves is TAM-sensitive, and that bovine RT and ovarian development are supported, in part, by estrogen receptor-dependent mechanisms during the period studied here. Potential long-term consequences of such developmental disruption remain to be defined.