Estrogen receptor alpha-36 (ER-α36): A new player in human breast cancer

Estradiol induces bone osteolysis in triple-negative breast cancer via its membrane-associated receptor ERα36

Triple-negative breast cancer (TNBC) is thought to be an estradiol-independent, hormone therapy-resistant cancer because of lack of estrogen receptor alpha 66 (ERα66). We identified a membrane-bound splice variant, ERα36, in TNBC cells that responds to estrogen (E2) and may contribute to bone osteolysis. We demonstrated that the MDA-MB-231 TNBC cell line, which expresses ERα36 similarly to MCF7 cells, is responsive to E2, forming osteolytic tumors in vivo. MDA-MB-231 cells activate osteoclasts in a paracrine manner. Conditioned media (CM) from MDA-MB-231 cells treated with bovine serum albumin-bound E2 (E2-BSA) increased activation of human osteoclast precursor cells; this was blocked by addition of anti-ERα36 antibody to the MDA-MB-231 cultures. Osteoclast activation and bone resorption genes were elevated in RAW 264.7 murine macrophages following treatment with E2-BSA-stimulated MDA-MB-231 CM. E2 and E2-BSA increased phospholipase C (PLC) and protein kinase C (PKC) activity in MDA-MB-231 cells. To examine the role of ERα36 signaling in bone osteolysis in TNBC, we used our bone-cancer interface mouse model in female athymic homozygous Foxn1nu mice. Mice with MDA-MB-231 tumors and treated with tamoxifen (TAM), E2, or TAM/E2 exhibited increased osteolysis, cortical bone breakdown, pathologic fracture, and tumor volume; the combined E2/TAM group also had reduced bone volume. These results suggest that E2 increased osteolytic lesions in TNBC through a membrane-mediated PLC/PKC pathway involving ERα36, which was enhanced by TAM, demonstrating the role of ERα36 and its membrane-associated signaling pathway in bone tumors. This work suggests that ERα36 may be a potential therapeutic target in patients with TNBC.

Laryngeal Cancer Cells Metabolize 25-Hydroxyvitamin D3 and Respond to 24R,25-dihydroxyvitamin D3 via a Mechanism Dependent on Estrogen Receptor Levels

Studies have evaluated vitamin D3's therapeutic potential in estrogen-responsive cancers, with conflicting findings. We have shown that the proliferation of breast cancer cells is regulated by 24R,25-dihydroxyvitamin D3 (24R,25(OH)2D3) depending on estrogen receptor alpha 66 (ERα66) expression, suggesting that this could also be the case for estrogen-sensitive laryngeal cancer cells. Accordingly, we examined levels of ERα isoforms in ERα66-positive UM-SCC-12 and ERα66-negative UM-SCC-11A cells and their response to 24R,25(OH)2D3. 24R,25(OH)2D3 stimulated proliferation, increased the expression of metastatic markers, and inhibited apoptosis in UM-SCC-12 cells while having the opposite effect in UM-SCC-11A cells. To evaluate if vitamin metabolites could act via autocrine/paracrine mechanisms, we assessed the expression, protein levels, and activity of vitamin D3 hydroxylases CYP24A1 and CYP27B1. Both cell types expressed both mRNAs; but the levels of the enzymes and their activities were differentially regulated by estrogen. ERα66-negative UM-SCC-11A cells produced more 24,25(OH)2D3 than UM-SCC-12 cells, but comparable levels of 1,25(OH)2D3 when treated with 25(OH)D3 These results suggest that the regulation of vitamin D3 metabolism in laryngeal cancer cells is modulated by ERα66 expression, and support a role for 24R,25(OH)2D3 as an autocrine/paracrine regulator of laryngeal cancer. The local metabolism of 25(OH)D3 should be considered when determining the potential of vitamin D3 in laryngeal cancer.

ER-α36 is involved in calycosin inhibition of IL-6 production in macrophages

The tumour microenvironment (TME) is crucial for tumour development and progression. Tumour-associated macrophages (TAMs) in the TME can promote tumour progression and metastasis by releasing cytokines, such as IL-6. Calycosin, a phytoestrogen that is one of the active compounds in Radix Astragali, has been shown to inhibit tumour growth and metastasis. However, the underlying mechanism by which calycosin inhibits tumour growth remains unclear. Thus, this study aimed to investigate the effect of calycosin on IL-6 production in peripheral blood mononuclear cell (PBMC)- and THP-1-derived macrophages and explore its potential mechanisms using co-immunoprecipitation, western blotting, immunofluorescence, chromatin immunoprecipitation and luciferase assays. We found that calycosin treatment substantially upregulated the expression of ER-α36, a variant of the ER, and reduced IL-6 production in macrophages. Mechanistically, ER-α36 physically interacted with NF-κBp65 and retained p65 in the cytoplasm to attenuate NF-κB function as an IL-6 transcriptional inducer. In conclusion, our result indicated that calycosin inhibited IL-6 production by enhancing ER-α36 expression and its interaction with p65, which attenuated NF-κB function as an IL-6 inducer. Therefore, calycosin can be developed as an effective agent for cancer therapy by targeting TAMs.

The role of sex hormones and receptors in HBV infection and development of HBV-related HCC

Gender disparity in hepatitis B virus (HBV)-related diseases has been extensively documented. Epidemiological studies consistently reported that males have a higher prevalence of HBV infection and incidence of hepatocellular carcinoma (HCC). Further investigations have revealed that sex hormone-related signal transductions play a significant role in gender disparity. Sex hormone axes showed significantly different responses to virus entry and replication. The sex hormones axes change the HBV-specific immune responses and antitumor immunity. Additionally, Sex hormone axes showed different effects on the development of HBV-related disease. But the role of sex hormones remains controversial, and researchers have not reached a consensus on the role of sex hormones and the use of hormone therapies in HCC treatment. In this review, we aim to summarize the experimental findings on sex hormones and provide a comprehensive understanding of their roles in the development of HCC and their implications for hormone-related HCC treatment.

Roles of estrogen receptor α in endometrial carcinoma (Review)

Endometrial carcinoma (EC) is a group of endometrial epithelial malignancies, most of which are adenocarcinomas and occur in perimenopausal and postmenopausal women. It is one of the most common carcinomas of the female reproductive system. It has been shown that the occurrence and development of EC is closely associated with the interaction between estrogen (estradiol, E2) and estrogen receptors (ERs), particularly ERα. As a key nuclear transcription factor, ERα is a carcinogenic factor in EC. Its interactions with upstream and downstream effectors and co-regulators have important implications for the proliferation, metastasis, invasion and inhibition of apoptosis of EC. In the present review, the structure of ERα and the regulation of ERα in multiple dimensions are described. In addition, the classical E2/ERα signaling pathway and the crosstalk between ERα and other EC regulators are elucidated, as well as the therapeutic targeting of ERα, which may provide a new direction for clinical applications of ERα in the future.

Bioevaluation of Spiro N-Propargylic β-Enaminones as Anti-Breast Cancer Agents: In Vitro and Molecular Docking Studies

The study aimed to investigate the in vitro inhibitory activities of spiro N-propargylic β-enaminones, SPEs 1-31, against BCa cells, to perform in silico molecular docking studies to understand the nature of the interaction between the compounds and the ERα, PR, EGFR, and Her2, and to determine the ADMET and drug-likeness properties. Cytotoxic activity was investigated via MTT assay. DNA fragmentation was evaluated via ELISA assay. Cell cycle distributions were investigated by flow cytometry. Expression levels of Bcl-2, Bax, p21 and Cyclin D1 were measured by qRT-PCR and western blot analysis. Molecular docking was done using Autodock/vina software. ADMET analysis was calculated using the ADMETlab 2.0 tool. SPEs 1, 22, and 28 showed selective cytotoxic activity against all BCa cells with SI values >2. SPEs induced apoptosis and caused significant changes in Bcl-2 and Bax levels. The cell cycle was arrested at the S phase and levels of p21 and Cyclin D1 were induced in all BCa cells. Molecular docking analysis revealed that SPE1, SPE22, and SPE28 showed high binding affinities with ERα, PR, EGFR, and Her2. ADMET analysis revealed that SPEs are drug-like compounds as they obey the five rules of Lipinsky and are not toxic. Therefore, these potential anticancer compounds should be further validated by in vivo studies for their appropriate function in human health with a safety profile, and a comprehensive drug interaction study should be performed.

Interplay between Estrogen, Kynurenine, and AHR Pathways: An immunosuppressive axis with therapeutic potential for breast cancer treatment

Breast cancer is one of the most common malignancies among women worldwide. Estrogen exposure via endogenous and exogenous sources during a lifetime, together with environmental exposure to estrogenic compounds, represent the most significant risk factor for breast cancer development. As breast tumors establish, multiple pathways are deregulated. Among them is the aryl hydrocarbon receptor (AHR) signaling pathway. AHR, a ligand-activated transcription factor associated with the metabolism of polycyclic aromatic hydrocarbons and estrogens, is overexpressed in breast cancer. Furthermore, AHR and estrogen receptor (ER) cross-talk pathways have been observed. Additionally, the Tryptophan (Trp) catabolizing enzymes indolamine-2,3-dioxygenase (IDO) and tryptophan-2,3-dioxygenase (TDO) are overexpressed in breast cancer. IDO/TDO catalyzes the formation of Kynurenine (KYN) and other tryptophan-derived metabolites, which are ligands of AHR. Once KYN activates AHR, it stimulates the expression of the IDO enzyme, increases the level of KYN, and activates non-canonical pathways to control inflammation and immunosuppression in breast tumors. The interplay between E2, AHR, and IDO/TDO/KYN pathways and their impact on the immune system represents an immunosuppressive axis on breast cancer. The potential modulation of the immunosuppressive E2-AHR-IDO/TDO/KYN axis has aroused great expectations in oncotherapy. The present article will review the mechanisms implicated in generating the immunosuppressive axis E2-AHR-IDO/TDO/KYN in breast cancer and the current state of knowledge as a potential therapeutic target.

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.

In-silico investigations on the anticancer activity of selected 2-aryloxazoline derivatives against breast cancer

As the in-silico study has become an important tool to search for new drugs in the concurrent era with towering acceptance and accuracy, it has been employed in our research to unearth effective cancer drugs. Breast cancer has accounted for the most serious diseases for both men and women. Although few research outputs have been obtained on breast cancer, these are not an adequate amount to ascertain new drugs. Due to this gap, virtual screening, in-silico study, and computational techniques have been used to provide the ability to design and select anticancer compounds with desirable drug-like properties of breast cancer protein, which is commonly known as fatty acid synthase. A total of nine derivatives of 2-aryloxazoline compounds were chosen, and In-silico was studied to evaluate as a potential anticancer agent with the comparison of seven Food and Drug Administration(FDA) approved breast cancer drugs. These compounds were subjected to computational studies for quantum calculations, ADME and Lipinski analysis, as well as molecular docking and MD simulations against a variety of therapeutic targets involved in cell proliferation of fatty acid synthase (PDB ID:3TJM, 3ERT, 4OAR, 2J6M). An in-silico docking study reveals that ligands Hit-4, Hit-6, and Hit-8 had the highest docking scores at -10.3 kcal/mol, -10.3 kcal/mol, and -10.2 kcal/mol towards the protein of fatty acid synthase. The ligands had docking scores better than the standard anti-breast cancer drug gefitinib (-5.3 kcal/mole). Our findings demonstrate how crucial it is for pharmaceutical researchers to develop novel drugs for the treatment of breast cancer.Communicated by Ramaswamy H. Sarma.

Icariin, a phytoestrogen, exerts rapid estrogenic actions through crosstalk of estrogen receptors in osteoblasts

Icariin, a flavonoid glycoside derived from Epimedium brevicornum Maxim, exerts bone protective effects via estrogen receptors (ERs). This study aimed to investigate the role of ER-α66, ER-α36, and GPER in bone metabolism in osteoblasts following treatment with icariin. Human osteoblastic MG-63 cells and osteoblast-specific ER-α66 knockout mice were employed. The ERs crosstalk in the estrogenic action of icariin was evaluated in ER-α66-negative human embryonic kidney HEK293 cells. Icariin, like E2, regulated ER-α36 and GPER protein expression in osteoblasts by downregulating them and upregulating ER-α66. ER-α36 and GPER suppressed the actions of icariin and E2 in bone metabolism. However, the in vivo administration of E2 (2 mg/kg/day) or icariin (300 mg/kg/day) restored bone conditions in KO osteoblasts. ER-α36 and GPER expression increased significantly and rapidly activated and translocated in KO osteoblasts after treatment with E2 or icariin. ER-α36 overexpression in KO osteoblasts further promoted the OPG/RANKL ratio induced by E2 or icariin treatment. This study showed icariin and E2 elicit rapid estrogenic responses in bone through recruiting ER-α66, ER-α36, and GPER. Notably, in osteoblasts lacking ER-α66, ER-α36, and GPER mediate the estrogenic effects of icariin and E2, while in intact osteoblasts, ER-α36 and GPER act as negative regulators of ER-α66.

A Basic Review on Estrogen Receptor Signaling Pathways in Breast Cancer

Breast cancer is the most common cancer and the deadliest among women worldwide. Estrogen signaling is closely associated with hormone-dependent breast cancer (estrogen and progesterone receptor positive), which accounts for two-thirds of tumors. Hormone therapy using antiestrogens is the gold standard, but resistance to these treatments invariably occurs through various biological mechanisms, such as changes in estrogen receptor activity, mutations in the ESR1 gene, aberrant activation of the PI3K pathway or cell cycle dysregulations. All these factors have led to the development of new therapies, such as selective estrogen receptor degraders (SERDs), or combination therapies with cyclin-dependent kinases (CDK) 4/6 or PI3K inhibitors. Therefore, understanding the estrogen pathway is essential for the treatment and new drug development of hormone-dependent cancers. This mini-review summarizes current literature on the signalization, mechanisms of action and clinical implications of estrogen receptors in breast cancer.

Loss of the receptors ER, PR and HER2 promotes USP15-dependent stabilization of PARP1 in triple-negative breast cancer

Poly(ADP-ribose) polymerase 1 (PARP1) is essential for the progression of several types of cancers. However, whether and how PARP1 is stabilized to promote genomic stability in triple-negative breast cancer (TNBC) remains unknown. Here, we demonstrated that the deubiquitinase USP15 interacts with and deubiquitinates PARP1 to promote its stability, thereby stimulating DNA repair, genomic stability and TNBC cell proliferation. Two PARP1 mutations found in individuals with breast cancer (E90K and S104R) enhanced the PARP1-USP15 interaction and suppressed PARP1 ubiquitination, thereby elevating the protein level of PARP1. Importantly, we found that estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor 2 (HER2) inhibited USP15-mediated PARP1 stabilization through different mechanisms. ER bound to the USP15 promoter to suppress its expression, PR suppressed the deubiquitinase activity of USP15, and HER2 abrogated the PARP1-USP15 interaction. The specific absence of these three receptors in TNBC results in high PARP1 levels, leading to increases in base excision repair and female TNBC cell survival.

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.

Localisation of oestrogen receptors in stem cells and in stem cell-derived neurons of the mouse

Oestrogen receptors (ER) transduce the effects of the endogenous ligand, 17β-estradiol in cells to regulate a number of important processes such as reproduction, neuroprotection, learning and memory and anxiety. The ERα or ERβ are classical intracellular nuclear hormone receptors while some of their variants or novel proteins such as the G-protein coupled receptor (GPCR), GPER1/GPR30 are reported to localise in intracellular as well as plasma membrane locations. Although the brain is an important target for oestrogen with oestrogen receptors expressed differentially in various nuclei, subcellular organisation and crosstalk between these receptors is under-explored. Using an adapted protocol that is rapid, we first generated neurons from mouse embryonic stem cells. Our immunocytochemistry approach shows that the full length ERα (ERα-66) and for the first time, that an ERα variant, ERα-36, as well as GPER1 is present in embryonic stem cells. In addition, these receptors typically decrease their nuclear localisation as neuronal maturation proceeds. Finally, although these ERs are present in many subcellular compartments such as the nucleus and plasma membrane, we show that they are specifically not colocalised with each other, suggesting that they initiate distinct signalling pathways.

Screening of Anti-carcinogenic Properties of Phytocompounds from Allium ascalonicum for Treating Breast Cancer Through In Silico and In Vitro Approaches

Plants, rich in phytocompounds, have been in usage since time immemorial for treating various diseases, namely, cancer. One such plant species, Allium ascalonicum (Shallot) belonging to Amaryllidaceae family is being studied here for its anti-carcinogenic properties against breast cancer. GC-MS characterization of A. ascalonicum exhibited 48 phytocompounds containing five peak phytocompounds and 13 phytocompounds with anti-carcinogenic properties. These 13 anti-carcinogenic phytocompounds were docked with three hormonal receptors involved in breast cancer malignancy, namely, ERα, PR, and human EGFR with tamoxifen as standard for in silico analysis. The results exhibited three phytocompounds that had better binding scores compared to that of the standard drug, tamoxifen. Lyophilized powder of aqueous A. ascalonicum extract, also referred as ASE, was used for in vitro approaches. Antioxidant study using DPPH assay revealed that the highest percentage of FRSA in ASE, nearly 51%, was observed at 50 µg/ml concentration. Cytotoxicity study on MCF-7 cell line using MTT assay demonstrated IC₅₀ value at 1400 µg/ml and anti-proliferative study using Trypan blue assay for the determination of percentage viability of MCF-7 cells at IC₅₀ concentration was observed to be 49%. Anti-mitotic activity using Vigna radiata seed germination assay revealed clear morphological differences in a dose-dependent manner between the seeds grown at various concentrations of ASE with nearly 56.5% growth inhibition observed at 1500 µg/ml concentration. Hence, this research work proves that Allium ascalonicum has very good anti-carcinogenic properties and this can be confirmed further through in vivo animal model studies and it can also be formulated as a promising drug to treat breast cancer. GC-MS characterization of Allium ascalonicum demonstrated the presence of five peak compounds and thirteen anti-carcinogenic compounds. The thirteen anti-carcinogenic compounds were docked with three target proteins (in silico analysis) involved in breast cancer malignancy and identified the presence of three potential phytocompounds that can be used for treating breast cancer. In vitro approaches also confirmed the presence of anti-carcinogenic properties such as antioxidative potential, cytotoxic, anti-proliferative, and anti-mitotic effects. Hence, Allium ascalonicum can be taken further to in vivo studies so that it can be formulated to treat breast cancer.

Estrogen Receptor Signaling in the Immune System

The immune system functions in a sexually dimorphic manner, with females exhibiting more robust immune responses than males. However, how female sex hormones affect immune function in normal homeostasis and in autoimmunity is poorly understood. In this review, we discuss how estrogens affect innate and adaptive immune cell activity and how dysregulation of estrogen signaling underlies the pathobiology of some autoimmune diseases and cancers. The potential roles of the major circulating estrogens, and each of the 3 estrogen receptors (ERα, ERβ, and G-protein coupled receptor) in the regulation of the activity of different immune cells are considered. This provides the framework for a discussion of the impact of ER modulators (aromatase inhibitors, selective estrogen receptor modulators, and selective estrogen receptor downregulators) on immunity. Synthesis of this information is timely given the considerable interest of late in defining the mechanistic basis of sex-biased responses/outcomes in patients with different cancers treated with immune checkpoint blockade. It will also be instructive with respect to the further development of ER modulators that modulate immunity in a therapeutically useful manner.

Metabolomic and Transcriptomic Changes Underlying the Effects of L-Citrulline Supplementation on Ram Semen Quality

This study examined the effects of L-Cit supplementation on ram semen quality through metabolomics and transcriptomics. A total of 16 rams were randomly categorized into two groups. The control group was fed a basic diet, whereas the experimental group received feed supplemented with 12 g/d of L-Cit. Semen and blood were collected from the rams on days 0 and 72 to measure sugar, pyruvate, amino acid, and nontargeted metabolite contents. Additionally, hypothalamic and testicular tissues were collected for a transcriptomic analysis. We found 27 differential metabolites between the control and experimental groups, of which 21 were downregulated (p < 0.05) and 6 were upregulated (p < 0.05). Compared with the control group, xylose and pyruvate contents in seminal plasma increased by 43.86% and 162.71%, respectively (p < 0.01). Additionally, the levels of 11 amino acids showed a significant increase in seminal plasma (p < 0.01). Furthermore, 961 and 715 differentially expressed genes were detected in the hypothalamic and testicular tissues, respectively. The pathways of significant enrichment in the hypothalamus and testes were protein digestion, absorption, glycolysis/gluconeogenesis, and amino as well as nucleotide sugar metabolisms. In the present study, L-Cit improved protein synthesis and blood metabolism, consequently increasing the contents of most amino acids in ram seminal plasma. Specifically, the hypothalamus controlled the expression of glycolysis/gluconeogenesis-related genes in the testes through its metabolites released into the serum, thereby providing energy for sperm production, which led to a decrease in the sugar content of seminal plasma.

Metabolomic and Transcriptomic Changes Underlying the Effects of L-Citrulline Supplementation on Ram Semen Quality

This study examined the effects of L-Cit supplementation on ram semen quality through metabolomics and transcriptomics. A total of 16 rams were randomly categorized into two groups. The control group was fed a basic diet, whereas the experimental group received feed supplemented with 12 g/d of L-Cit. Semen and blood were collected from the rams on days 0 and 72 to measure sugar, pyruvate, amino acid, and nontargeted metabolite contents. Additionally, hypothalamic and testicular tissues were collected for a transcriptomic analysis. We found 27 differential metabolites between the control and experimental groups, of which 21 were downregulated (p < 0.05) and 6 were upregulated (p < 0.05). Compared with the control group, xylose and pyruvate contents in seminal plasma increased by 43.86% and 162.71%, respectively (p < 0.01). Additionally, the levels of 11 amino acids showed a significant increase in seminal plasma (p < 0.01). Furthermore, 961 and 715 differentially expressed genes were detected in the hypothalamic and testicular tissues, respectively. The pathways of significant enrichment in the hypothalamus and testes were protein digestion, absorption, glycolysis/gluconeogenesis, and amino as well as nucleotide sugar metabolisms. In the present study, L-Cit improved protein synthesis and blood metabolism, consequently increasing the contents of most amino acids in ram seminal plasma. Specifically, the hypothalamus controlled the expression of glycolysis/gluconeogenesis-related genes in the testes through its metabolites released into the serum, thereby providing energy for sperm production, which led to a decrease in the sugar content of seminal plasma.

Targeting hormone-resistant breast cancer cells with docetaxel: a look inside the resistance

Aim: The study aims to analyze the effect of long-term incubation of ERα-positive MCF7 breast cancer cells with 4-hydroxytamoxifen (HT) on their sensitivity to tubulin polymerization inhibitor docetaxel. Methods: The analysis of cell viability was performed by the MTT method. The expression of signaling proteins was analyzed by immunoblotting and flow cytometry. ERα activity was evaluated by gene reporter assay. To establish hormone-resistant subline MCF7, breast cancer cells were treated with 4-hydroxytamoxifen for 12 months. Results: The developed MCF7/HT subline has lost sensitivity to 4-hydroxytamoxifen, and the resistance index was 2. Increased Akt activity (2.2-fold) and decreased ERα expression (1.5-fold) were revealed in MCF7/HT cells. The activity of the estrogen receptor α was reduced (1.5-fold) in MCF7/HT. Evaluation of class III β-tubulin expression (TUBB3), a marker associated with metastasis, revealed the following trends: higher expression of TUBB3 was detected in triple-negative breast cancer MDA-MB-231 cells compared to hormone-responsive MCF7 cells (P < 0.05). The lowest expression of TUBB3 was found in hormone-resistant MCF7/HT cells (MCF7/HT < MCF7 < MDA-MB-231, approximately 1:2:4). High TUBB3 expression strongly correlated with docetaxel resistance: IC₅₀ value of docetaxel for MDA-MB-231 cells was greater than that for MCF7 cells, whereas resistant MCF7/HT cells were the most sensitive to the drug. The accumulation of cleaved PARP (a 1.6-fold increase) and Bcl-2 downregulation (1.8-fold) were more pronounced in docetaxel-treated resistant cells (P < 0.05). The expression of cyclin D1 decreased (2.8-fold) only in resistant cells after 4 nM docetaxel treatment, while this marker was unchanged in parental MCF7 breast cancer cells. Conclusion: Further development of taxane-based chemotherapy for hormone-resistant cancer looks highly promising, especially for cancers with low TUBB3 expression.

ESR1 activating mutations: From structure to clinical application

Estrogen receptor-positive breast cancer is the most common type of both early and advanced breast cancer. Estrogen receptor alpha (ER) is a nuclear hormone receptor and a key driver of tumorigenesis and tumor progression in these breast cancers. As such, it is a key treatment target and a biomarker predictive of response to endocrine therapy. Activating ESR1 ligand binding domain mutations engender constitutive/ligand independent transcriptional activities and emerge following prolonged first-line hormone therapy regimens, mainly from aromatase inhibitors. The full scale of the biological and clinical significance of these mutations continue to evolve and additional studies are required to further discern the multimodal effects of these mutations on ER transcription, metastatic propensity, and the tumor microenvironment. Furthermore, recent and ongoing studies highlight the potential clinical utility of these mutations as therapeutic targets and dynamic biomarkers. Herein, we review the structure, functional consequences, and clinical implications of the activating ESR1 mutations in advanced estrogen receptor-positive breast cancer.

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.

14-3-3τ drives estrogen receptor loss via ERα36 induction and GATA3 inhibition in breast cancer

About one-fourth of recurrent estrogen receptor-positive (ER+) breast cancers lose ER expression, leading to endocrine therapy failure. However, the mechanisms underlying ER loss remain to be fully explored. We now show that 14-3-3τ, up-regulated in ∼60% of breast cancer, drives the conversion of ER+ to ER- and epithelial-to-mesenchymal transition (EMT). We identify ERα36, an isoform of ERα66, as a downstream effector of 14-3-3τ. Overexpression of 14-3-3τ induces ERα36 in xenografts and tumor spheroids. The regulation is further supported by a positive correlation between ERα36 and 14-3-3τ expression in human breast cancers. ERα36 can antagonize ERα66 and inhibit ERα66 expression. Isoform-specific depletion of ERα36 blocks the ER conversion and EMT induced by 14-3-3τ overexpression in tumor spheroids, thus establishing ERα36 as a key mediator in 14-3-3τ-driven ER loss and EMT. ERα36 promoter is repressed by GATA3, which can be phosphorylated by AKT at consensus binding sites for 14-3-3. Upon AKT activation, 14-3-3τ binds phosphorylated GATA3 and facilitates the degradation of GATA3 causing GATA3 to lose transcriptional control over its target genes ERα66 and ERα36. We also demonstrate a role for the collaboration between 14-3-3τ and AKT in ERα36 induction and endocrine therapy resistance by three-dimensional spheroid and tamoxifen treatment models in MCF7 and T47D ER+ breast cancer cells. Thus, the 14-3-3τ-ERα36 regulation provides a previously unrecognized mechanism for ER loss and endocrine therapy failure.

Study on the prognosis, immune and drug resistance of m6A-related genes in lung cancer

Background

Few studies have demonstrated that the relationship between m6A-related genes and the prognosis, tumor microenvironment and drug resistance of LC.

Methods

The main results were analyzed with bioinformatics methods.

Results

Hence, we found 10 m6A-related genes expressed less in tumor samples in comparison with normal ones. Using consensus clustering, all LC patients were grouped into 2 subgroups according to the overall expression of 10 differential expressed m6A-related genes. In two clusters, the OS and immune characteristics were different. We analyzed the predictive potential of 10 m6A-related genes in the prognosis of LC, and obtained a risk prognosis model on the strength of ZC3H13, CBLL1, ELAVL1 and YTHDF1 as the hub candidate genes through LASSO cox. The expression of 4 hub m6A-related genes was validated by IHC in the HPA database. The infiltration level of dendritic cell, CD4+ T cell and neutrophil that were affected by CNV level of m6A-related genes in LUAD and LUSC patients. Moreover, based on GSCALite database, we found that LUSC patients with hypermethylation tended to have a better overall survival. In terms of drug sensitivity, etoposide correlated negatively with ELAVL1, HNRNPC, RBM15B, YTHDF2 and CBLL1. ZC3H13 had positively association with afatinib, while HNRNPC was positively associated with dasatinib, erlotinib, lapatinib and TGX221. Crizotinib had a negative correlation with ELAVL1, CBLL1, HNRNPC and RBM15B.

Conclusion

In conclusion, m6A-related genes are important participants in LC and the expression levels of ZC3H13, CBLL1, ELAVL1 and YTHDF1 are significant for prediction and treatment of LC. Researches of drug resistance based on m6A-related genes need to pay more attention for producing new therapeutic strategies of LC and CBLL1 may contribute to target treatment for further research.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12859-022-04984-5.

High GPER expression in triple-negative breast cancer is linked to pro-metastatic pathways and predicts poor patient outcomes

Triple-negative breast cancer (TNBC) is a particularly aggressive and heterogeneous disease with few effective targeted therapies and precision therapeutic options over a long period. It is generally considered that TNBC is an estrogen-independent breast cancer, while a new estrogen receptor, namely G protein-coupled estrogen receptor (GPER), is demonstrated to mediate estrogenic actions in TNBC. Based on our transcriptomic analysis, expression of GPER was correlated with clinicopathological variables and survival of 360 TNBC patients. GPER expression at mRNA level was significantly correlated with immunohistochemistry scoring in 12 randomly chosen samples. According to the cutoff value, 26.4% (95/360) of patients showed high GPER expression and significant correlation with the mRNA subtype of TNBC (P = 0.001), total metastatic events (P = 0.019) and liver metastasis (P = 0.011). In quantitative comparison, GPER abundance is correlated with the high-risk subtype of TNBC. At a median follow-up interval of 67.1 months, a significant trend towards reduced distant metastasis-free survival (DMFS) (P = 0.014) was found by Kaplan–Meier analysis in patients with high GPER expression. Furthermore, univariate analysis confirmed that GPER was a significant prognostic factor for DMFS in TNBC patients. Besides, high GPER expression was significantly linked to the worse survival in patients with lymph node metastasis, TNM stage III as well as nuclear grade G3 tumors. Transcriptome-based bioinformatics analysis revealed that GPER was linked to pro-metastatic pathways in our cohort. These results may supply new insights into GPER-mediated estrogen carcinogenesis in TNBC, thus providing a potential strategy for endocrine therapy of TNBC.

Estrogen receptor variant ER-α36 facilitates estrogen signaling via EGFR in glioblastoma

Glioblastoma (GBM) is a deadly and common primary brain tumor. Poor prognosis is linked to high proliferation and cell heterogeneity. Sex differences may play a role in patient outcome. Previous studies showed that ER-α36, a variant of the estrogen receptor (ER), mediated non-genomic estrogen signaling and is highly expressed in many ER-negative malignant tumors. ER-α36 also associates with epidermal growth factor receptor (EGFR). The primary purpose of this study is to investigate the cross talk between ER-α36 and EGFR in estrogen-mediated GBM cell proliferation. Here, we showed that ER-α36 was highly expressed and confirmed that ER-α36 co-labels with EGFR in human GBM samples using immunohistochemical techniques. We also investigated the mechanisms of estrogen-induced proliferation in ER-α-negative cell lines. We found that GBM cells showed varying responsive to mitogenic estrogen signaling which correlated with ER-α36 expression, and knockdown of ER-α36 diminished the response. Exposure to estrogen also caused upregulation of cyclin protein expression in vitro. We also found that low concentration of estrogen promoted SRC-Y-416 and inhibited SRC-Y-527 phosphorylation, corresponding with activated SRC signaling. Inhibiting SRC or EGFR abolished estrogen-induced mitogenic signaling, including cyclin expression and MAPK phosphorylation. Cumulatively, our results demonstrate that ER-α36 promotes non-genomic estrogen signaling via the EGFR/SRC/MAPK pathway in GBM. This may be important for the treatment of ER-α-negative GBMs that retain high level of ER-α36, since estrogen may be a viable therapeutic target for these patients.

Vitamin D, Th17 Lymphocytes, and Breast Cancer

Simple Summary

The effect of vitamin D₃ on the development of breast cancer (favorable, ineffective, or even unfavorable) depends on many factors, such as age, menopausal status, or obesity. The immunomodulatory effect of vitamin D may be unfavorable in case of breast cancer progression. The effect of vitamin D on Th17 cells may depend on disease type and patients’ age. Our goal was to summarize the data available and to find indications of vitamin D treatment failure or success. Therefore, in this review, we present data describing the effects of vitamin D₃ on Th17 cells, mainly in breast cancer.

Abstract

Vitamin D₃, which is well known to maintain calcium homeostasis, plays an important role in various cellular processes. It regulates the proliferation and differentiation of several normal cells, including immune and neoplastic cells, influences the cell cycle, and stimulates cell maturation and apoptosis through a mechanism dependent on the vitamin D receptor. The involvement of vitamin D₃ in breast cancer development has been observed in numerous clinical studies. However, not all studies support the protective effect of vitamin D₃ against the development of this condition. Furthermore, animal studies have revealed that calcitriol or its analogs may stimulate tumor growth or metastasis in some breast cancer models. It has been postulated that the effect of vitamin D₃ on T helper (Th) 17 lymphocytes is one of the mechanisms promoting metastasis in these murine models. Herein we present a literature review on the existing data according to the interplay between vitamin D, Th17 cell and breast cancer. We also discuss the effects of this vitamin on Th17 lymphocytes in various disease entities known to date, due to the scarcity of scientific data on Th17 lymphocytes and breast cancer. The presented data indicate that the effect of vitamin D₃ on breast cancer development depends on many factors, such as age, menopausal status, or obesity. According to that, more extensive clinical trials and studies are needed to assess the importance of vitamin D in breast cancer, especially when no correlations seem to be obvious.

Rewiring of the Endocrine Network in Triple-Negative Breast Cancer

The immunohistochemical definition of estrogen/progesterone receptors dictates endocrine feasibility in the treatment course of breast cancer. Characterized by the deficiency of estrogen receptor α, ERα-negative breast cancers are dissociated from any endocrine regimens in the routine clinical setting, triple-negative breast cancer in particular. However, the stereotype was challenged by triple-negative breast cancers’ retained sensitivity and vulnerability to endocrine agents. The interplay of hormone action and the carcinogenic signaling program previously underscored was gradually recognized along with the increasing investigation. In parallel, the overlooked endocrine-responsiveness in ERα-negative breast cancers attracted attention and supplied fresh insight into the therapeutic strategy in an ERα-independent manner. This review elaborates on the genomic and non-genomic steroid hormone actions and endocrine-related signals in triple-negative breast cancers attached to the hormone insensitivity label. We also shed light on the non-canonical mechanism detected in common hormone agents to showcase their pleiotropic effects.

Downregulation of estrogen receptor-α36 expression attenuates metastasis of hepatocellular carcinoma cells

This study aimed to examine the role of estrogen receptor (ER)-α36 in the metastasis of hepatocellular carcinoma (HCC) and in the epithelial-mesenchymal transition (EMT). HCC HepG2 and Huh7 cells with the knocked-down level of ER-α36 expression were established. Cell growth and migration of the HepG2 and Huh7 cell variants were studied using MTS, transwell, and wound-healing assays, and the metastatic abilities of HepG2 cell variants were examined using a tail-vein injection model in nude mice. Levels of EMT markers, Src phosphorylation in HepG2 and Huh7 cell variants, and tumors formed by HepG2 cell variants in the nude mice were examined using Western blot and immunohistochemistry. We found that the growth and metastatic abilities of HepG2 and Huh7 cells with the knocked-down level of ER-α36 expression (HepG2/Si36 and Huh7/Si36) were significantly reduced, with increased levels of cytokeratin and E-Cadherin expression, and decreased levels of Vimentin, Snail, Slug and the Src phosphorylation, compared to the HCC cells transfected with an empty vector (HepG2/Vector and Huh7/Vector). We also found ER-α36 knockdown suppressed the lung metastasis of HepG2 cells with the involvement of EMT and the Src pathway in vivo. The Src inhibitor PP2 suppressed the growth and migration of HepG2/Vector and Huh7/Vector cells with decreased Vimentin, Snail, and Slug and increased cytokeratin and E-Cadherin expressions, but failed to induce the migration and the EMT markers in HepG2/Si36 and Huh7/Si36 cells. ER-α36 is involved in the metastasis of HCC cells through the regulation of EMT and the Src signaling pathway.

DLGAP1-AS2 promotes estrogen receptor signalling and confers tamoxifen resistance in breast cancer

BACKGROUND

Tamoxifen is a first-line endocrine agent and is often used to treat estrogen receptor-positive (ER+) breast cancer. Unfortunately, approximately 30-40% of patients who received tamoxifen therapy experience recurrence or progression to a fatal advanced stage due to tamoxifen resistance. However, the mechanisms of tamoxifen resistance remain unclear.

METHODS

The expression of lncRNA DLGAP1 antisense RNA 2 (DLGAP1-AS2) was detected by qPCR. The effect of DLGAP1-AS2 on tamoxifen resistance was evaluated by MTT, colony formation, TUNEL and flow cytometric assays. The mechanisms by which DLGAP1-AS2 regulates tamoxifen resistance were investigated through qPCR, RNA pull-down assays and RNA immunoprecipitation (RIP) assays.

RESULTS

Our results showed that DLGAP1-AS2 is significantly upregulated in breast cancer and that tamoxifen can induce DLGAP1-AS2 expression. Further investigation suggested that upregulation of DLGAP1-AS2 can increase cell viability and inhibit apoptosis, while downregulation of DLGAP1-AS2 results in the opposite effects. Mechanistically, DLGAP1-AS2 can bind to the AFF3 protein to inhibit its degradation, which further promotes ER signalling.

CONCLUSIONS

Our research clarified that DLGAP1-AS2 promotes ER signalling to induce tamoxifen resistance and that targeting DLGAP1-AS2 might be a promising strategy to overcome tamoxifen resistance in breast cancer.

ERα36-High Cancer-Associated Fibroblasts as an Unfavorable Factor in Triple-Negative Breast Cancer

Background: Cancer-associated fibroblasts (CAFs) are the most abundant cell type in the tumor microenvironment (TME). Estrogen receptor alpha 36 (ERα36), the alternatively spliced variant of ERα, is described as an unfavorable factor when expressed in cancer cells. ERα can be expressed also in CAFs; however, the role of ERα36 in CAFs is unknown. Methods: Four CAF cultures were isolated from chemotherapy-naïve BC patients and characterized for ERα36 expression and the NanoString gene expression panel using isolated RNA. Conditioned media from CAF cultures were used to assess the influence of CAFs on triple-negative breast cancer (TNBC) cells using a matrigel 3D culture assay. Results: We found that ERα36high CAFs significantly induced the branching of TNBC cells in vitro (p < 0.001). They also produced a set of pro-tumorigenic cytokines compared to ERα36low CAFs, among which hepatocyte growth factor (HGF) was the main inducer of TNBC cell invasive phenotype in vitro (p < 0.001). Tumor stroma rich in ERα36high CAFs was correlated with high Ki67 expression (p = 0.041) and tumor-associated macrophages markers (CD68 and CD163, p = 0.041 for both). HGF was found to be an unfavorable prognostic factor in TCGA database analysis (p = 0.03 for DFS and p = 0.04 for OS). Conclusions: Breast cancer-associated fibroblasts represent distinct subtypes based on ERα36 expression. We propose that ERα36high CAFs could account for an unfavorable prognosis for TNBC patients.

Low concentrations of 17β-estradiol exacerbate tamoxifen resistance in breast cancer treatment through membrane estrogen receptor-mediated signaling pathways

The present study aims to discover the influences of tamoxifen and 17β-estradiol (E2) on tamoxifen-resistant (TamR) patients in vitro. Herein, we established a stabilized TamR MCF-7 cell line at 1 μM via gradient concentrations of tamoxifen cultivation. The expression changes of four ER subtypes (ERα66, ERβ, ERα36 and GPR30) were found to bring about tamoxifen resistance. Moreover, the generation of tamoxifen resistance involved in apoptosis escape via a reactive oxygen species-regulated p53 signaling pathway. Interestingly, E2 at environmental concentrations (0.1-10 nM) could activate the expression of both ERα36 and GPR30, and then stimulate the phosphorylation of ERK1/2 and Akt, resulting in cell growth promotion. Cell migration and invasion promotion, apoptosis inhibition, and cell cycle G1-S progression are involved in such proliferative effects. Conversely, the application of specific antagonists of ERα36 and GPR30 could restore tamoxifen's sensitivity as well as partially offset E2-mediated proliferation. In short, overexpression of ERα36 and GPR30 not only ablate tamoxifen responsiveness but also could promote tumor progression of TamR breast cancer under estrogen conditions. These results provided novel insights into underlying mechanisms of tamoxifen resistance and the negative effects of steroid estrogens at environmental concentrations on TamR MCF-7 cells, thus generating new thoughts for future management of ER-positive breast cancer.

Estrogen receptor-α36 is involved in diallyl sulfide-induced inhibition of malignant growth of HepG2 and Huh7 hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) is a highly malignant disease that currently lacks effective treatment. Epidemiological studies have suggested the preventive role of raw garlic intake in different tumors, such as HCC. Although diallyl sulfide (DAS), the main component of garlic extracts, has been reported to inhibit the growth of HCC cells, the underlying mechanism remains elusive. This study aimed to investigate the inhibitory effect of DAS on the growth of HepG2 and Huh7 hepatocellular carcinoma cells and its underlying mechanism. HepG2 and Huh7 cells were treated with DAS and nude mice were intrahepatically injected with human HCC HepG2 cells and maintained with or without DAS administration for 28 days. MTS and clonogenic assays revealed that DAS inhibited the growth and clonogenicity of HepG2 and Huh7 hepatocellular carcinoma cells. Furthermore, DAS inhibited the growth of xenograft tumors accompanied by a decreased rate of pathological karyomitosis as observed by H&E staining. The expression levels of estrogen receptor-α36 (ER-α36) and epidermal growth factor receptor (EGFR) in HepG2 and Huh7 cells and in xenograft tumors derived from HepG2 cells after DAS treatment were detected by immunohistochemistry and western blotting. We found that DAS disrupted the positive regulatory loop between ER-α36 and EGFR, and decreased the phosphorylation of AKT at Ser 473 both in vivo and in vitro. DAS also induced cell apoptosis, as evidenced by Hoechst and TUNEL staining. Western blotting revealed activation of caspase3, increased BAX and decreased Bcl-2 expression. However, the ER-α36 expression knockdown attenuated DAS-induced ERK and AKT phosphorylation in HCC cells. DAS was also able to inhibit ER-α36-mediated activation of the MAPK/ERK signaling induced by estrogen. Thus, our results indicate that ER-α36 signaling is involved in DAS-induced inhibition of HCC cell growth both in vitro and in vivo.

Estrogen Receptors-Mediated Apoptosis in Hormone-Dependent Cancers

It is known that estrogen stimulates growth and inhibits apoptosis through estrogen receptor(ER)-mediated mechanisms in many cancer cell types. Interestingly, there is strong evidence that estrogens can also induce apoptosis, activating different ER isoforms in cancer cells. It has been observed that E2/ERα complex activates multiple pathways involved in both cell cycle progression and apoptotic cascade prevention, while E2/ERβ complex in many cases directs the cells to apoptosis. However, the exact mechanism of estrogen-induced tumor regression is not completely known. Nevertheless, ERs expression levels of specific splice variants and their cellular localization differentially affect outcome of estrogen-dependent tumors. The goal of this review is to provide a general overview of current knowledge on ERs-mediated apoptosis that occurs in main hormone dependent-cancers. Understanding the molecular mechanisms underlying the induction of ER-mediated cell death will be useful for the development of specific ligands capable of triggering apoptosis to counteract estrogen-dependent tumor growth.

Estradiol Signaling at the Heart of Folliculogenesis: Its Potential Deregulation in Human Ovarian Pathologies

Estradiol (E2) is a major hormone controlling women fertility, in particular folliculogenesis. This steroid, which is locally produced by granulosa cells (GC) within ovarian follicles, controls the development and selection of dominant preovulatory follicles. E2 effects rely on a complex set of nuclear and extra-nuclear signal transduction pathways principally triggered by its nuclear receptors, ERα and ERβ. These transcription factors are differentially expressed within follicles, with ERβ being the predominant ER in GC. Several ERβ splice isoforms have been identified and display specific structural features, which greatly complicates the nature of ERβ-mediated E2 signaling. This review aims at providing a concise overview of the main actions of E2 during follicular growth, maturation, and selection in human. It also describes the current understanding of the various roles of ERβ splice isoforms, especially their influence on cell fate. We finally discuss how E2 signaling deregulation could participate in two ovarian pathogeneses characterized by either a follicular arrest, as in polycystic ovary syndrome, or an excess of GC survival and proliferation, leading to granulosa cell tumors. This review emphasizes the need for further research to better understand the molecular basis of E2 signaling throughout folliculogenesis and to improve the efficiency of ovarian-related disease therapies.

Segregation of nuclear and membrane-initiated actions of estrogen receptor using genetically modified animals and pharmacological tools

Estrogen receptor alpha (ERα) and beta (ERβ) are members of the nuclear receptor superfamily, playing widespread functions in reproductive and non-reproductive tissues. Beside the canonical function of ERs as nuclear receptors, in this review, we summarize our current understanding of extra-nuclear, membrane-initiated functions of ERs with a specific focus on ERα. Over the last decade, in vivo evidence has accumulated to demonstrate the physiological relevance of this ERα membrane-initiated-signaling from mouse models to selective pharmacological tools. Finally, we discuss the perspectives and future challenges opened by the integration of extra-nuclear ERα signaling in physiology and pathology of estrogens.

In silico molecular docking and dynamic simulation of eugenol compounds against breast cancer

Breast cancer is one of the most severe problems, and it is the primary cause of cancer-related death in females worldwide. The adverse effects and therapeutic resistance development are among the most potent clinical issues for potent medications for breast cancer treatment. The eugenol molecules have a significant affinity for breast cancer receptors. The aim of the study has been on the eugenol compounds, which has potent actions on Erα, PR, EGFR, CDK2, mTOR, ERBB2, c-Src, HSP90, and chemokines receptors inhibition. Initially, the drug-likeness property was examined to evaluate the anti-breast cancer activity by applying Lipinski's rule of five on 120 eugenol molecules. Further, structure-based virtual screening was performed via molecular docking, as protein-like interactions play a vital role in drug development. The 3D structure of the receptors has been acquired from the protein data bank and is docked with 87 3D PubChem and ZINC structures of eugenol compounds, and five FDA-approved anti-cancer drugs using AutoDock Vina. Then, the compounds were subjected to three replica molecular dynamic simulations run of 100 ns per system. The results were evaluated using root mean square deviation (RMSD), root mean square fluctuation (RMSF), and protein-ligand interactions to indicate protein-ligand complex stability. The results confirm that Eugenol cinnamaldehyde has the best docking score for breast cancer, followed by Aspirin eugenol ester and 4-Allyl-2-methoxyphenyl cinnamate. From the results obtained from in silico studies, we propose that the selected eugenols can be further investigated and evaluated for further lead optimization and drug development.

ERa-36 instead of ERa mediates the stimulatory effects of estrogen on the expression of viral oncogenes HPV E6/E7 and the malignant phenotypes in cervical cancer cells

High risk human papillomavirus (HPV) is the main causative factor of cervical cancer. In addition, estrogen and its receptors are also involved in the development of carcinogenesis. The canonical estrogen receptor ERα is frequently deficient while its variant ERα-36 is highly expressed in cervical cancer cells. The biological significance for this receptor transition from ERα to ERα-36 remains unclear. In the present study, the results of RT-PCR and Western blot demonstrated that ERα and ERα-36 function antagonistically on the expression of the viral oncogenes HPV E6 and E7. At mRNA and protein levels, ERα inhibited HPV E6/E7 expression whereas ERα-36 stimulated HPV E6/E7 expression. Overexpression of ERα-36 promoted cell proliferation while reintroduction of ERα into cervical cancer cells did not significantly affect cell proliferation which is in line with the different effects of . ERα-36 and ERα on the expression of cell cycle regulator, namely p53, p21 and cyclin D1. Furthermore, ERα suppressed whereas ERα-36 promoted the migration and invasion of cervical cancer cells, which should be related to the oppositive roles of ERα and ERα-36 in the Wnt/β-catenin/MRTF-A signaling pathway which is activated by HPV E7. Results of this study suggest that ERα functions as a tumor suppressor whereas ERα-36 is an oncoprotein in cervical cancer cells. ERα deficiency together with ERα-36 overexpression might enhance the expression of HPV E6/E7 genes and facilitate the development of cervical cancer. Targeting ERα-36 with selective antagonists should be a promising strategy for cervical cancer therapy.

Ischemic heart disease and cardioprotection: Focus on estrogenic hormonal setting and microvascular health

Ischemic Heart Disease (IHD) is a clinical condition characterized by insufficient blood flow to the cardiac tissue, and the consequent inappropriate oxygen and nutrients supply and metabolic waste removal in the heart. In the last decade a broad scientific literature has underlined the distinct mechanism of onset and the peculiar progress of IHD between female and male patients, highlighting the estrogenic hormonal setting as a key factor of these sex-dependent divergences. In particular, estrogen-activated cardioprotective pathways exert a pivotal role for the microvascular health, and their impairment, both physiologically and pathologically driven, predispose to vascular dysfunctions. Aim of this review is to summarize the current knowledge on the estrogen receptors localization and function in the cardiovascular system, particularly focusing on sex-dependent differences in microvascular vs macrovascular dysfunction and on the experimental models that allowed the researchers to reach the current findings and sketching the leading estrogen-mediated cardioprotective mechanisms.

From Micro to Long: Non-Coding RNAs in Tamoxifen Resistance of Breast Cancer Cells

Breast cancer is the most commonly diagnosed cancer and the leading cause of cancer mortality among women. Two thirds of patients are classified as hormone receptor positive, based on expression of estrogen receptor alpha (ERα), the main driver of breast cancer cell proliferation, and/or progesterone receptor, which is regulated by ERα. Despite presenting the best prognosis, these tumors can recur when patients acquire resistance to treatment by aromatase inhibitors or antiestrogen such as tamoxifen (Tam). The mechanisms that are involved in Tam resistance are complex and involve multiple signaling pathways. Recently, roles for microRNAs and lncRNAs in controlling ER expression and/or tamoxifen action have been described, but the underlying mechanisms are still little explored. In this review, we will discuss the current state of knowledge on the roles of microRNAs and lncRNAs in the main mechanisms of tamoxifen resistance in hormone receptor positive breast cancer. In the future, this knowledge can be used to identify patients at a greater risk of relapse due to the expression patterns of ncRNAs that impact response to Tam, in order to guide their treatment more efficiently and possibly to design therapeutic strategies to bypass mechanisms of resistance.

ER-α36 Promotes the Malignant Progression of Cervical Cancer Mediated by Estrogen via HMGA2

Objectives

Estrogen is proven to promote the malignant behaviors of many cancers via its receptors. Estrogen receptor alfa 36 (ER-α36) is a newly identified isoform of estrogen receptor alfa (ER-α), the role of ER-α36 in regulating the effects of estrogen and its potential impact on human cervical cancer is poorly understood.

Methods

Immunohistochemistry staining was used to evaluate the expression of ER-α36, estrogen receptor alfa 66 (ER-α66) and their prognostic values in cervical cancer. The effects of ER-α36 and ER-α66 on the proliferation and metastasis of cervical cancer were measured in vitro. A xenograft tumor assay was used to study the tumorigenesis role of ER-α36 in vivo. Furthermore, the functional gene at the downstream of ER-α36 was obtained via next-generation sequencing, and the biological functions of high mobility group A2 (HMGA2) in cervical cancer cells were investigated in vitro.

Results

ER-α36 was over-expressed in cervical cancer tissues and elevated ER-α36 expression was associated with poor prognosis in cervical cancer patients. High expression of ER-α36 promoted the proliferation, invasion and metastasis of cervical cancer cells mediated by estrogen, while silencing ER-α36 had the opposite effects. Further research showed that HMGA2 was a downstream target of ER-α36 in cervical cancer cells. The oncogenic effect of ER-α36 was attenuated after HMGA2 knockdown.

Conclusions

High expression of ER-α36 was correlated with a poor prognosis in cervical cancer by regulating HMGA2. ER-α36 could be a prognostic biomarker and a target for cervical cancer treatment.

Association of ERα-36 expression with the de novo resistance of tamoxifen in ER-positive breast cancer

BACKGROUND

Approximately 70-80% of breast cancer express ER-alpha and hormonal therapies, given significant improvements in patient survival. About 50% of ER-positive breast cancer patients with advanced disease insensitive to tamoxifen treatment when diagnosed. Recent studies have shown that ERα-36 is a crucial factor in the resistance of tamoxifen.

OBJECTIVE

This study aims to determine the association between ERα-36 expression and de novo resistance of tamoxifen in patients with ER-positive breast cancer.

METHODS

This study was an observational study using a cross-sectional method and was conducted at Wahidin Sudirohusodo Hospital and Unhas Hospital. ERα-36 protein expression was assessed using an immunohistochemistry assay. The association of ERα-36 expression and resistance of tamoxifen was tested with the Chi-square test.

RESULTS

A total of 50 locally advanced breast cancer cases were included in this study, 22 cases (44%) had overexpression of ERα-36, and 28 cases (56%) had not, 24 cases (48%) had experience resistance to tamoxifen and 26 cases (52%) had not. There was a significant association between ERα-36 expressions and resistance of tamoxifen (p = 0.000).

CONCLUSIONS

There was an association between the expression of ER-α36 with de novo resistance of tamoxifen in ER-positive breast cancer. ER-α36 could act as a worth considering biomarker for de novo resistance of tamoxifen in therapeutic strategies.

MicroRNAs expression analysis shows key affirmation of Synaptopodin-2 as a novel prognostic and therapeutic biomarker for colorectal and cervical cancers

MicroRNAs play a crucial role in tumorigenesis, tumor progression, and metastasis, and thus they contribute in development of different malignancies including cervical cancer (CC) and colorectal cancer (CRC). Through integrated strategies of computational biology, this study aims to identify prognostic biomarkers responsible for CRC and CC prognosis, and potential therapeutic agents to halt the progression of these cancers. Expression analysis of miRNA datasets of CRC and CC identified 17 differentially expressed miRNAs (DEMs). SYNPO2, NEGR1, FGF7, LIFR, RUNX1T1, CFL2, BNC2, EPHB2, PMAIP1, and CDC25A differentially expressed genes (DEGs) regulated by these DEMs were classified as candidate genes responsible for CRC and CC. Down-regulation of Synaptopodin-2 (SYNPO2) is involved in emergence and progression of these cancers by activating ER, PI3K/AKT, and EMT pathways as well as by suppressing DNA damage response, and cell cycle pathways. Higher methylation rate in promoter region of SYNPO2 could be a possible reason for lowering the expression of SYNPO2 in tumor stages. Hence, the lower expression of SYNPO2 is associated with poor prognosis of CRC and CC and could function as prognostic biomarker and therapeutic target. Fourteen transcription factors were recognized which can activate/inhibit the transcription of SYNPO2 and may be a potential target to regulate expression of SYNPO2 in CRC and CC. Retinoic acid and Estradiol were identified as putative therapeutic drugs for CRC and CC patients. This study will thus help in understanding the underlying molecular events in CRC and CC that may improve the detection of malignant lesions in primary screening and will broaden the clinical applications.

CUL4B renders breast cancer cells tamoxifen-resistant via miR-32-5p/ER-α36 axis

Tamoxifen (TAM) resistance is a significant clinical challenge in endocrine therapies for estrogen receptor (ER)-positive breast cancer patients. Cullin 4B (CUL4B), which acts as a scaffold protein in CUL4B-RING ubiquitin ligase complexes (CRL4B), is frequently overexpressed in cancer and represses tumor suppressors through diverse epigenetic mechanisms. However, the role and the underlying mechanisms of CUL4B in regulating drug resistance remain unknown. Here, we showed that CUL4B promotes TAM resistance in breast cancer cells through a miR-32-5p/ER-α36 axis. We found that upregulation of CUL4B correlated with decreased TAM sensitivity of breast cancer cells, and knockdown of CUL4B or expression of a dominant-negative CUL4B mutant restored the response to TAM in TAM-resistant MCF7-TAM^R and T47D-TAM^R cells. Mechanistically, we demonstrated that CUL4B renders breast cancer cells TAM-resistant by upregulating ER-α36 expression, which was mediated by downregulation of miR-32-5p. We further showed that CRL4B epigenetically represses the transcription of miR-32-5p by catalyzing monoubiquitination at H2AK119 and coordinating with PRC2 and HDAC complexes to promote trimethylation at H3K27 at the promoter of miR-32-5p. Pharmacologic or genetic inhibition of CRL4B/PRC2/HDAC complexes significantly increased TAM sensitivity in breast cancer cells in vitro and in vivo. Taken together, our findings thus establish a critical role for the CUL4B-miR-32-5p-ER-α36 axis in the regulation of TAM resistance and have important therapeutic implications for combined application of TAM and the inhibitors of CRL4B/PRC2/HDAC complex in breast cancer treatment. © 2021 The Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd.

Abnormal alternative splicing promotes tumor resistance in targeted therapy and immunotherapy

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Abnormal alternative splicing is involve in abnormal expression of genes in cancer.

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Abnormal alternative splicing events promote malignant progression of cancer.

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Abnormal alternative splicing develops tumor resistance to targeted therapy by changing the target point and signal transduction pathway.

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Abnormal alternative splicing develops tumor resistance to immunotherapy by changing cell surface antigens and protein structure.

Abnormally alternative splicing events are common hallmark of diverse types of cancers. Splicing variants with aberrant functions play an important role in cancer development. Most importantly, a growing body of evidence has supported that alternative splicing might play a significant role in the therapeutic resistance of tumors. Targeted therapy and immunotherapy are the future directions of tumor therapy; however, the loss of antigen targets on the tumor cells surface and alterations in drug efficacy have resulted in the failure of targeted therapy and immunotherapy. Interestingly, abnormal alternative splicing, as a strategy to regulate gene expression, is reportedly involved in the reprogramming of cell signaling pathways and epitopes on the tumor cell surface by changing splicing patterns of genes, thus rendering tumors resisted to targeted therapy and immunotherapy. Accordingly, increased knowledge regarding abnormal alternative splicing in tumors may help predict therapeutic resistance during targeted therapy and immunotherapy and lead to novel therapeutic approaches in cancer. Herein, we provide a brief synopsis of abnormal alternative splicing events in cancer progression and therapeutic resistance.

The influence of phenolic environmental estrogen on the transcriptome of uterine leiomyoma cells: A whole transcriptome profiling-based analysis

OBJECTIVE

The study aimed to recognize potential molecular targets and signal pathways whereby phenolic environmental estrogen promotes the proliferation of uterine leiomyoma cells.

METHODS

Primary cultured cell lines of uterine leiomyoma were treated with 0.1% DMSO, 10.0μmol/L Bisphenol A (BPA), and 32.0μmol/L Nonylphenol (NP) for 48 h before RNA-seq was performed. Those genes affected by BPA and NP were identified. Then, Gene Ontology (GO) enrichment, Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment, and Protein-protein Interaction (PPI) analysis were performed. Quantitative real-time polymerase chain reaction (q-PCR) and western blot were used to verify the differentially expressed gene and protein.

RESULTS

Compared to with the control group, 739 differentially expressed genes were identified in both the BPA group and the NP group. GO enrichment analysis showed that the most enriched GO terms were connective tissue development and G1/S transition of mitotic cell cycle, and extracellular matrix. The results of KEGG enrichment analysis showed that differentially expressed mRNA were enriched mainly in three primary pathways, including environmental information processing, human diseases, and cellular processes. The cell cycle, PI3K-Akt signaling pathway are significantly enriched. The q-PCR and western blot verified the cell cycle associated genes and proteins were upregulated in both BPA group and NP group. Both BPA and NP activated the PI3K-AKT signaling pathway.

CONCLUSION

Phenolic environmental estrogens may promote the proliferation and cell cycle progression of uterine leiomyoma cells through rapid non-genomic ER signaling, which leads to disordered cell cycle regulation and accelerates the transition of the cell cycle from G0/G1 phase to S phase. In addition, as an external stimulant, phenolic estrogen promotes the upregulation of inflammatory factors in uterine leiomyomas.

CD45RO-CD8+ T cell-derived exosomes restrict estrogen-driven endometrial cancer development via the ERβ/miR-765/PLP2/Notch axis

Rationale: Estrogen-dependent cancers (e.g., breast, endometrial, and ovarian cancers) are among the leading causes of morbidity and mortality in women worldwide. Recently, exosomes released by tumor-infiltrating CD8⁺ T cells have been under the spotlight in the field of cancer immunotherapy. Our study aims at elucidating the underlying mechanisms of the crosstalk between estrogen signaling and CD8⁺ T cells, and possible intervention values in uterine corpus endometrial cancer (UCEC).

Methods: Micro RNA-seq was conducted to screen differentially expressed micro RNA in UCEC. Bioinformatic analysis was processed to predict the target of miR-765. RNA silencing or overexpressing and pharmacologic inhibitors were used to assess the functions of ERβ/miR-765/PLP2/Notch axis in UCEC cell proliferation and invasion in vivo and in vitro. In vivo imaging was performed to evaluate the metastasis of tumor in mice. Combined fluorescent in situ hybridization for miR-765 and immunofluorescent labeling for CD8 was carried out to prove the co-localization between miR-765 and CD8⁺ T cells. Exosomes derived from CD45RO^-CD8⁺ T cells were isolated to detect the regulatory effects on UCEC.

Results: miR-765 is characterized as the most downregulated miRNA in UCEC, and there is a negative correlation between miR-765 and Proteolipid protein 2 (PLP2) in UCEC lesion. Estrogen significantly down-regulates miR-765 level, and facilitates the development of UCEC by estrogen receptor (ER) β. Mechanistically, this process is mediated through the miRNAs (e.g., miR-3584-5p, miR-7-5p, miR-150-5p, and miR-124-3p) cluster-controlled regulation of the PLP2, which further regulates Ki-67 and multiple epithelial-mesenchymal transition (EMT)-related molecules (e.g, E-cadherin and Vimentin) in a Notch signaling pathway-dependent manner. Interestingly, the selective ER degrader Fulvestrant alleviates estrogen-mediated miR-765/PLP2 expression regulation and UCEC development in ERβ-dependent and -independent manners. Additionally, CD45RO^-CD8⁺ T cell-derived exosomes release more miR-765 than that from CD45RO⁺CD8⁺ T cells. In therapeutic studies, these exosomes limit estrogen-driven disease development via regulation of the miR-765/PLP2 axis.

Conclusions: This observation reveals novel molecular mechanisms underlying estrogen signaling and CD8⁺ T cell-released exosomes in UCEC development, and provides a potential therapeutic strategy for UCEC patients with aberrant ERβ/miR-765/PLP2/Notch signaling axis.