Downregulation Of ERα Research Articles

Patuletin Ameliorates Inflammation and Letrozole-Induced Polycystic Ovarian Syndrome in Rats.

Concerns about inflammation-related issues affecting female reproductive health are growing. Chronic low-grade inflammation in women with polycystic ovarian syndrome (PCOS) affects follicular growth, ovulation, and androgen production. The present investigation aimed to elucidate the efficacy of flavonoid patuletin in ameliorating the letrozole-induced PCOS and associated inflammation in rats. Female Wistar rats (32 days old) were divided into five groups (n = 12): Group I, control; Group II, vehicle control; Group III, letrozole oral (1 mg/kg) for 28 days; Group IV and Group V treatment groups, patuletin i.p. (25 mg/kg) and clomiphene citrate + metformin i.p. (50 mg/kg + 300 mg/kg), respectively. Leterozole-induced PCOS and ovarian inflammation were ameliorated by patuletin, as reflected in the improved histopathology, prevention of cyst formation, significant upregulation of growth factors such as growth differentiation factor 9 (GDF-9) and bone morphogenetic protein-15 (BMP-15) expression, and a decrease in the pro-inflammatory cytokines TNF-α, IL-6, and COX-2. Additionally, the plasma levels of reproductive hormones were restored. Upregulation of FSH-R, PR, and CYP19a1, along with downregulation of ERα, LHR, CYP17a1, CYP11a1 and HSDβ17a1, showed the regulation of gonadotropin receptors and steroid biosynthesis genes in ovarian tissues. Patuletin demonstrated a promising protective approach against the biological model of PCOS by increasing the inflammation in ovarian tissues with consequent regulation of growth factors, enzymes, and hormones, and might be used as adjuvant therapy in the treatment of problems related to female reproductive health.

The G Protein Estrogen Receptor (GPER) is involved in the resistance to the CDK4/6 inhibitor palbociclib in breast cancer

BackgroundThe cyclin D1-cyclin dependent kinases (CDK)4/6 inhibitor palbociclib in combination with endocrine therapy shows remarkable efficacy in the management of estrogen receptor (ER)-positive and HER2-negative advanced breast cancer (BC). Nevertheless, resistance to palbociclib frequently arises, highlighting the need to identify new targets toward more comprehensive therapeutic strategies in BC patients.MethodsBC cell lines resistant to palbociclib were generated and used as a model system. Gene silencing techniques and overexpression experiments, real-time PCR, immunoblotting and chromatin immunoprecipitation studies as well as cell viability, colony and 3D spheroid formation assays served to evaluate the involvement of the G protein-coupled estrogen receptor (GPER) in the resistance to palbociclib in BC cells. Molecular docking simulations were also performed to investigate the potential interaction of palbociclib with GPER. Furthermore, BC cells co-cultured with cancer-associated fibroblasts (CAFs) isolated from mammary carcinoma, were used to investigate whether GPER signaling may contribute to functional cell interactions within the tumor microenvironment toward palbociclib resistance. Finally, by bioinformatics analyses and k-means clustering on clinical and expression data of large cohorts of BC patients, the clinical significance of novel mediators of palbociclib resistance was explored.ResultsDissecting the molecular events that characterize ER-positive BC cells resistant to palbociclib, the down-regulation of ERα along with the up-regulation of GPER were found. To evaluate the molecular events involved in the up-regulation of GPER, we determined that the epidermal growth factor receptor (EGFR) interacts with the promoter region of GPER and stimulates its expression toward BC cells resistance to palbociclib treatment. Adding further cues to these data, we ascertained that palbociclib does induce pro-inflammatory transcriptional events via GPER signaling in CAFs. Of note, by performing co-culture assays we demonstrated that GPER contributes to the reduced sensitivity to palbociclib also facilitating the functional interaction between BC cells and main components of the tumor microenvironment named CAFs.ConclusionsOverall, our results provide novel insights on the molecular events through which GPER may contribute to palbociclib resistance in BC cells. Additional investigations are warranted in order to assess whether targeting the GPER-mediated interactions between BC cells and CAFs may be useful in more comprehensive therapeutic approaches of BC resistant to palbociclib.

Tafazzin mediates tamoxifen resistance by regulating cellular phospholipid composition in ER-positive breast cancer.

Tamoxifen is the frontline therapeutic agent for the estrogen receptor-positive (ER + ) subtype of breast cancer patients, which accounts for 70-80% of total breast cancer incidents. However, clinical resistance to tamoxifen has become increasingly common, highlighting the need to identify the underlying cellular mechanisms. In our study, we employed a genome-scale CRISPR-Cas9 loss-of-function screen and validation experiments to discover that Tafazzin (TAZ), a mitochondrial transacylase, is crucial for maintaining the cellular sensitivity of ER+ breast cancer cells to tamoxifen and other chemotherapies. Mechanistically, we found that cardiolipin, whose synthesis and maturation rely on TAZ, is required to maintain cellular sensitivity to tamoxifen. Loss of metabolic enzymatic activity of TAZ causes ERα downregulation and therapy resistance. Interestingly, we observed that TAZ deficiency also led to the upregulation of lysophosphatidylcholine (LPC), which in turn suppressed ERα expression and nuclear localization, thereby contributing to tamoxifen resistance. LPC is further metabolized to lysophosphatidic acid (LPA), a bioactive molecule that supports cell survival. Thus, our findings suggest that the depletion of TAZ promotes tamoxifen resistance through an LPC-LPA phospholipid synthesis axis, and targeting this lipid metabolic pathway could restore cell susceptibility to tamoxifen treatment.

SAT428 The Effects Of Diphenyl Phthalate (DP) On Estrogen Receptor Alpha (ERα;) And Tumor Suppressor Gene (BRCA-1) In Breast Cancer Cells

Abstract Disclosure: K. Whittaker: None. E. Hallman: None. A. Zanib: None. S. Pfiffner: None. R. Yaldo: None. S. Dinda: None. Phthalates are a group of compounds that have been linked to xenoestrogenic activity which can lead to the proliferation of breast cancer cells. Specifically, Diphenyl Phthalate (DP) is a compound found in cosmetics, toys, plastic containers, and medical equipment. Previous studies have linked phthalates as endocrine-disrupting compounds (EDC) which may have an effect on diseases such as breast cancer. Due to the endocrine-disrupting actions of phthalates, it is critical to further investigate DP’s potential impact on breast cancer cells. This study investigates the estrogen-like effects of DP, both alone and in combination with hormones and antihormones on T-47D and MCF-7 breast cancer cell lines. The breast cancer cells were cultured in a medium that contained 5% charcoal-stripped fetal bovine serum (FBS) to ensure depletion of any endogenous steroids or growth factors. The cells were treated with varying concentrations of DP (25-250uM) for 24 hours. Through western blot analysis, alterations in the expression of ERα; related to the varying concentrations of DP were observed. A concentration-dependent decrease of ERα; expression levels was observed in both cell lines when compared to the control. A concentration-dependent increase of BRCA1 was seen in both cells. The optimal concentration of DP was revealed to be 200uM in T-47D breast cancer cells as it exhibited the most estrogen-like effect. The optimal concentration (200uM) was then used alone and in combination with hormones and antihormones for further investigation of DP on T47-D cells. Treatment with DP, E2 and the combination of DP and E2 for 24 hours showed a significant down-regulation of ERα in T-47D cells when compared to the control. These effects were sensitive to the presence of ICI showing significant down-regulation of ERα (approximately 80%) in T-47D cells. Image cytometric analysis with propidium iodide staining was utilized to examine the effects of DP on cellular viability in T-47D cells. Cells were treated for 6 days with DP concentrations ranging from 25-250 µM, and all concentrations displayed an increase in cell proliferation compared to the control in T47D cells. DP alone and in combination with E2 showed an increase in cell proliferation that was reversed when treated in combination with anti-hormones. RT-qPCR studies in T-47D cells revealed a transcriptional expression of ESR1 and BRCA-1 mRNA levels that correlate with the translational data from western blot analyses. Confocal microscopy, cell viability, and RT-qPCR analyses are in progress as well as evaluation on the effects of DP with hormones and antihormones on MCF-7 cells. Our studies offer an intriguing direction to explore the molecular mechanisms of DP as an EDC on the steroid receptors and tumor suppressor gene in breast cancer cells. Presentation: Saturday, June 17, 2023

Novel Correlation between TGF-β1/-β3 and Hormone Receptors in the Human Corneal Stroma.

This study investigated the interplay between transforming growth factor beta (TGF-β1/T1 and TGF-β3/T3), and sex hormone receptors using our 3D in vitro cornea stroma model. Primary human corneal fibroblasts (HCFs) from healthy donors were plated in transwells at 106 cells/well and cultured for four weeks. HCFs were supplemented with stable vitamin C (VitC) and stimulated with T1 or T3. 3D construct proteins were analyzed for the androgen receptor (AR), progesterone receptor (PR), estrogen receptor alpha (ERα) and beta (ERβ), luteinizing hormone receptor (LHR), follicle-stimulating hormone receptor (FSHR), gonadotropin-releasing hormone receptor (GnRHR), KiSS1-derived peptide receptor (KiSS1R/GPR54), and follicle-stimulating hormone subunit beta (FSH-B). In female constructs, T1 significantly upregulated AR, PR, ERα, FSHR, GnRHR, and KiSS1R. In male constructs, T1 significantly downregulated FSHR and FSH-B and significantly upregulated ERα, ERβ, and GnRHR. T3 caused significant upregulation in expressions PR, ERα, ERβ, LHR, FSHR, and GNRHR in female constructs, and significant downregulation of AR, ERα, and FSHR in male constructs. Semi-quantitative Western blot findings present the interplay between sex hormone receptors and TGF-β isoforms in the corneal stroma, which is influenced by sex as a biological variable (SABV). Additional studies are warranted to fully delineate their interactions and signaling mechanisms.

Abstract 474: Preclinical development of an oral selective estrogen receptor degrader (SERD) TFX06 for the treatment of ER+HER2− breast cancer

Abstract Breast cancer (BC) has recently surpassed lung cancer to become the most commonly diagnosed cancer in women worldwide. Approximately 70% of BC was ER+, in which estrogen receptor α (ERα, encoded by ESR1 gene) drives dysregulated cell proliferation. In clinic, ER+ BC has been effectively treated by endocrine therapy targeting estrogen or ER. As the first approved ERα degrader, fulvestrant has proven to be effective for locally advanced or metastatic BC. However, its clinical utilization is hampered by inconvenience of intramuscular injection, as well as its poor PK/PD profile and limited efficacy, especially in the patient population that developed ESR1 mutation-conferring drug resistance after the earlier line of treatment with an aromatase inhibitor. Thus, developing an oral and more effective therapy for ER+ BC remains an unmet medical need. We report herein discovery and preclinical investigation of a novel orally bioavailable SERD TFX06. TFX06 demonstrated potent binding affinity to ERα with a Ki of 0.10 nM and preferably antagonized ERα to ERβ with an IC50 value of 0.086 nM and 2.83 nM, respectively. TFX06 potently induced ERα degradation in ER+ BC cells and substantially inhibited cell proliferation in BC cell lines with ER wild type (WT), and MCF-7 cells expressing Y537S or D538G mutants. Oral administration of TFX06 demonstrated impressive antitumor efficacy in ER WT (TGI = 101%) and ER D538G-expressing (TGI = 99%) MCF-7 cell line-derived xenograft (CDX) models in mice. Similarly, in an ER+ BC patient-derived xenograft (PDX) model (HCI-013) with ER Y537S mutation, TFX06 also exerted excellent antitumor activity (TGI = 99%). Furthermore, TFX06 in combination with palbociclib achieved synergistic activity in MCF-7 CDX model. Moreover, TFX06 exhibited an excellent correlation between systemic/local drug exposure, pharmacodynamic modulation (i.e., ERα downregulation) and antitumor activity. Collectively, these findings demonstrate that TFX06 is a novel, orally bioavailable SERD. TFX06 demonstrates substantial antitumor activity in both in vitro and in vivo preclinical tumor models, including those expressing ESR1 mutations, through downregulation of ERα. The preclinical data warranted the clinical evaluation of TFX06 in human with an IND application submitted to the China NPMA. Citation Format: Jinping Wu, Ke An, Douglas D. Fang, Jianyu Lu, Lihong Hu, Jing Wang, Kaili Zhang, Yuanfeng Xia, Charles Ding, Shuhui Chen, Sha Wei. Preclinical development of an oral selective estrogen receptor degrader (SERD) TFX06 for the treatment of ER+HER2− 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 474.

Epigenetics in Canine Mammary Tumors: Upregulation of miR-18a and miR-18b Oncogenes Is Associated with Decreased ERS1 Target mRNA Expression and ERα Immunoexpression in Highly Proliferating Carcinomas

The expression of miRNAs is one of the main epigenetic mechanisms responsible for the regulation of gene expression in mammals, and in cancer, miRNAs participate by regulating the expression of protein-coding cancer-associated genes. In canine mammary tumors (CMTs), the ESR1 gene encodes for ERα, and represents a major target gene for miR-18a and miR-18b, previously found to be overexpressed in mammary carcinomas. A loss in ERα expression in CMTs is commonly associated with poor prognosis, and it is noteworthy that the downregulation of the ESR1 would appear to be more epigenetic than genetic in nature. In this study, the expression of ESR1 mRNA in formalin-fixed, paraffin-embedded (FFPE) canine mammary tumors (CMTs) was evaluated and compared with the expression levels of miR18a and miR18b, both assessed via RT-qPCR. Furthermore, the possible correlation between the miRNA expression data and the immunohistochemical prognostic factors (ERα immunoexpression; Ki67 proliferative index) was explored. A total of twenty-six FFPE mammary samples were used, including 22 CMTs (7 benign; 15 malignant) and four control samples (three normal mammary glands and one case of lobular hyperplasia). The obtained results demonstrate that miR-18a and miR-18b are upregulated in malignant CMTs, negatively correlating with the expression of target ESR1 mRNA. Of note, the upregulation of miRNAs strictly reflects the progressive loss of ERα immunoexpression and increased tumor cell proliferation as measured using the Ki67 index. The results suggest a central role of miR-18a and miR-18b in the pathophysiology of canine mammary tumors as potential epigenetic mechanisms involved in ERα downregulation. Moreover, as miRNA expression reflects ERα protein status and a high proliferative index, miR-18a and miR-18b may represent promising biomarkers with prognostic value. More detailed investigations on a larger number of cases are needed to better understand the influence of these miRNAs in canine mammary tumors.

P38 and ERK1/2-Dependent Activation of c-Jun Is Required for the Downregulation of Oxidative Stress-Induced ERα in Hypothalamic Astrocytes

Introduction: Gonadotropin-releasing hormone (GnRH) is a hypothalamic neuropeptide that plays important roles in the female fertility. Accumulating evidence suggests that ERα present in the astrocytes of the hypothalamus region is essential for production of GnRH. The astrocytes display age-related senescence associated to oxidative stress induced by the estrogen metabolites. However, it is still unclear whether and how ERα expression changes during astrocyte aging. Methods: Immunofluorescence was performed to analyze the ERα gene levels in hypothalamic astrocytes of naturally aging C57BL/6J female mice. We employed an oxidative stress cell model receiving 2-hydroxyestradiol (2OH-E2) intervention to confirm the downregulation of ERα expression in primary astrocytes. Western blot analysis was used to explore which oxidative stress signaling pathways induced loss of the ERα gene. Finally, ChIP-qPCR was employed to evaluate whether the c-Jun protein is able to regulate ERα gene expression. Results: Compared to young mice, we found that the ERα expression of mid-aged mice was significantly decreased. In hypothalamic astrocytes, 2OH-E2 treatment significantly reduced the expression of the ERα gene. Moreover, we observed that transcription factor c-Jun could directly inhibit transcriptional ERα gene expression and might also reduce it by decreasing H3K27 acetylation at promoter regions. Administration of the antioxidants Rg1 and astaxanthin significantly attenuated the decrease in ERα gene expression induced by oxidative stress. Conclusions: The current data demonstrate that oxidative stress leads to loss of ERα involving the activation of the p38 and ERK1/2 pathways and the induction of the c-Jun protein in hypothalamic astrocytes. C-Jun protein regulates ERα gene expression via direct transcriptional repression or involving histone acetylation modifications at ERα gene promoter sites.

PMON13 The Effects of Perfluorooctanesulfonic Acid (PFOS) on the Expression of Estrogen Receptor Alpha (ERα) and Tumor Suppressor Gene BRCA1 in Breast Cancer Cells

Abstract Perfluoroctanesulfonic Acid (PFOS) is a perfluorinated chemical (PFC) and endocrine-disrupting compound (EDC) found in fire-extinguishing foams, food packing, and commonly used household products such as nonstick cookware and cleaning products. PFOS is also an environmental toxicant that has polluted air, soil, and water in past years. Few studies have suggested PFOS may cause endocrine-disrupting effects, therefore it is critical to explore the effects of PFOS on breast cancer cells. This study examined the estrogenic-like effects of PFOS, alone and in combination with hormones and antihormones, on the expression of ERα and BRCA1 in T-47D and MCF-7 breast cancer cell lines by utilizing western blot analyses, cellular viability assays, confocal microscopy, apoptosis assay and RT-qPCR analyses. The cells were cultured with 5% charcoal-stripped fetal bovine serum (FBS) for six days to deplete endogenous steroids or growth factors. In the concentration-dependency study, cells were treated with various concentrations of PFOS (300µM-800µM) for 24 hours. Western blot analysis revealed alterations in the expression of ERα and BRCA1 related with these varying concentrations of PFOS (300 µM-800µM). In comparison to the control, a concentration-dependent decrease of ERα expression levels were seen in both cell lines. A concentration-dependent increase of BRCA1 was seen in both cells. Western blot analysis revealed the optimal concentration of PFOS to be 700 µM in cells, which exhibited the maximal estrogenic-like effect. To further examine the effects of PFOS on breast cancer cells, the optimal concentration (700 µM PFOS) was then used alone and in combination with hormones and anti-hormones in T-47D cells. Treatment with PFOS, E2and the combination of PFOS and E2 for 24 hours showed a significant down-regulation of ERα in T-47D cells when compared to the control. Treatment of PFOS with antiestrogen ICI revealed a significant down-regulation of ERα (approximately 50%) in T-47D cells. Image cytometric analysis with propidium iodide staining was utilized to examine the effects of PFOS on cellular viability in T-47D cells. PFOS alone and in combination with E2 revealed an increase in cellular proliferation compared to the control in T-47D cells and these effects were sensitive to the presence of antiestrogens. RT-qPCR studies revealed a transcriptional expression of ESR1 and BRCA-1 mRNA levels that correlate with the translational data obtained via western blot analyses. Cytolocalization experiments and effects of PFOS with hormones and antihormones on MCF-7 cells studies are in progress. Our studies provide exciting leads to clearly delineate the molecular mechanisms of PFOS as an EDC on the steroid receptors and tumor suppressor gene in breast cancer cells. Presentation: Monday, June 13, 2022 12:30 p.m. - 2:30 p.m.

Hypoxia and ERα Transcriptional Crosstalk Is Associated with Endocrine Resistance in Breast Cancer.

Simple SummaryHormone receptor positive breast cancer patients are treated with anti-hormone molecules as a standard of care. However, resistance frequently occurs, leading to hormone resistant metastatic relapses in foreign organs. Understanding the molecular mechanisms through which breast cancer cells evade therapeutic pressure is of paramount interest. Hypoxia, which refers to oxygen deprivation and is characterized by the activation of hypoxia inducible factors, is a common feature of the solid tumor microenvironment, yet its influence on estrogen receptor alpha activity remains elusive. Here, we investigate the consequence of hypoxia and the signaling of hypoxia inducible factors on hormone responsiveness in breast cancer cells and its clinical implications.Estrogen receptor-alpha (ERα) is the driving transcription factor in 70% of breast cancers and its activity is associated with hormone dependent tumor cell proliferation and survival. Given the recurrence of hormone resistant relapses, understanding the etiological factors fueling resistance is of major clinical interest. Hypoxia, a frequent feature of the solid tumor microenvironment, has been described to promote endocrine resistance by triggering ERα down-regulation in both in vitro and in vivo models. Yet, the consequences of hypoxia on ERα genomic activity remain largely elusive. In the present study, transcriptomic analysis shows that hypoxia regulates a fraction of ERα target genes, underlying an important regulatory overlap between hypoxic and estrogenic signaling. This gene expression reprogramming is associated with a massive reorganization of ERα cistrome, highlighted by a massive loss of ERα binding sites. Profiling of enhancer acetylation revealed a hormone independent enhancer activation at the vicinity of genes harboring hypoxia inducible factor (HIFα) binding sites, the major transcription factors governing hypoxic adaptation. This activation counterbalances the loss of ERα and sustains hormone-independent gene expression. We describe hypoxia in luminal ERα (+) breast cancer as a key factor interfering with endocrine therapies, associated with poor clinical prognosis in breast cancer patients.

The combination of Elephantopus scaber and Phaleria macrocarpa leaves extract promotes anticancer activity via downregulation of ER-α, Nrf2 and PI3K/AKT/mTOR pathway

BackgroundElephantopus scaber and Phaleria macrocarpa have recently been interested as novel anticancer agents. However, there was no scientific evaluation of the anticancer effect of both plant combinations. ObjectiveThis study investigated the potential anticancer effects of combined E. scaber and P. macrocarpa leaves extract on human breast cancer cells lines. Materials and methodsT47D cells were treated with the combination of E. scaber and each part of P. macrocarpa (leaves/EL, mesocarp/EM, seed/ES and pericarp/EP). T47D cells were then exposed to three ratios (1:1, 2:1, and 1:2) of the best combination for 24, 48, and 72 h. The cell viability of T47D and TIG-1 cells was assessed using WST-1 assay. The apoptotic hallmarks were determined using FITC Annexin V-PI staining and DNA fragmentation assay. The cell proliferation and cell cycle profiles were analyzed using CFSE (carboxyfluorescein succinimidyl ester) and Propidium iodide-flowcytometry assays. The relative number of p-ERα, p-Nrf2, p-PI3K, p-AKT, and p-mTOR were assessed using flow cytometry. The molecular docking analysis was also performed to confirm the mechanism of the extract in silico. ResultsThe combination of E. scaber and P. macrocarpa leaves (EL) possessed strong cytotoxic activity (p < 0.05) than other combination groups and cisplatin. EL showed selective killing only to T47D cells. EL at a ratio of 2:1 potentially suppressed the cell viability and cell division, induced apoptosis, and arrested the cell cycle of T47D cells by triple inhibiting the p-Nrf2, p-ERα, and p-PI3K/AKT/mTOR signaling pathway. Molecular docking analysis confirmed that the possible mechanism of EL to reduce T47D cell growth was by inhibiting ERα and Nrf2-complex, resulting in the reduction in the crosstalk effect of Nrf2, ERα and PI3K/AKT/mTOR pathways. ConclusionThe combination of leaf extracts from E. scaber and P. macrocarpa caused cell death in breast cancer cells T47D and not in normal cells TIG-1; hence has the potential to show anticancer efficacy in preclinical and clinical trials.

2.45 GHz microwave radiation induced oxidative stress: Role of inflammatory cytokines in regulating male fertility through estrogen receptor alpha in Gallus gallus domesticus

Due to the growing number of gadgets emitting electromagnetic radiation (EMR), particularly microwave (MW) radiation, in our daily lives, it is believed that EMR have both long-term and short-term biological impacts that are quite concerning for avian as well as human health. Due to the negative impact of MW emitting equipment on the biological system this study looks into the mechanistic approach by which low-level of 2.45 GHz MW radiation causes an oxidative stress and inflammatory response in the testes micro-environment which further gets regulated by estrogen receptor alpha (ERα) expression in immature Gallus gallus domesticus leading to male infertility. Two weeks old immature male chickens were exposed to non-thermal low-level 2.45-GHz MW radiation for 2 h/day for 30 days (power density = 0.1264 mw/cm2 and SAR = 0.9978 W/kg). In the exposed group, morphometric examination of the testes revealed decreased testicular weight, volume and gonado-somatic index. Further, histological staining demonstrated a substantial reduction in the diameter of seminiferous tubules in the exposed group as compared to the control. The degree of oxidative stress was also determined showing an increase in oxidative stress parameters after exposure. The radiation exposed testes showed a significant increase in IL-1β immunoreactivity and decline in IL-10 immunoreactivity, indicating a sense of MW radiation-induced oxidative stress-regulated inflammatory response. A substantial reduction in ERα expression was also observed in exposed testes by Western blotting. Our investigations conclude that testes being vulnerable to free radical damage become an easy target organ for MW exposure induced oxidative and inflammatory stress. Therefore it becomes evident that it may cause male infertility in chicks via downregulation of ER-α in testis.

High Levels of Progesterone Receptor B in MCF-7 Cells Enable Radical Anti-Tumoral and Anti-Estrogenic Effect of Progestin.

The widely reported conflicting effects of progestin on breast cancer suggest that the progesterone receptor (PR) has dual functions depending on the cellular context. Cell models that enable PR to fully express anti-tumoral properties are valuable for the understanding of molecular determinant(s) of the anti-tumoral property. This study evaluated whether the expression of high levels of PR in MCF-7 cells enabled a strong anti-tumoral response to progestin. MCF-7 cells were engineered to overexpress PRB by stable transfection. A single dose of Promegestone (R5020) induced an irreversible cell growth arrest and senescence-associated secretory phenotype in MCF-7 cells with PRB overexpression (MCF-7PRB cells) but had no effect on MCF-7 cells with PRA overexpression. The growth-arresting effect was associated with downregulations of cyclin A2 and B1, CDK2, and CDK4 despite an initial upregulation of cyclin A2 and B1. R5020 also induced an evident activation of Nuclear Factor κB (NF-κB) and upregulation of interleukins IL-1α, IL-1β, and IL-8. Although R5020 caused a significant increase of CD24+CD44+ cell population, R5020-treated MCF-7PRB cells were unable to form tumorspheres and underwent massive apoptosis, which is paradoxically associated with marked downregulations of the pro-apoptotic proteins BID, BAX, PARP, and Caspases 7 and 8, as well as diminution of anti-apoptotic protein BCL-2. Importantly, R5020-activated PRB abolished the effect of estrogen. This intense anti-estrogenic effect was mediated by marked downregulation of ERα and pioneer factor FOXA1, leading to diminished chromatin-associated ERα and FOXA1 and estrogen-induced target gene expression. In conclusion, high levels of agonist-activated PRB in breast cancer cells can be strongly anti-tumoral and anti-estrogenic despite the initial unproductive cell cycle acceleration. Repression of ERα and FOXA1 expression is a major mechanism for the strong anti-estrogenic effect.

Abstract 3356: Comparative analysis of approved and undertrial SERDs in estrogen receptor-α (ERα): An in-silico approach

Abstract Background: Despite recent advancements in early detection and treatment, breast cancer is the second most common cancer affecting women globally, with 11.7% of total new cases. The disease is the fifth leading cause of cancer mortality worldwide, with 685,000 deaths in 2020. Approximately 75% of all breast cancer are ERα positive and resistant to current therapies like aromatase Inhibitors (AIs) and selective receptors modulators (SERMs). The selective estrogen receptor degrader (SERDs) ability to antagonize and degrade ERα makes them promising therapeutic agents for hormone-refractory breast cancer treatment. Fulvestrant is the only SERD with steroidal core currently approved for ER-positive breast cancer treatment. However, its poor physicochemical properties limit its efficacy. Many non-steroidal SERDs such as Amcenestrant, Elacestrant, Camizestrant, Giredestrant, and LSZ102 are under various advanced development stages. However, their long-term efficacy is yet to be established. Our in- silico studies aim to evaluate and compare multiple SERDs (approved and under trial) in terms of their shape similarity, binding mechanism, and stability with ERα receptor. Methods: Present work focuses on evaluating and comparing the shape similarity and electrostatic potential of various SERDs with respect to ERα endogenous ligand; estradiol (E2). Docking studies were performed to understand the binding mode of selected SERDs within the active site of ERα. Additional parameters like root-mean square-square deviation (RMSD), root-mean square-fluctuation (RMSF), pocket volume fluctuations, and protein-ligand binding energy were calculated using Molecular Dynamics (MD) simulation techniques to understand the stability and binding mechanism of various SERDs. Result: Among various evaluated SERDs, Fulvestrant shares the highest whereas Elacestrant shares the lowest shape similarity with E2. All docked SERDs cores occupy the same binding pocket and tend to bind in a similar fashion as E2, with their tail protruding towards helix 12 (H12). As observed interactions with H12 are mainly responsible for ERα downregulation. However, in MD studies analysis, it was found that non-steroidal core molecules were less stable and showed more fluctuations (within active site) than steroidal core molecule (Fulvestrant). Moreover, protein-ligand binding energy for Fulvestrant was found to be lower which corresponds to its higher stability with ERα. Conclusion: The current study helps us to understand the binding mechanism, antagonism, and downregulation of multiple SERDs, among which Fulvestrant showed the highest binding affinity towards ERα (due to its highest shape similarity with E2) and can interact with and disrupt H12 (due to its long tail) which is a critical component of SERD. This knowledge could further be used to develop novel SERDs for ESR1 mutant and HR-positive breast cancer treatment. Citation Format: Vishal Unadkat, Shishir Rohit, Parva Purohit, Chirag Mehta, Vishal Goswami, Mahesh Barmade, Sonam Sinha, Ganesh Sangle. Comparative analysis of approved and undertrial SERDs in estrogen receptor-α (ERα): An in-silico approach [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 3356.

Andrographolide Exhibits Anticancer Activity against Breast Cancer Cells (MCF-7 and MDA-MB-231 Cells) through Suppressing Cell Proliferation and Inducing Cell Apoptosis via Inactivation of ER-α Receptor and PI3K/AKT/mTOR Signaling.

Breast cancer is the most common cancer among women worldwide. Chemotherapy followed by endocrine therapy is the standard treatment strategy after surgery or radiotherapy. However, breast cancer is highly resistant to the treatments leading to the recurrence of breast cancer. As a result, the development of alternative medicines derived from natural plants with fewer side effects is being emphasized. Andrographolide isolated from Andrographis paniculata is one of the potential substances with anti-cancer properties in a variety of cell types, including breast cancer cells. This study aims to investigate the anti-cancer effects of andrographolide in breast cancer cells by evaluating cell viability and apoptosis as well as its underlying mechanisms through estrogen receptor (ER)-dependent and PI3K/AKT/mTOR signaling pathways. Cell viability, cell apoptosis, mRNA or miRNA, and protein expression were examined by MTT assay, Annexin V-FITC, qRT-PCR, and Western blot analysis, respectively. MCF-7 and MDA-MB-231 cell viability was reduced in a concentration- and time-dependent manner after andrographolide treatment. Moreover, andrographolide induced cell apoptosis in both MCF-7 and MDA-MB-231 cells by inhibiting Bcl-2 and enhancing Bax expression at both mRNA and protein levels. In MCF-7 cells, the ER-positive breast cancer, andrographolide showed an inhibitory effect on cell proliferation through downregulation of ERα, PI3K, and mTOR expression levels. Andrographolide also inhibited MDA-MB-231 breast cancer cell proliferation via induction of cell apoptosis. However, the inhibition of MCF-7 and MDA-MB-231 cell proliferation of andrographolide treatment did not disrupt miR-21. Our findings showed that andrographolide possesses an anti-estrogenic effect by suppressing cell proliferation in MCF-7 cells. The effects were comparable to those of the anticancer drug fulvestrant in MCF-7 cells. This study provides new insights into the anti-cancer effect of andrographolide on breast cancer and suggests andrographolide as a potential alternative from the natural plant for treating breast cancer types that are resistant to tamoxifen and fulvestrant.

Defective Signalling of the BRCA1 Neighbouring gene, NBR2, leads to ER-? Negative tumours in breast cancer xenograft mouse models

Majority of breast and ovarian cancer treatment modalities are based on endocrine therapies like antiestrogens which are dependent on the hormone receptor status of tumours. Although BRCA1 is a major regulator of Estrogen Receptor (ER-α), BRCA1 mutations are largely limited to hereditary cases. Here, we show the role of NBR2 (neighbour of BRCA1) in regulating ER-α. We demonstrate a positive correlation between NBR2 &amp; ESR1 in TCGA datasets. Further, the study revealed that shRNA-mediated knockdown of NBR2 led to the downregulation of ER-α in breast cancer cells, MCF7. Finally, the downregulation of ER-α in NBR2 knockdown xenograft tumours (in female NSG mice), which showed higher invasive properties than wild type tumours was demonstrated. Thus, we concluded that in ER-α negative tumours with NBR2 deficiency, biguanides such as metformin and phenformin, which are reported to have a better efficacy under NBR2 deficient conditions, could serve as more suitable alternatives to antiestrogens.

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.

Control of ER-positive breast cancer by ERα expression inhibition, apoptosis induction, cell cycle arrest using semisynthetic isoeugenol derivatives

New semi-synthetic effective and safe anticancer agents isoeugenol derivatives were synthesized, characterized, and screened for their cytotoxic activity against MCF-7. Moreover, their selective cytotoxicity was assessed against MCF-10A. Three derivatives, 2, 8 and 10 were significantly more active than the reference drug 5-FU with IC50 values of 6.59, 8.07 and 9.63 and 30.93 μM, respectively. Also interestingly, these derivatives demonstrated some degree of selectivity to cancer cells over normal cells. Furthermore, derivative 2 was subjected to other in vitro experiments against MCF-7 where it inhibited colony formation by 87.5% and lowered ERα concentration to 395.7 pg/mL compared to 1129 pg/mL in untreated control cells. In continuation of the investigation, the apoptotic activity of compound 2, was assessed where it significantly enhanced total apoptotic cell death by 9.16-fold (18.70% compared to 1.64% for the untreated MCF-7 control cells) and arrested the cell cycle at the G2/M phase. Furthermore, the molecular mechanism of apoptotic activity was investigated at both the gene (RT-PCR) and protein (western plotting) levels where upregulation of pro-apoptotic and down regulation of anti-apoptotic genes was detected. Additionally, compound 2 treatment enhanced the antioxidant (GSH, CAT, SOD) activities. Finally, in vivo experiments verified the effective anticancer activity of compound 2 through inhibition of tumor proliferation by 47.6% compared to 22.9% for 5-FU and amelioration of the hematological, biochemical, and histopathological examinations near normal. In effect, compound 2 can be viewed as a promising semi-synthetic derivative of isoeugenol with some degree of selectivity for management of breast cancer through apoptotic induction and ERα downregulation.

Mice Uterine Stem Cells are Affected by Neonatal Endocrine Disruption & Initiate Uteropathies in Adult Life Independent of Circulatory Ovarian Hormones.

It is generally believed that ovarian hormones regulate uterine functions and their altered levels result in various uteropathies like non-receptive uterus, endometrial hyperplasia, adenomyosis, endometriosis, leiomyomas and cancer. Uterus harbors two populations of stem cells including pluripotent, very small embryonic-like stem cells (VSELs) and tissue-specific progenitors (endometrial stem cells, EnSCs). Unlike endometrial mesenchymal stem/ stromal cells, VSELs/EnSCs express ERα, ERβ and PR which makes them directly vulnerable to perinatalendocrine insults. Present study was undertaken to evaluate whether uteropathies occur due to altered hormones and/or intrinsic changes in stem/progenitor cells. Mice pups, exposed to estradiol (20µg/pup/day) on postnatal days 3-7 or vehicle, were subjected to bilateral ovariectomy on day 30 and later exposed sequentially to estradiol and progesterone resulting in receptive uterus in control mice. Despite similar hormonal exposure, endocrine disruption resulted in non-receptive uterus with noticeable endometrial and myometrial hyperplasia and up-regulation of stem cell markers (Oct-4A, Oct-4, Sox2, Nanog). Glands were poorly formed and 'defective' epithelial progenitors were found disseminated into myometrium and blood vessels revealing how adenomyosis and endometriosis possibly initiate. Progesterone resistance and estradiol dominance due to downregulation of Erα & Pr and upregulation of Erβ transcripts was observed in both intact uterus and stem cells enriched from uterus. Transcripts specific for DNA mismatch repair axis (Pcna, NP95 and Dnmt1), repair enzymes (Brca-1, Rad51 and Mlh1) were dysregulated whereas Ki67 was ten-folds increased suggestive of genomic instability. Study reveals role of stem cells in initiating uteropathies during adult life independent of circulatory ovarian hormones. Endocrine disruption affects tissue resident stem/progenitor cells (VSELs/EnSCs) in both endometrium and myometrium, result in epithelial cells hyperplasia, non-receptive endometrium, adenomyosis and defective stem cells and epithelial progenitors were detected in the perimetrium from where they can mobilize to ectopic sites to initiate endometriosis. Study shows stem cell basis for various uteropathies. VSEL: Very small embryonic like stem cell; EnSC: Endometrial stem cell; E + P: Estradiol + Progesterone; E: Endometrium; P: Perimetrium; M: Myometrium; ACD: Asymmetrical cell division; SCD: Symmetrical cell division; CE: Clonal expansion; G: Gland; S: Stromal cell; US: Undifferentiated stromal cell; LE: Luminal epithelium; GE: Glandular epithelium; EP: Epithelial progenitors; SMC: Spindle-shaped myometrial cell; OMC: Oval-shaped myometrial cell.

Crosstalk between progesterone receptor membrane component 1 and estrogen receptor α promotes breast cancer cell proliferation

Progesterone (P4) and estradiol (E2) have been shown to stimulate and regulate breast cancer proliferation via classical nuclear receptor signaling through progesterone receptor (PR) and estrogen receptor α (ERα), respectively. However, the basis of communication between PR/ERα and membrane receptors remains largely unknown. Here, we aim to identify classical and nonclassical endocrine signaling mechanisms that can alter cell proliferation through a possible crosstalk between PR, ERα, and progesterone receptor membrane component 1 (PGRMC1), a membrane receptor frequently observed in breast cancer cells. While P4 and E2 treatment increased cell proliferation of ER+/PR+/PGRMC1 overexpressing breast cancer cells, silencing ERα and PR or treatment with selective estrogen receptor modulator (SERM) tamoxifen, or (PR-antagonist) RU-486 decreased cell proliferation. All four treatments rapidly altered PGRMC1 mRNA levels and protein expression. Furthermore, P4 and E2 treatments rapidly activated EGFR a known interacting partner of PGRMC1 and its downstream signaling. Interestingly, downregulation of ERα by tamoxifen and ERα silencing decreased the expression levels of PGRMC1 with no repercussions to PR expression. Strikingly PGRMC1 silencing decreased ERα expression irrespective of PR. METABRIC and TCGA datasets further demonstrated that PGRMC1 expression was comparable to that of ERα in Luminal A and B breast cancers. Targeting of PR, ERα, and PGRMC1 confirmed that a crosstalk between classical and nonclassical signaling mechanisms exists in ER+ breast cancer cells that could enhance the growth of ER+/PR+/PGRMC1 overexpressing tumors.