Estrogen Receptor Transcriptional Activity Research Articles

Abstract PO2-24-04: Exploring the role and therapeutic potential of Ubiquitin Specific Peptidase 11 (USP11) in estrogen receptor positive breast cancer

Abstract Dysregulated estrogen receptor (ER) function is a key feature of 70% of breast cancers. In this setting ER primarily functions as a growth-controlling transcription factor driving pro-tumorigenic properties, thus there is a need to identify novel modulators of ER transcriptional activity as alternative therapeutic options. Previously, we showed a significant association between high ubiquitin specific protease 11 (USP11) expression and poor survival in ER+ breast cancer patients, but not in ER- patients, indicating a role for USP11 in ER+ subtypes. However, the precise role of USP11 in controlling ER function remains undescribed. To interrogate USP11 function in ER+ breast cancer we generated a CRISPR USP11 knockout MCF7 breast cancer cell line. Our results showed for the first time that USP11 knockout significantly reduces proliferation, induces G2 cell cycle arrest and apoptosis, abrogates ERα transcriptional activity, significantly impairs cell migration and invasion, whilst also impairing MCF7 cancer stem-cell like properties and malignant transformation in vitro. In addition, we also observed significant dysregulation of epithelial-mesenchymal transition-related markers including E-cadherin, N-cadherin, Snail and Slug. Using RNA-seq of MCF7 cells +/- estradiol, +/- stable USP11 knockdown we identified dysregulated pathways in protein binding, cell adhesion molecule binding and cell cycle regulation following USP11 modulation. Of note, gene expression analysis indicated NCOA3 as the most differentially expressed coding gene. Further validation confirmed a significant reduction in NCOA3- encoded Steroid receptor coactivator- 3 (SRC-3) protein expression following USP11 modulation with immunocytochemical analysis also indicating co-localisation within the nucleus. Frequently upregulated in breast cancer and associated with poor outcome, SRC-3 promotes ER transcriptional activity and co-activates a wide range of additional pro-tumorigenic transcription factors. Thus, SRC-3 modulation offers an attractive therapeutic target in breast cancer. This finding may present a novel role for USP11 in controlling SRC-3 and therefore associated ER transcriptional activity. We then aimed to explore the therapeutic potential of USP11. Although rare in primary breast cancer, activating mutations in the ER ligand-binding domain have recently been linked to recurrent, anti-endocrine resistant disease and metastasis. As such cancers remain dependent on ER-signalling for proliferation, but are resistant to ER targeted therapies, we identified USP11 as a potential novel therapeutic target. Using CRISPR knock-in ER mutant MCF7 cell lines expressing the four most common ER activating mutations, we demonstrated that USP11 knockdown continues to significantly reduce proliferation and abrogates mutant ERα transcriptional activity. We then explored amphipathic cell penetrating peptide RALA encapsulation as a delivery method for siRNA targeting USP11. Optimisation of nanoparticle delivery in the Y537S ER-mutant MCF7 breast cancer cell line achieved significant knockdown of USP11 and ER- related target genes including TFF1, PgR, GREB1 and PKIB in 2D with minimal associated cellular toxicity. To overcome the siRNA-related issues of rapid clearance upon systemic delivery, we then explored the use of a freeze-dried collagen-based scaffold model as an in vitro 3D RALA-encapsulated siRNA delivery system. Here we observed successful delivery of nanoparticle to MCF7 breast cancer cells, with a significant reduction in USP11 mRNA expression. Bio-compatible scaffold- facilitated delivery may therefore offer a more feasible translation of this siRNA-based therapeutic. Overall, this study highlights a novel role for USP11 in various oncogenic pathways. USP11 may therefore offer a novel therapeutic target to be exploited for the management of ER-positive breast cancer, including ER mutant breast cancer. Citation Format: Rachel Moore, Anna Blümel, Elspeth Ward, Elizabeth Sainsbury, Emer Conroy, Fergal O’Brien, Caroline Curtin, Simak Ali, Helen McCarthy, William Gallagher, Darran O'Connor. Exploring the role and therapeutic potential of Ubiquitin Specific Peptidase 11 (USP11) in estrogen receptor positive breast cancer [abstract]. In: Proceedings of the 2023 San Antonio Breast Cancer Symposium; 2023 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2024;84(9 Suppl):Abstract nr PO2-24-04.

Phenomenon of suppression of estrogen signaling in breast cancer cells under ultraviolet irradiation: role of Snail proteins

Introduction. The study of the effect of irradiation or any other DNA-damaging agents on the sensitivity of tumors to conservative therapy, drug or hormonal, is among the most imporant tasks that determine the efficiency of combined therapy of cancer patients.Aim. To investigate the effect of irradiation on the activity of key signaling proteins and the level of hormone dependence of breast cancer cells.Materials and methods. The experiments were performed on in vitro cultured estrogen-dependent MCF-7 breast cancer cells. Ultraviolet (UV) irradiation in the range of 254 nm with the intensity of 25–50 J/m2 was used as an experimental model to study the response of tumor cells to DNA damage. Cell growth rate was determined using the MTT test, cell survival after irradiation was analyzed using the colony-forming test. Estrogen receptor transcriptional activity was determined by reporter assay; cellular protein expression was determined by immunoblotting.Results. Single UV irradiation of MCF-7 cells leads to a marked increase in the level of apoptotic markers: p53, cPARP, suppression of expression of growth signaling proteins: CDK4/6 and estrogen receptor α (ERα). The above changes are accompanied with an increase in phosphorylation of Akt protein kinase and a marked increase in the expression of Snail1, one of the key proteins of epithelial-mesenchymal transition. In UV-resistant MCF-7/UVR cell subline obtained under repeated irradiation cycles, the levels of apoptotic and growth signaling proteins (p53, cPARP, CDK4/6) return to control levels, except for the phosphorylated form of Akt and Snail1, whose content remains high. Transfection of Snail1-expressing plasmid into MCF-7 cells is accompanied by activation of apoptotic signaling, suppression of ERα activity, and development of partial hormone resistance; however, the sensitivity of cells to irradiation is practically unchanged. Transfection of microRNA-181a-2, one of the microRNAs associated with cell resistance, simultaneously activates Akt and Snail1 and leads to the development of cross-resistance of cells to irradiation and hormonal drugs.Conclusion. The obtained data allow us to consider irradiation-induced Snail1 activation as one of the factors involved in deregulation of estrogen signaling and formation of cell resistance to hormonal drugs, while simultaneous activation of Akt and Snail1 is accompanied by the development of cross-resistance to irradiation and hormonal drugs.

Mixture Effects of Bisphenol A and Its Structural Analogs on Estrogen Receptor Transcriptional Activation.

Bisphenol A (BPA) exposure has been widely linked to endocrine-disrupting effects. Recently, many substitutes for BPA have been developed as safe structural analogs. However, they have still been reported to have similar adverse effects. The current study evaluated the effects of bisphenol A and eight structural analogs on the transcription of estrogen receptor alpha (ERα). The effects of binary and ternary mixtures prepared from different combinations of BPA analogs were also evaluated for transcription activity. The measured data of the mixtures were compared to the predicted data obtained by the full logistic model, and the model deviation ratio (MDR) was calculated to determine whether the effects were synergistic, antagonistic, or additive. Overall, the results suggest that the effect of bisphenol compound are additive in binary and ternary mixtures.

Modulation of angiogenic switch in reprogramming browning and lipid metabolism in white adipocytes

Thermogenic activation via trans-and de novo browning of white adipocytes is a promising strategy to accelerate lipid metabolism for regulating obesity-related disorders. In this study, we investigated the intricate interplay between angiogenic regulation and browning in white adipocytes using the bioactive compound, resveratrol (Rsv). Rsv has previously been documented for its regulatory influence on the trans and de novo browning of white adipocytes. Our findings revealed that concurrent activation of angiogenesis is prerequisite for inducing browning within the microenvironment of white adipocytes when exposed to browning activators. Additionally, we observed a significant browning effect on white adipocytes when the local adipose tissue environment was prompted to undergo angiogenesis, notably facilitated by a proangiogenic molecule known as Vascular endothelial growth factor (VEGF). Intriguingly, this effect was reversed when angiogenesis was inhibited by treatment with the antiangiogenic agent thalidomide. Furthermore, the study revealed the role of VEGF in paracrine activation of white adipocytes resulting in the induction of browning in both 3T3-L1 cell lines and primary mouse white adipocytes. The cross-talk between angiogenesis and browning was found to be initiated via the transcriptional activation of Estrogen receptor α (ERα) triggering the VEGF/VEGFR2 signaling pathway leading to browning and a reconfiguration of lipid metabolism within adipocytes. In conclusion, this study sheds light on the intricate cross-talk between angiogenesis and browning of white adipocytes. Notably, the findings underscore the reciprocal relationship between these processes, wherein inhibition of one process exerts discernible effects on the other.

Emerging organophosphate ester resorcinol bis(diphenyl phosphate) exerts estrogenic effects via estrogen receptor pathways

Environmental occurrence and human exposure of emerging organophosphate esters (eOPEs) have increased significantly in recent years. Resorcinol bis(diphenyl) phosphate (RDP) is one of the major eOPEs detected in indoor dust, but the knowledge on its toxicities and health risks is rather limited. In this study, we investigated the in vitro estrogenic effects and underlying mechanism of RDP in comparison with a legacy OPE triphenyl phosphate (TPHP). Our results showed that RDP promoted MCF-7 cell proliferation with the lowest effect concentration of 2.5 μM, and the maximum enhancement of 1.6 folds is greater than that of TPHP (1.3 folds). The effect was inhibited completely by an estrogen receptor (ER) antagonist, suggesting that ER activation was responsible for the enhancement. In luciferase reporter gene assays both RDP and TPHP activated ER transcriptional activity at 2.5 μM, but RDP activity was higher than TPHP. Competitive fluorescence binding assays showed that RDP bound to ER with an IC10 of 0.26 μM, which is 20 folds lower than TPHP (5.6 μM). Molecular docking simulation revealed that both RDP and TPHP interacted with ER at the binding pocket of estradiol, although the hydrogen bonds were different. Taken together, RDP exerted stronger estrogenic effects than TPHP through ER-mediated pathways and may pose more health risks.

Comparative study on estrogen receptor alpha dimerization and transcriptional activity of parabens.

Parabens are used as preservatives in various household products, including oral products, cosmetics, and hair/body washes. In recent years, the widespread use of parabens has raised concerns due to the potential health risks associated with their estrogenic effects. In the present study, we evaluated and compared the estrogenic activity of parabens using two cell-based in vitro tests: (1) bioluminescence resonance energy transfer (BRET)-based estrogen receptor alpha (ERα) dimerization using HEK293 cells that were stably transfected with ERα-fused NanoLuc luciferase (Nluc) and HaloTag (HT) expression vector, and (2) stably transfected transcriptional activation (STTA) assays using ERα-HeLa9903 cells. The following parabens were tested using the BRET-based ERα dimerization assay and showed estrogenic activity (PC20 values): methyl paraben (MP, 5.98 × 10-5M), ethyl paraben (EP, 3.29 × 10-5M), propylparaben (PP, 3.09 × 10-5M), butyl paraben (BP, 2.58 × 10-5M), isopropyl paraben (IsoPP, 1.37 × 10-5M), and isobutyl paraben (IsoBP, 1.43 × 10-5M). Except MP, all other parabens tested using the STTA assay also showed estrogenic activity: EP, 7.57 × 10-6M; PP, 1.18 × 10-6M; BP, 3.02 × 10-7M; IsoPP, 3.58 × 10-7M; and IsoBP, 1.80 × 10-7M. Overall, EP, PP, BP, IsoPP, and IsoBP tested positive for estrogenic activity using both assays. These findings demonstrate that most parabens, albeit not all, induce ERα dimerization and possess estrogenic activity.

Abstract 3079: Characterization of ER-AF2 inhibitors in breast cancer

Abstract Up to 80% of breast cancers (BCa) rely on the estrogen receptor (ER) for their growth and progression. This dependence on ER has led to many hormonal therapies that target this receptor. However, almost 40% of these cancers will acquire resistance over the course of the treatment period. One potential cause of resistance is mutations in the estrogen binding site (EBS) of ER. As such, there is an increasing need for novel inhibitors that targets ER at a site separate from the EBS. Here, we propose targeting the activation-function (AF2) pocket of ER that is important for cofactor binding and transcription activation. Billions of compounds were screened through an in-silico deep docking method, and potential AF2 inhibitors were then validated in cell-based and biophysical assays. We tested the effect of potential AF2 inhibitors on ER transcriptional activity using luciferase reporter assay in ER-positive T47D-kbluc cells. We then evaluated the effect of molecules on cell viability of ER-positive T47D and ER-negative MDA-MB-231 cells using PrestoBlue assays in order to exclude off-target effects. From these cell-based assays, we identified several inhibitors that effectively reduced transcriptional activity and viability in ER-positive T47D cells at low micromolar concentrations. We conducted PGC-1α peptide displacement assay to confirm their AF2 binding and estradiol displacement assays to exclude any binding to the EBS. Proximity ligation assay (PLA) showed disruption of the interaction between ER and coactivator SRC-3 upon treatment with ER-AF2 inhibitors in T47D cells. Current work focuses on confirming the direct binding between the compounds and recombinant ER-ligand binding domain by various biophysical assays (MST, BLI, and ITC). Future work aims to solve the structure of ER-LBD in a complex with our lead compound by X-ray crystallography. We predict that the use of potent ER-AF2 inhibitors along with current treatments, will provide a novel tactic that can act as a complementary therapeutic to target treatment resistance in ER+ BCa. Citation Format: Jane Foo, Francesco Gentile, Joseph Lee, Helene Morin, Shabnam Massah, Maria Guo, Jason Smith, Fuqiang Ban, Artem Cherkasov, Nada Lallous. Characterization of ER-AF2 inhibitors in breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3079.

Using in vitro bioassays to guide the development of safer bio-based polymers for use in food packaging.

Petroleum-based polymers traditionally used for plastic packaging production have been shown to leach dangerous chemicals such as bisphenol-A (BPA). Bio-based polymers are potentially safer alternatives, and many can be sustainably sourced from waste streams in the food industry. This study assesses bio-based polymers undergoing food packaging development for migration of endocrine disrupting leachates at the level of estrogen, androgen and progestagen nuclear receptor transcriptional activity. Reporter gene assays were coupled with migration testing, performed using standardised test conditions for storage and temperature. Test samples include nine bio-based polymers and four inorganic waste additives mixed with a traditional petroleum-based polymer, polypropylene. Thermoplastic starch material, polybutylene succinate, polycaprolactone, polybutylene adipate terephthalate (PBAT), two polylactic acid (PLA)/PBAT blends, polyhydroxybutyrate (PHB) and eggshell/polypropylene (10:90) presented no significant reduction in metabolic activity or hormonal activity under any test condition. Polypropylene (PP) presented no hormonal activity. Metabolic activity was reduced in the estrogen responsive cell line after 10 days migration testing of eggshell/polypropylene (0.1:99.9) in MeOH at 40°C, and PP in MeOH and dH20. Estrogenic agonist activity was observed after 10 days in poultry litter ash/polypropylene (10:90) in MeOH at 20°C and 40°C, poultry feather based polymer in MeOH and dH2O at 40°C, and eggshell/polypropylene (40:60) and PLA in dH2O at 40°C. Activity was within a range of 0.26–0.50 ng 17β-estradiol equivalents per ml, equating to an estrogenic potency of 3–∼2800 times less than the estrogenic leachate BPA. Poultry litter ash/polypropylene (10:90) in MeOH for 10 days presented estrogenic activity at 20°C and 40°C within the above range and anti-androgenic activity at 40°C. Progestagenic activity was not observed for any of the compounds under any test condition. Interestingly, lower concentrations of eggshell or PP may eliminate eggshell estrogenicity and PP toxicity. Alternatively eggshell may bind and eliminate the toxic elements of PP. Similarly, PLA estrogenic activity was removed in both PLA/PBAT blends. This study demonstrates the benefits of bioassay guidance in the development of safer and sustainable packaging alternatives to petroleum-based plastics. Manipulating the types of additives and their formulations alongside toxicological testing may further improve safety aspects.

Phase 2, two-stage study of letrozole and abemaciclib in estrogen receptor (ER) positive recurrent or persistent endometrial cancer (072)

Phase 2, two-stage study of letrozole and abemaciclib in estrogen receptor (ER) positive recurrent or persistent endometrial cancer (072)

In vitro activity of a panel of per- and polyfluoroalkyl substances (PFAS), fatty acids, and pharmaceuticals in peroxisome proliferator-activated receptor (PPAR) alpha, PPAR gamma, and estrogen receptor assays

Data demonstrate numerous per- and polyfluoroalkyl substances (PFAS) activate peroxisome proliferator-activated receptor alpha (PPARα), however, additional work is needed to characterize PFAS activity on PPAR gamma (PPARγ) and other nuclear receptors. We utilized in vitro assays with either human or rat PPARα or PPARγ ligand binding domains to evaluate 16 PFAS (HFPO-DA, HFPO-DA-AS, NBP2, PFMOAA, PFHxA, PFOA, PFNA, PFDA, PFOS, PFBS, PFHxS, PFOSA, EtPFOSA, and 4:2, 6:2 and 8:2 FTOH), 3 endogenous fatty acids (oleic, linoleic, and octanoic), and 3 pharmaceuticals (WY14643, clofibrate, and the metabolite clofibric acid). We also tested chemicals for human estrogen receptor (hER) transcriptional activation. Nearly all compounds activated both PPARα and PPARγ in both human and rat ligand binding domain assays, except for the FTOH compounds and PFOSA. Receptor activation and relative potencies were evaluated based on effect concentration 20% (EC20), top percent of max fold induction (pmaxtop), and area under the curve (AUC). HFPO-DA and HFPO-DA-AS were the most potent (lowest EC20, highest pmaxtop and AUC) of all PFAS in rat and human PPARα assays, being slightly less potent than oleic and linoleic acid, while NBP2 was the most potent in rat and human PPARγ assays. Only PFHxS, 8:2 and 6:2 FTOH exhibited hER agonism >20% pmax. In vitro measures of human and rat PPARα and PPARγ activity did not correlate with oral doses or serum concentrations of PFAS that induced increases in male rat liver weight from the National Toxicology Program 28-d toxicity studies. Data indicate that both PPARα and PPARγ activation may be molecular initiating events that contribute to the in vivo effects observed for many PFAS.

Abstract 102: IGFBP6 modulates estrogen receptor alpha phosphorylation and transcriptional activity in breast cancer cells

Abstract Insulin-like growth factors (IGFs) are signaling proteins which bind to insulin-like growth factor 1 receptor (IGF-1R) and induce a signaling cascade to promote proliferation and survival in breast cancer cells. Insulin-Like Growth Factor Binding Protein 6 (IGFBP-6) induces apoptosis by inhibiting IGF-1R upon binding to both IGF-1 and IGF-2, however, the role of IGFBP-6 in breast cancer has not been adequately studied. While IGFBP-6 can bind to both IGF-1 and IGF-2, the binding affinity for IGF2 is 20-fold higher compared to IGF1. To determine if IGFBP-6 modulates breast cancer cells, MCF-7 and T-47D cells were stably transfected with an IGFBP-6 expression plasmid. IGFBP6 over-expression resulted in decreased proliferation rates in both cell lines when compared to empty vector controls. To identify a mechanism of decreased proliferation rates, the activation of the IGF-1R-dependent AKT and MAPK mediators was measured. Reduced phosphorylation of MAPK and AKT was observed in both cell lines over-expressing IGFBP-6 compared to empty vector controls. MAPK and AKT phosphorylate ERα at serine 118 and serine 167 respectively, therefore, ERα phosphorylation at these residues was determined in the presence of IGFBP6 expression. Reduction in phosphorylation was greater in MCF-7 cells than T-47D cells when IGFBP6 was constitutively expressed. To determine if reduced ERα phosphorylation altered expression of known targets of ERα-modulated expression, such as IGF-1R and Progesterone Receptor (PR) was measured. Unexpectedly, IGF-1R and PR protein and transcript levels were greater in IGFBP6 over-expressing cells. Studies have shown that differences in ERα phosphorylation change the recruitment of transcriptional modulators associated with ERα-mediated transcription. These results suggest that despite reducing IGF-1R-dependent cell signaling, compensatory mechanisms may be induced to enhance ERα-mediated expression. Citation Format: Francisco Javier Lariz, Kevin D. Houston. IGFBP6 modulates estrogen receptor alpha phosphorylation and transcriptional activity in breast cancer cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 102.

Epigenetic Regulation of Estrogen Receptor Genes' Expressions in Adipose Tissue in the Course of Obesity.

Estrogen affects adipose tissue function. Therefore, this study aimed at assessing changes in the transcriptional activity of estrogen receptor (ER) α and β genes (ESR1 and ESR2, respectively) in the adipose tissues of obese individuals before and after weight loss and verifying whether epigenetic mechanisms were involved in this phenomenon. ESR1 and ESR2 mRNA and miRNA levels were evaluated using real-time PCR in visceral (VAT) and subcutaneous adipose tissue (SAT) of 78 obese (BMI > 40 kg/m2) and 31 normal-weight (BMI = 20–24.9 kg/m2) individuals and in 19 SAT samples from post-bariatric patients. ESR1 and ESR2 methylation status was studied using the methylation-sensitive digestion/real-time PCR method. Obesity was associated with a decrease in mRNA levels of both ERs in SAT (p < 0.0001) and ESR2 in VAT (p = 0.0001), while weight loss increased ESR transcription (p < 0.0001). Methylation levels of ESR1 and ESR2 promoters were unaffected. However, ESR1 mRNA in the AT of obese subjects correlated negatively with the expression of hsa-miR-18a-5p (rs = −0.444), hsa-miR-18b-5p (rs = −0.329), hsa-miR-22-3p (rs = −0.413), hsa-miR-100-5p (rs = −0.371), and hsa-miR-143-5p (rs = −0.289), while the expression of ESR2 in VAT correlated negatively with hsa-miR-576-5p (rs = −0.353) and in SAT with hsa-miR-495-3p (rs = −0.308). In conclusion, obesity-associated downregulation of ER mRNA levels in adipose tissue may result from miRNA interference.

The Estrogen Receptor α Signaling Pathway Controls Alternative Splicing in the Absence of Ligands in Breast Cancer Cells.

Simple SummaryAberrant alternative splicing is now considered a hallmark of cancer, including breast cancer. This results in the production of novel tumor-specific splice RNA variants, and the activation of biological processes such as epithelial-to-mesenchymal transition, leading to more aggressive phenotypes. The purpose of this study was to explore the role of estrogen receptor α in regulating the expression of RNA-binding proteins in luminal breast cancer cells and to determine the effects of its downregulation at the isoform level by exploring changes in isoform usage and alternative splicing. The findings of this study unravel a novel layer of gene regulation mediated by estrogen receptor α, which is fundamental for breast cancer cell growth as well as epithelial-to-mesenchymal transition. Finally, we foresee that this novel feature should be considered when studying the functional roles of estrogen receptor α in the onset and progression of breast cancer.Background: The transcriptional activity of estrogen receptor α (ERα) in breast cancer (BC) is extensively characterized. Our group has previously shown that ERα controls the expression of a number of genes in its unliganded form (apoERα), among which a large group of RNA-binding proteins (RBPs) encode genes, suggesting its role in the control of co- and post-transcriptional events. Methods: apoERα-mediated RNA processing events were characterized by the analysis of transcript usage and alternative splicing changes in an RNA-sequencing dataset from MCF-7 cells after siRNA-induced ERα downregulation. Results: ApoERα depletion induced an expression change of 681 RBPs, including 84 splicing factors involved in translation, ribonucleoprotein complex assembly, and 3′end processing. ApoERα depletion results in 758 isoform switching events with effects on 3′end length and the splicing of alternative cassette exons. The functional enrichment of these events shows that post-transcriptional regulation is part of the mechanisms by which apoERα controls epithelial-to-mesenchymal transition and BC cell proliferation. In primary BCs, the inclusion levels of the experimentally identified alternatively spliced exons are associated with overall and disease-free survival. Conclusion: Our data supports the role of apoERα in maintaining the luminal phenotype of BC cells by extensively regulating gene expression at the alternative splicing level.

Evaluation of Estrogen Receptor Agonistic Activity of Medicinal Herbs Using Organization for Economic Cooperation and Development Transactivation Assay with Rat Liver S9 Fraction.

A number of studies employing different in vitro assays have demonstrated the estrogen-like activity of natural substances. All assays have their advantages and limitations as a screening tool. No single in vitro assay is considered ideal for predicting estrogenic action in a complex in vivo system. To assess agonistic activities of several medicinal herbs on the estrogen receptor (ER) and their metabolic alteration, the Organization for Economic Cooperation and Development (OECD) Performance-Based Test Guideline No. 455 in vitro assay was performed in this study using recombinant VM7Luc4E2 cells in combination with rat liver S9 fractions. Ethanol extracts of medicinal herbs showed binding affinities for ER-α and ER-β at different levels. However, luciferase reporter assay using VM7Luc4E2 cells revealed that only two test extracts [Pueraria lobata root extract (PLE); Glycyrrhiza glabra root extract (GGE)] exhibited ER transcriptional activity when their activities were compared with the response by 17β-estradiol. Importantly, incubation of PLE or GGE with rat liver S9 fractions increased their ER transcriptional activities, in particular when phase I metabolic enzymes were activated. Puerarin and glabridin were the most abundant isoflavones found in PLE and GGE, respectively. The present results demonstrate that PLE and GGE possess potential as ER agonists with their metabolic activation. This study also suggests that the application of OECD in vitro assay with rat liver S9 fraction is an efficient screening tool to evaluate estrogenic activities of natural substances.

Assessment of agonistic and antagonistic properties of humidifier disinfectants to the estrogenic and androgenic receptors by transactivation assay.

Before being recalled and banned from the Korean market, humidifier disinfectants (HDs) were added to the humidifier water tank to prevent microbial growth. The known HDs active ingredients included the are oligo(2-(2-ethoxy)ethoxyethyl guanidine (PGH), polyhexamethylene guanidine (PHMG), a mixture of methylisothiazolinone (MIT) and chloromethylisothiazolinone (CMIT), didecyldimethyl ammonium chloride (DDAC), Sodium dichloroisocyanurate (NaDCC), and alkyldimethylbenzyl ammonium chloride (BAC). Previous epidemiological studies have suggested that PHMG induces fatal lung disease in pregnant, post-partum women, and young children. In an animal study, a mixture of DDAC and BAC exhibited decreased fertility and fecundity; increased time to first litter, longer pregnancy intervals, fewer pups per litter, and fewer pregnancies. In this study, endocrine-disrupting effects of HDs were investigated using estrogen receptor (ER) and androgen receptor (AR) transactivation assay based on OECD Test guidelines. Unexpectedly, unlike the previously reported reproductive toxicity data, in the present study, HDs did not show ER and AR transcriptional activation agonist and/or antagonist effects. However, it is difficult to conclude that HDs has no endocrine disruption effects, and further research on the effects of HDs mixtures, and in vivo tests including Uterotrophic bioassay and Hershberger bioassay would be necessary.

USP35, regulated by estrogen and AKT, promotes breast tumorigenesis by stabilizing and enhancing transcriptional activity of estrogen receptor \u03b1

Although endocrine therapies targeting estrogen receptor α (ERα) are effective in managing ER positive (+) breast cancer, many patients have primary resistance or develop resistance to endocrine therapies. In addition, ER+ breast cancer with PIK3CA activating mutations and 11q13-14 amplification have poor survival with unclear mechanism. We uncovered that higher expression of deubiquitinase USP35, located in 11q14.1, was associated with ER+ breast cancer and poor survival. Estrogen enhanced USP35 protein levels by downregulating USP35-targeting miRNA-140-3p and miRNA-26a-5p. USP35 promoted the growth of ER+ breast cancer in vitro and in vivo, and reduced the sensitivity of ER+ breast cancer cells to endocrine therapies such as tamoxifen and fulvestrant. Mechanistically, USP35 enhanced ERα stability by interacting and deubiquitinating ERα, and transcriptional activity of ERα by interacting with ERα in DNA regions containing estrogen response element. In addition, AKT, a key effector of PI3K, phosphorylated USP35 at Serine613, which promoted USP35 nuclear translocation, ERα transcriptional activity, and the growth of ER+ breast cancer cells. Our data indicate that USP35 and ERα form a positive feedback loop in promoting the growth of ER+ breast cancer. USP35 may be a treatment target for ER+ breast cancer with endocrine resistance or with PIK3CA mutations or hyperactivation of the PI3K pathway.

Еstrogen receptor α (ESR1) and SRC family kinase (LYN) gene's mutations associated with ovarian cancer endocrine therapy resistance

Recently multiple data accumulated concerning mutations in the ESR1 gene coding estrogen receptor α (mutESR1) and in the LYN gene coding non receptor tyrosine kinase SRC family member (mutLYN) that are associated with endocrine therapy resistance and that could be considered as markers of endocrine therapy efficiency. In case of gynecologic cancers including ovarian cancer the most frequent mutESR1 are ESR1L536H/P/R/V , ESR1Y537S/N/C/H, ESR1D538G that emerge in the course of hormonotherapy especially using aromatase inhibitors. mutLYN including LYNE159K, LYND189Y, LYNK209N, LYNA370T, LYNG418R, LYNA503D are also identified. mutESR1 and mutLYN increase transcriptional activity of estrogen receptor α (ERα) coded with ESR1 gene and catalytic activity of LYN kinase inducing endocrine therapy resistance. Interdependence of ESR1 and LYN genes is revealed at the level of proteins that they code as the kinases of the SRC family including LYN activate ERα-dependent transcription due to the phosphorylation of ERα at Y537 amino-acid residue that is the most frequently mutated in tumors with endocrine therapy resistance. The aim of the review is revealing the clinical correlations of mutESR1 and mutLYN with the ovarian cancer endocrine therapy resistance that opens perspectives of mutESR1 and mutLYN use as new predictive markers of ovarian cancer and development of more efficient anti-tumor medicaments. In the review the information obtained from PubMed database for the last 20 years using the following key words: ESR1, LYN, mutation(s), estrogen receptor α (ERα), LYN kinase, SRC family kinases, ovarian cancer, gynecologic(al) cancer is discussed.

A genome-scale CRISPR Cas9 dropout screen identifies synthetically lethal targets in SRC-3 inhibited cancer cells

Steroid receptor coactivator 3 (SRC-3/NCoA3/AIB1), is a key regulator of gene transcription and it plays a central role in breast cancer (BC) tumorigenesis, making it a potential therapeutic target. Beyond its function as an important regulator of estrogen receptor transcriptional activity, SRC-3 also functions as a coactivator for a wide range of other transcription factors, suggesting SRC-3 inhibition can be beneficial in hormone-independent cancers as well. The recent discovery of a potent SRC-3 small molecule inhibitor, SI-2, enabled the further development of additional related compounds. SI-12 is an improved version of SI-2 that like SI-2 has anti-proliferative activity in various cancer types, including BC. Here, we sought to identify gene targets, that when inhibited in the presence of SI-12, would lead to enhanced BC cell cytotoxicity. We performed a genome-scale CRISPR-Cas9 screen in MCF-7 BC cells under conditions of pharmacological pressure with SI-12. A parallel screen was performed with an ER inhibitor, fulvestrant, to shed light on both common and distinct activities between SRC-3 and ERα inhibition. Bearing in mind the key role of SRC-3 in tumorigenesis of other types of cancer, we extended our study by validating potential hits identified from the MCF-7 screen in other cancer cell lines.

Abstract PS17-31: Investigating the estrogen receptor Y537S mutation in transgenic models of luminal B breast cancer

Abstract Breast cancer is the most prevalent cancer in women and over two-thirds of cases express the estrogen receptor (ER). Significantly, metastatic ER positive breast cancer is the leading cause of breast cancer mortality. Despite the success of endocrine therapy to treat ER-positive breast cancers, resistance to treatment is a major problem and relapse commonly occurs though patients initially respond well to treatment. The ER Y537S mutant represents one of the most common gain-of-function mutations detected in the metastatic biopsies of patients with ER-positive breast cancer. Previous in-vitro analyses have shown that the ER Y537S mutant exhibits enhanced ER transcriptional activity by adopting a ligand-independent agonist confirmation. In our study, we seek to provide a deeper understanding of the role of this mutant by modeling the human ER Y537S mutant (ER Y541S in mice). Our lab has generated a Cre-inducible knock-in mouse model expressing the activating point mutation driven by the endogenous ER promoter, and it has been shown that when expressed ubiquitously the mutated ER leads to dramatic developmental effects. In order to further our observations in the context of endocrine resistant metastatic breast cancer, we characterize mamary tumour growth of the ER Y541S mutant in combination with luminal B models of mammary tumourigenesis. Consistent with the notion that these ER mutations occur seldom in primary tumours, preliminary data shows that tumour onset and tumour outgrowth is unaffected by the activating point mutation. When analysing tumours from both ER mutant and wildtype ER control animals, it was found that tumours with mutant ER display more basal-like cytokeratins at the RNA level via RNA sequencing and at the protein level via immunohistochemistry. This expression pattern is often associated with poorer prognosis in the clinic. Through ongoing analyses, we also seek to better understand our model through tumour regression studies (doxycycline withdrawal), treatment with tamoxifen and blocking the main source of estrogens via ovariotomies. By studying the ER Y537S mutation in models of luminal B breast cancer, we hope to investigate the factors leading to tumour recurrence and provide a deeper understanding of potential escape pathways to therapy. Citation Format: Gabriella Johnson, Joshua Roccamo, Cynthia Lavoie, Dongmei Zuo, Virginie Sanguin-Gendreau, Adrian Lee, Zheqi Li, Steffi Oesterreich, William Muller. Investigating the estrogen receptor Y537S mutation in transgenic models of luminal B breast cancer [abstract]. In: Proceedings of the 2020 San Antonio Breast Cancer Virtual Symposium; 2020 Dec 8-11; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2021;81(4 Suppl):Abstract nr PS17-31.

Comparative analysis of the AIB1 interactome in breast cancer reveals MTA2 as a repressive partner which silences E-Cadherin to promote EMT and associates with a pro-metastatic phenotype

Steroid regulated cancer cells use nuclear receptors and associated regulatory proteins to orchestrate transcriptional networks to drive disease progression. In primary breast cancer, the coactivator AIB1 promotes estrogen receptor (ER) transcriptional activity to enhance cell proliferation. The function of the coactivator in ER+ metastasis however is not established. Here we describe AIB1 as a survival factor, regulator of pro-metastatic transcriptional pathways and a promising actionable target. Genomic alterations and functional expression of AIB1 associated with reduced disease-free survival in patients and enhanced metastatic capacity in novel CDX and PDX ex-vivo models of ER+ metastatic disease. Comparative analysis of the AIB1 interactome with complementary RNAseq characterized AIB1 as a transcriptional repressor. Specifically, we report that AIB1 interacts with MTA2 to form a repressive complex, inhibiting CDH1 (encoding E-cadherin) to promote EMT and drive progression. We further report that pharmacological and genetic inhibition of AIB1 demonstrates significant anti-proliferative activity in patient-derived models establishing AIB1 as a viable strategy to target endocrine resistant metastasis. This work defines a novel role for AIB1 in the regulation of EMT through transcriptional repression in advanced cancer cells with a considerable implication for prognosis and therapeutic interventions.