The role of ERα36 in cell type-specific functions of estrogen and cancer development

Expression Significance of Estrogen Receptor ER-α36 in Breast Cancer Treated by Chemotherapy: A Meta-Analysis

Estrogen receptor (ER) is a molecular marker and target for diagnosing and treating breast cancer (BC). ER-α36, a novel estrogen receptor subtype, involved in the proliferation, differentiation, metastasis, and invasion of tumor cells. It is closely linked to the progression of various cancers. Therefore, studying ER is of high significance in treating BC. In this study, we will investigate the changes in the expression level of ER-α36 in patients with BC treated by chemotherapy through meta-analysis, so as to evaluate the clinical value of ER-α36 in the prognosis of BC treated by chemotherapy. English databases such as PubMed, Web of Science, Embase, and The Cochrane Library were searched to retrieve the articles published from the establishment of the database to April 2023. The keywords included chemotherapy, neoadjuvant chemotherapy, breast cancer, estrogen receptor alpha, and ER-α36. Five suitable studies, encompassing 636 patients, were ultimately selected. The meta-analysis results revealed that, following the chemotherapy, the analysis of ER-α36 positive cases yielded an Odds Ratio (OR) of 0.42, a 95% confidence interval (CI) of 0.28-0.64 (Z = 4.00, P < 0.0001). Additionally, the analysis of cases exhibiting remission in BC demonstrated an OR of 2.22 (95% CI = 1.40-3.50, Z = 3.40, P = 0.0007). Compared to patients receiving single chemotherapy agents or those untreated with chemotherapy, the combined use of multiple chemotherapy drugs can significantly reduce the levels of ER-α36 in BC patients, enhancing the remission rate of BC. ER-α36 can serve as a critical indicator for assessing the prognosis of BC following chemotherapy.

Targeting epidermal growth factor receptor and its downstream signaling pathways by natural products: A mechanistic insight

The epidermal growth factor receptor (EGFR) is a transmembrane receptor tyrosine kinase (RTK) that maintains normal tissues and cell signaling pathways. EGFR is overactivated and overexpressed in many malignancies, including breast, lung, pancreatic, and kidney. Further, the EGFR gene mutations and protein overexpression activate downstream signaling pathways in cancerous cells, stimulating the growth, survival, resistance to apoptosis, and progression of tumors. Anti-EGFR therapy is the potential approach for treating malignancies and has demonstrated clinical success in treating specific cancers. The recent report suggests most of the clinically used EGFR tyrosine kinase inhibitors developed resistance to the cancer cells. This perspective provides a brief overview of EGFR and its implications in cancer. We have summarized natural products-derived anticancer compounds with the mechanistic basis of tumor inhibition via the EGFR pathway. We propose that developing natural lead molecules into new anticancer agents has a bright future after clinical investigation.

Deciphering Glioblastoma: Fundamental and Novel Insights into the Biology and Therapeutic Strategies of Gliomas

Gliomas constitute a diverse and complex array of tumors within the central nervous system (CNS), characterized by a wide range of prognostic outcomes and responses to therapeutic interventions. This literature review endeavors to conduct a thorough investigation of gliomas, with a particular emphasis on glioblastoma (GBM), beginning with their classification and epidemiological characteristics, evaluating their relative importance within the CNS tumor spectrum. We examine the immunological context of gliomas, unveiling the intricate immune environment and its ramifications for disease progression and therapeutic strategies. Moreover, we accentuate critical developments in understanding tumor behavior, focusing on recent research breakthroughs in treatment responses and the elucidation of cellular signaling pathways. Analyzing the most novel transcriptomic studies, we investigate the variations in gene expression patterns in glioma cells, assessing the prognostic and therapeutic implications of these genetic alterations. Furthermore, the role of epigenetic modifications in the pathogenesis of gliomas is underscored, suggesting that such changes are fundamental to tumor evolution and possible therapeutic advancements. In the end, this comparative oncological analysis situates GBM within the wider context of neoplasms, delineating both distinct and shared characteristics with other types of tumors.

Small molecule inhibitor targeting the Hsp70-Bim protein-protein interaction in estrogen receptor-positive breast cancer overcomes tamoxifen resistance

INTRODUCTION

Estrogen receptor (ER) positive patients compromise about 70% of breast cancers. Tamoxifen, an antagonist of ERα66 (the classic ER), is the most effective and the standard first-line drug. However, its efficacy is limited by the development of acquired resistance.

METHODS

A specific inhibitor of Hsp70-Bim protein-protein interaction (PPI), S1g-2, together with an inhibitor of Hsp70-Bag3 PPI, MKT-077 and an ATP-competitive inhibitor VER155008, were used as chemical tools. Cell viability assays, co-immunoprecipitation and gene knockdown were used to investigate the role of Hsp70 in tamoxifen resistance. A xenograft model was established in which tamoxifen-resistant breast cancer (MCF-7/TAM-R) cells maintained in the presence of 5 μM tamoxifen were subcutaneously inoculated. The anti-tumor efficiency of S1g-2 was measured after a daily injection of 0.8 mg/kg for 14 days.

RESULTS

It was revealed that Hsp70-Bim PPI protects ERα-positive breast cancer from tamoxifen-induced apoptosis through binding and stabilizing ERα36, rather than ERα66, resulting in sustained EGFR mRNA and protein expression. Disruption of Hsp70-Bim PPI and downregulation of ERα36 expression in tumor samples are consistent with the in vitro functions of S1g-2, resulting in about a three-fold reduction in tumor volume.

CONCLUSIONS

The in vivo activity and safety of S1g-2 illustrated that it is a potential strategy for Hsp70-Bim disruption to overcome tamoxifen-resistant ER-positive breast cancer.

Progress in the Understanding of Estrogen Receptor Alpha Signaling in Triple-Negative Breast Cancer: Reactivation of Silenced ER-α and Signaling through ER-α36

Triple-negative breast cancer (TNBC) is an aggressive tumor that accounts for approximately 15% of total breast cancer cases. It is characterized by poor prognosis and high rate of recurrence compared to other types of breast cancer. TNBC has a limited range of treatment options that include chemotherapy, surgery, and radiation due to the absence of estrogen receptor alpha (ER-α) rendering hormonal therapy ineffective. However, possible targets for improving the clinical outcomes in TNBC exist, such as targeting estrogen signaling through membranous ER-α36 and reactivating silenced ER-α. It has been shown that epigenetic drugs such as DNA methyltransferase and histone deacetylase inhibitors can restore the expression of ER-α. This reactivation of ER-α, presents a potential strategy to re-sensitize TNBC to hormonal therapy. Also, this review provides up-to-date information related to the direct involvement of miRNA in regulating the translation of ER-α mRNA. Specific epi-miRNAs can regulate ER-α expression indirectly by post-transcriptional targeting of mRNAs of enzymes that are involved in DNA methylation and histone deacetylation. Furthermore, ER-α36, an alternative splice variant of ER-α66, is highly expressed in ER-negative breast tumors and activates MAPK/ERK pathway, promoting cell proliferation, escaping apoptosis, and enhancing metastasis. In the future, these recent advances may be helpful for researchers working in the field to obtain novel treatment options for TNBC, utilizing epigenetic drugs and epi-miRNAs that regulate ER-α expression. Also, there is some evidence to suggest that drugs that decrease the expression of ER-α36 may be effective in treating TNBC.

Proximity hybridization regulated dual-mode ratiometric biosensor for estriol detection in pregnancy serum

Sensitive and accurate determination of estriol level is vastly significant for the fetal growth and development. Herein, we constructed a dual-mode ratiometric biosensor for estriol assay combining the competitive immunoreaction, proximity hybridization with a two-step resonance energy transfer (RET) strategy. Estriol antibody and goat anti-rabbit antibody labeled DNA probes (Ab1-DNA1-Pt NPs and Ab2-DNA2) both hybridized with silver nanoclusters labeled DNA strands (H1-Ag NCs). Thus, the formed proximity hybridization enabled the occurrence of fluorescence RET (FL-RET, as the primary RET) between Ag NCs (donor) and Pt NPs (acceptor), quenching FL intensity of Ag NCs (FL off). When target estriol existed, the competitive reaction of Ab1-DNA1-Pt NPs with estriol and Ab2-DNA2 avoided the proximity hybridization. Then, the estriol-dependent H1-Ag NCs quenched electrochemiluminescence (ECL) emission of CdS quantum dots (CdS QDs, ECL off), generating ECL-RET (as the second RET). Consequently, according to the reverse changes of FL and ECL responses, this sensor realized the quantification of estriol from 1 to 100 ng/mL. Moreover, satisfactory results were achieved while testing estriol in pregnancy serum specimens, suggesting that the system is promising for potential application in samples analysis.

A review of tamoxifen administration regimen optimization for Cre/loxp system in mouse bone study

Gene knockout is a technique routinely used in basic experimental research, particularly in mouse skeletal and developmental studies. Tamoxifen-induced Cre/loxp system is known for its temporal and spatial precision and commonly utilized by researchers. However, tamoxifen has been shown its side effects on affecting the phenotype of mouse bone directly. This review aimed to optimize tamoxifen administration regimens including its dosage and duration, to identify an optimal induction strategy that minimizes potential side effects while maintaining recombination efficacy. This study will help researchers in designing gene knockout experiments in bone when using tamoxifen.

The location of estrogen receptor variant ER-α36 is associated with the invasion of glioblastoma

Glioblastoma (GBM) is the most common central nervous system tumor and is associated with poor outcomes. There have been no significant improvements in GBM mortality in recent decades. ER-α36 is a variant of ER-α66 that may be involved in carcinoma growth and proliferation via genomic and nongenomic mechanisms. This variant might play an essential role in tamoxifen resistance of several tumors. Previously, our laboratory found that ER-α36 is expressed in GBM and participates in proliferation; nevertheless, the role of ER-α36 in GBM invasion remains unknown. This study aimed to determine the effects of the ER-α36 modulator SNG162 on GBM growth and invasion. U251 cells, U87cells, and U87-36KD cells with knockdown of ER-α36 expression were cultured under the two-dimensional and the three-dimensional (3D) environments. GBM cells growth was examined by cell counting, flow cytometry, western blot, and MTT assays. Invasiveness was measured using confocal microscopy in the 3D environment. Growth of U87 cells with downregulated EGFR and ER-α36 expression was significantly reduced after treatment with 1 µM, 3 µM, and 5 µM of SNG162; growth inhibition in U251 cells was more potent than in U87 cells, although the expression level of ER-α36 in U251 cells was lower than in U87 cells. We found that 1 μM SNG162 suppressed E₂-induced MAPK/ERK pathway activation in U87 cells. We also showed that SNG162 inhibited U87 cells invasion; however, it did not significantly affect U251 and U87-36KD cells invasion using the 3D culture method. Finally, we determined that ER-α36 was expressed in the nucleus of invading GBM cells, and SNG162 significantly inhibited the expression of ER-α36 in these cells. SNG162 inhibited the expression of EGFR on cell membranes of non-invasive GBM cells. These results suggest that SNG162 could be a therapeutic agent for GBM by targeting ER-α36.

Epigenetic Modifications by Estrogen and Androgen in Alzheimer's Disease

For the development and maintenance of neuron networks in the brain, epigenetic mechanisms are necessary, as indicated by recent findings. This includes some of the high-order brain processes, such as behavior and cognitive functions. Epigenetic mechanisms could influence the pathophysiology or etiology of some neuronal diseases, altering disease susceptibility and therapy responses. Recent studies support epigenetic dysfunctions in neurodegenerative and psychiatric conditions, such as Alzheimer's disease (AD). These dysfunctions in epigenetic mechanisms also play crucial roles in the transgenerational effects of the environment on the brain and subsequently in the inheritance of pathologies. The possible role of gonadal steroids in the etiology and progression of neurodegenerative diseases, including Alzheimer's disease, has become the subject of a growing body of research over the last 20 years. Recent scientific findings suggest that epigenetic changes, driven by estrogen and androgens, play a vital role in brain functioning. Therefore, exploring the role of estrogen and androgen-based epigenetic changes in the brain is critical for the deeper understanding of AD. This review highlights the epigenetic modifications caused by these two gonadal steroids and the possible therapeutic strategies for AD.

The essential role of YAP in ERα36-mediated proliferation and the epithelial-mesenchymal transition in MCF-7 breast cancer cells

Purpose: Most breast cancers are hormone-receptor-positive, and thus the first-line therapy for them is an anti-estrogen medication such as tamoxifen. If metastasis occurs or resistance to tamoxifen develops, the 5-year survival rates for breast cancer patients significantly decrease. Hence, a better understanding of the molecular mechanisms that contribute to breast cancer aggressiveness is of great importance. ERα36 is an estrogen receptor variant that is known to be upregulated in breast cancer patients receiving tamoxifen treatment or in triple-negative breast cancer cells. However, the specific molecular mechanism underlying ERα36-induced tamoxifen-resistance is not yet fully understood. Methods: ERα36-overexpressing MCF-7 cells were constructed by either plasmid transfection using ERα36 vector or retroviral infection using ERα36-V5-His vector. Target-gene expression was assessed by Western blot analysis and real-time PCR, and YAP activation was evaluated by luciferase assays and immunofluorescence. Cell proliferation and formation of three-dimensional spheroids were evaluated using the IncuCyte S3 Live Cell Analysis System. Results: We found that the expression patterns of Hippo signaling-related genes were significantly changed in ERα36-overexpressing MCF-7 cells compared to MCF-7 cells, which were also similarly observed in tamoxifen-resistant MCF-7 cells. Specifically, the protein expression level and activity of YAP, the core downstream protein of the Hippo pathway, were significantly increased in ERα36-overexpressing MCF-7 cells compared with MCF-7 cells. The aggressive phenotypes acquired by ERα36 overexpression in MCF-7 cells were destroyed by YAP knockout. On this basis, we propose that ERα36 regulates YAP activity by a new mechanism involving Src kinase. Conclusion: Our results suggest that YAP targeting may be a new therapeutic approach to the treatment of advanced breast cancers overexpressing ERα36.

Hypermethylation of the Promoter of miR-338-5p Mediates Aberrant Expression of ETS-1 and Is Correlated With Disease Severity Of Astrocytoma Patients

The pro-oncogene ETS-1 (E26 transformation-specific sequence 1) is a key regulator of the proliferation and invasion of cancer cells. The present work examined the correlation of the aberrant expression of ETS-1 with histological or clinical classification of astrocytoma: grade I (pilocytic astrocytoma), grade II (diffuse astrocytoma), grade III (anaplastic astrocytoma), and grade IV (glioblastoma multiforme). MicroRNA, miR-338-5p, was predicted by an online tool (miRDB) to potentially target the 3’ untranslated region of ETS-1; this was confirmed by multi-assays, including western blot experiments or the point mutation of the targeting sites of miR-338-5p in ETS-1’s 3’untralation region (3’UTR). The expression of miR-338-5p was negatively associated with that of ETS-1 in astrocytoma, and deficiency of miR-338-5p would mediate aberrant expression of ETS-1 in astrocytoma. Mechanistically, hypermethylation of miR-338-5p by DNA methyltransferase 1 (DNMT1) resulted in repression of miR-338-5p expression and the aberrant expression of ETS-1. Knockdown or deactivation of DNMT1 decreased the methylation rate of the miR-338-5p promoter, increased the expression of miR-338-5p, and repressed the expression of ETS-1 in astrocytoma cell lines U251 and U87. These results indicate that hypermethylation of the miR-338-5p promoter by DNMT1 mediates the aberrant expression of ETS-1 related to disease severity of patients with astrocytoma.

Non-genomic signaling of steroid receptors in cancer

Steroid receptors (SRs) are members of the nuclear receptor family, which are ligand-activated transcription factors. SRs regulate many physiological functions including development and reproduction, though they can also be involved in several pathologies, especially cancer. Highly controlled cellular responses to steroids involve transcriptional regulation (genomic activity) combined with direct activation of signaling cascades (non-genomic activity). Non-genomic signaling has been extensively studied in cancer, mainly in breast cancer for ER and PR, and prostate cancer for AR. Even though most of the studies have been conducted in cells, some of them have been confirmed in vivo, highlighting the relevance of this pathway in cancer. This review provides an overview of the current and emerging knowledge on non-genomic signaling with a focus on breast and prostate cancers and its clinical relevance. A thorough understanding of ER, PR, AR and GR non-genomic pathways may open new perspectives for the development of therapeutic strategies.

Lost but Not Least-Novel Insights into Progesterone Receptor Loss in Estrogen Receptor-Positive Breast Cancer

Estrogen receptor α (ERα) and progesterone receptor (PgR) are crucial prognostic and predictive biomarkers that are usually co-expressed in breast cancer (BC). However, 12-24% of BCs present ERα(+)/PgR(-) phenotype at immunohistochemical evaluation. In fact, BC may either show primary PgR(-) status (in chemonaïve tumor sample), lose PgR expression during neoadjuvant treatment, or acquire PgR(-) phenotype in local relapse or metastasis. The loss of PgR expression in ERα(+) breast cancer may signify resistance to endocrine therapy and poorer outcomes. On the other hand, ERα(+)/PgR(-) BCs may have a better response to neoadjuvant chemotherapy than double-positive tumors. Loss of PgR expression may be a result of pre-transcriptional alterations (copy number loss, mutation, epigenetic modifications), decreased transcription of the PGR gene (e.g., by microRNAs), and post-translational modifications (e.g., phosphorylation, sumoylation). Various processes involved in the down-regulation of PgR have distinct consequences on the biology of cancer cells. Occasionally, negative PgR status detected by immunohistochemical analysis is paradoxically associated with enhanced transcriptional activity of PgR that might be inhibited by antiprogestin treatment. Identification of the mechanism of PgR loss in each patient seems challenging, yet it may provide important information on the biology of the tumor and predict its responsiveness to the therapy.

Potentiating Therapeutic Effects of Epidermal Growth Factor Receptor Inhibition in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is a subset of breast cancer with aggressive characteristics and few therapeutic options. The lack of an appropriate therapeutic target is a challenging issue in treating TNBC. Although a high level expression of epidermal growth factor receptor (EGFR) has been associated with a poor prognosis among patients with TNBC, targeted anti-EGFR therapies have demonstrated limited efficacy for TNBC treatment in both clinical and preclinical settings. However, with the advantage of a number of clinically approved EGFR inhibitors (EGFRis), combination strategies have been explored as a promising approach to overcome the intrinsic resistance of TNBC to EGFRis. In this review, we analyzed the literature on the combination of EGFRis with other molecularly targeted therapeutics or conventional chemotherapeutics to understand the current knowledge and to provide potential therapeutic options for TNBC treatment.

miR-27-3p Enhances the Sensitivity of Triple-Negative Breast Cancer Cells to the Antitumor Agent Olaparib by Targeting PSEN-1, the Catalytic Subunit of Γ-Secretase

Olaparib has been used in the treatment of triple-negative breast cancer (TNBC) with BRCA mutations. In the present study, we demonstrated the effect of miR-27-3p on the γ-secretase pathway by regulating the sensitivity of TNBC cells to olaparib. miR-27-3p, a microRNA with the potential to target PSEN-1, the catalytic subunit of γ-secretase mediating the second step of the cleavage of the Notch protein, was identified by the online tool miRDB and found to inhibit the expression of PSEN-1 by directly targeting the 3'-untranslated region (3'-UTR) of PSEN-1. The overexpression of miR-27-3p inhibited the activation of the Notch pathway via the inhibition of the cleavage of the Notch protein, mediated by γ-secretase, and, in turn, enhanced the sensitivity of TNBC cells to the antitumor agent olaparib. Transfection with PSEN-1 containing mutated targeting sites for miR-27-3p or the expression vector of the Notch protein intracellular domain (NICD) almost completely blocked the effect of miR-27-3p on the Notch pathway or the sensitivity of TNBC cells to olaparib, respectively. Therefore, our results suggest that the miR-27-3p/γ-secretase axis participates in the regulation of TNBC and that the overexpression of miR-27-3p represents a potential approach to enhancing the sensitivity of TNBC to olaparib.

Distribution and Effects of Estrogen Receptors in Prostate Cancer: Associated Molecular Mechanisms

Estrogens are hormones that have been extensively presented in many types of cancer such as breast, uterus, colorectal, prostate, and others, due to dynamically integrated signaling cascades that coordinate cellular growth, differentiation, and death which can be potentially new therapeutic targets. Despite the historical use of estrogens in the pathogenesis of prostate cancer (PCa), their biological effect is not well known, nor their role in carcinogenesis or the mechanisms used to carry their therapeutic effects of neoplastic in prostate transformation. The expression and regulation of the estrogen receptors (ERs) ERα, ERβ, and GPER stimulated by agonists and antagonists, and related to prostate cancer cells are herein reviewed. Subsequently, the structures of the ERs and their splice variants, the binding of ligands to ERs, and the effect on PCa are provided. Finally, we also assessed the contribution of molecular simulation which can help us to search and predict potential estrogenic activities.