ER-α36, a novel variant of ER-α, mediates estrogen-stimulated proliferation of endometrial carcinoma cells via the PKCδ/ERK pathway

Sirtuin 1 underlies depression-related behaviors by modulating the serotonin system in the dorsal raphe nucleus in female mice

Major depressive disorder (MDD) is a primary driver of disability and greatly escalates the worldwide disease burden. Sirtuin 1 (Sirt1), a key regulator of cellular metabolism, is associated with genetic variations in MDD. We investigated how Sirt1 in serotonin (5-HT) neurons within the dorsal raphe nucleus (DRN) in mice affected behaviors associated with depression and susceptibility to stress. Our findings revealed that Sirt1 expression in the DRN was decreased when chronic unpredictable stress was induced in depressed female mice. Additionally, Sirt1 was co-localized with 5-HT neurons within the DRN, and its selective ablation in these neurons have induced depressive phenotypes in female mice but not in males. Adeno-associated virus-mediated knockdown of Sirt1 in adult female mice induced depressive behaviors, whereas Sirt1 overexpression eliminated these behaviors. Moreover, fiber-optic recordings showed a decrease in the neural excitability of 5-HT neurons and 5-HT levels in the DRN after Sirt1 knockdown. Furthermore, we observed that Sirt1 knockdown reduced the expression of tryptophan hydroxylase-2 (Tph2) and phosphorylation levels of extracellular signal-regulated kinase (ERK) and CAMP response element binding protein (CREB). Finally, variable molecular targets regarding immune responses and cytokine productions after Sirt1 knockdown were analyzed via high-throughput RNA-seq analysis of specimens from the DRN. The findings of this study emphasize the importance of Sirt1 for regulating depression-related behaviors in female mice by influencing the activity of 5-HT neurons in the DRN.

Overcoming Cancer Resistance: Strategies and Modalities for Effective Treatment

Resistance to cancer drugs is a complex phenomenon that poses a significant challenge in the treatment of various malignancies. This review comprehensively explores cancer resistance mechanisms and discusses emerging strategies and modalities to overcome this obstacle. Many factors contribute to cancer resistance, including genetic mutations, activation of alternative signaling pathways, and alterations in the tumor microenvironment. Innovative approaches, such as targeted protein degradation, immunotherapy combinations, precision medicine, and novel drug delivery systems, hold promise for improving treatment outcomes. Understanding the intricacies of cancer resistance and leveraging innovative modalities are essential for advancing cancer therapy.

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.

Single-cell analysis of gastric signet ring cell carcinoma reveals cytological and immune microenvironment features

Gastric signet ring cell carcinoma (GSRC) is a special subtype of gastric cancer (GC) associated with poor prognosis, but an in-depth and systematic study of GSRC is lacking. Here, we perform single-cell RNA sequencing to assess GC samples. We identify signet ring cell carcinoma (SRCC) cells. Microseminoprotein-beta (MSMB) can be used as a marker gene to guide the identification of moderately/poorly differentiated adenocarcinoma and signet ring cell carcinoma (SRCC). The upregulated differentially expressed genes in SRCC cells are mainly enriched in abnormally activated cancer-related signalling pathways and immune response signalling pathways. SRCC cells are also significantly enriched in mitogen-activated protein kinase and oestrogen signalling pathways, which can interact and promote each other in a positive feedback loop. SRCC cells are shown to have lower cell adhesion and higher immune evasion capabilities as well as an immunosuppressive microenvironment, which may be closely associated with the relatively poor prognosis of GSRC. In summary, GSRC exhibits unique cytological characteristics and a unique immune microenvironment, which may be advantageous for accurate diagnosis and treatment.

The Co-Expression of Estrogen Receptors ERα, ERβ, and GPER in Endometrial Cancer

Estrogens have important roles in endometrial cancer (EC) and exert biological effects through the classical estrogen receptors (ERs) ERα and ERβ, and the G-protein-coupled ER, GPER. So far, the co-expression of these three types of ERs has not been studied in EC. We investigated ERα, ERβ, GPER mRNA and protein levels, and their intracellular protein distributions in EC tissue and in adjacent control endometrial tissue. Compared to control endometrial tissue, immunoreactivity for ERα in EC tissue was weaker for nuclei with minor, but unchanged, cytoplasmic staining; mRNA and protein levels showed decreased patterns for ERα in EC tissue. For ERβ, across both tissue types, the immunoreactivity was unchanged for nuclei and cytoplasm, although EC tissues again showed lower mRNA and protein levels compared to adjacent control endometrial tissue. The immunoreactivity of GPER as well as mRNA levels of GPER were unchanged across cancer and control endometrial tissues, while protein levels were lower in EC tissue. Statistically significant correlations of estrogen receptor α (ESR1) versus estrogen receptor β (ESR2) and GPER variant 3,4 versus ESR1 and ESR2 was seen at the mRNA level. At the protein level studied with Western blotting, there was significant correlation of ERα versus GPER, and ERβ versus GPER. While in clinical practice the expression of ERα is routinely tested in EC tissue, ERβ and GPER need to be further studied to examine their potential as prognostic markers, provided that specific and validated antibodies are available.

The E3 Ligase TRIM4 Facilitates SET Ubiquitin-Mediated Degradation to Enhance ER-α Action in Breast Cancer

Estrogen receptor alpha (ER-α) action is critical for hormone-dependent breast cancer, and ER-α dysregulation can lead to the emergence of resistance to endocrine therapy. Here, it is found that TRIM4 is downregulated in tamoxifen (TAM)-resistant breast cancer cells, while the loss of TRIM4 is associated with an unfavorable prognosis. In vitro and in vivo experiments confirm that TRIM4 increased ER-α expression and the sensitivity of breast cancer cells to TAM. Mechanistically, TRIM4 is found to target SET, and TRIM4-SET interactions are mediated by the RING and B-box domains of TRIM4 and the carboxyl terminus of SET. Moreover, it is determined that TRIM4 catalyzed the K48-linked polyubiquitination of SET (K150 and K172), promoting its proteasomal degradation and disassociation from p53 and PP2A. Once released, p53 and PP2A are able to further promote ESR1 gene transcription and enhance mRNA stability. Moreover, univariate and multivariate Cox proportional hazards regression analyses confirm that TRIM4 expression is an independent predictor of overall survival and recurrence-free survival outcomes in patients with ER-α positive breast cancer. Taken together, the data highlights a previously undiscovered mechanism and suggest that TRIM4 is a valuable biomarker that can be analyzed to predict response to endocrine therapy in breast cancer patients.

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.

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.

[Estradiol activates ERK phosphorylation by binding to ERβ to inhibit proliferation and promote apoptosis of human chondrocytes]

OBJECTIVE

To explore the effect of estradiol (E2) binding to its receptor ERβ on the proliferation and apoptosis of C28I2 cells.

OBJECTIVE

We cloned the sequence of ESR2 into a recombinant adenovirus plasmid (pAd-ESR2) and packaged the plasmid in HEK293 cells. Normal human chondrocyte C28I2 cells were transfected with Ad-ESR2 or small interfering RNA targeting ESR2-siRNA (ESR2-siRNA), and the effects of treatment with DMSO or E2 on the expression of the proteins associated with endoplasmic reticulum (ER) stress and cell apoptosis were determined using Western blotting. qRT-PCR was used to detect the expressions of proliferation-related marker genes, and an EdU kit and flow cytometry were used to assess cell proliferation and apoptosis. We also tested the effects of U0126 (an ERK pathway inhibitor) and E2, alone or in combination, on ER stress, apoptosis and the ERK signaling pathway in C28I2 cells infected with Ad-ESR2 using Western blotting.

OBJECTIVE

Overexpression of Ad-ESR2 in C28I2 cells significantly promoted the expressions of IRE1α, PERK, XBP1s, and cleaved caspase-12, inhibited proliferation related marker genes PCNA, cyclin B1, cyclin D1, and decreased the level of ERK phosphorylation following E2 treatment (all P < 0.05). Interference of ESR2 caused significant reduction in the expressions of ER stress-related proteins and apoptosis-related proteins, up-regulated the genes related to cell proliferation, and increased intracellular pERK/ERK ratio in C28I2 cells. The effect of E2 binding to ERβ, which promoted the expressions of ER stress associated proteins and apoptosis related proteins, was obviously antagonized by treatment of the cells with U0126.

OBJECTIVE

The binding of E2 to ERβ promotes ER stress and apoptosis in human chondrocytes by activating ERK pathway phosphorylation inhibit cell proliferation.

Evaluating the current status of protein kinase C (PKC)-protein kinase D (PKD) signalling axis as a novel therapeutic target in ovarian cancer

Ovarian cancer, especially high grade serous ovarian cancer is one of the most lethal gynaecological malignancies with high relapse rate and patient death. Notwithstanding development of several targeted treatment and immunotherapeutic approaches, researchers fail to turn ovarian cancer into a manageable disease. Protein kinase C (PKC) and protein kinase D (PKD) are families of evolutionarily conserved serine/threonine kinases that can be activated by a plethora of extracellular stimuli such as hormones, growth factors and G-protein coupled receptor agonists. Recent literature suggests that a signalling cascade initiated by these two protein kinases regulates a battery of cellular and physiological processes involved in tumorigenesis including cell proliferation, migration, invasion and angiogenesis. In an urgent need to discover novel therapeutic interventions against a deadly pathology like ovarian cancer, we have discussed the status quo of PKC/PKD signalling axis in context of this disease. Additionally, apart from discussing the structural properties and activation mechanisms of PKC/PKD, we have provided a comprehensive review of the recent reports on tumor promoting functions of PKC isoforms and discussed the potential of PKC/PKD signalling axis as a novel target in this lethal pathology. Furthermore, in this review, we have discussed the significance of several recent clinical trials and development of small molecule inhibitors that target PKC/PKD signalling axis in ovarian cancer.

Progress in the Understanding of the Mechanism of Tamoxifen Resistance in Breast Cancer

Tamoxifen is a drug commonly used in the treatment of breast cancer, especially for postmenopausal patients. However, its efficacy is limited by the development of drug resistance. Downregulation of estrogen receptor alpha (ERα) is an important mechanism of tamoxifen resistance. In recent years, with progress in research into the protective autophagy of drug-resistant cells and cell cycle regulators, major breakthroughs have been made in research on tamoxifen resistance. For a better understanding of the mechanism of tamoxifen resistance, protective autophagy, cell cycle regulators, and some transcription factors and enzymes regulating the expression of the estrogen receptor are summarized in this review. In addition, recent progress in reducing resistance to tamoxifen is reviewed. Finally, we discuss the possible research directions into tamoxifen resistance in the future to provide assistance for the clinical treatment of breast cancer.

The miR-30a-5p/CLCF1 axis regulates sorafenib resistance and aerobic glycolysis in hepatocellular carcinoma

HCC (hepatocellular carcinoma) is a major health threat for the Chinese population and has poor prognosis because of strong resistance to chemotherapy in patients. For instance, a considerable challenge for the treatment of HCC is sorafenib resistance. The aberrant glucose metabolism in cancer cells aerobic glycolysis is associated with resistance to chemotherapeutic agents. Drug-resistance cells and tumors were exposed to sorafenib to establish sorafenib-resistance cell lines and tumors. Western blotting and real-time PCR or IHC staining were used to analyze the level of CLCF1 in the sorafenib resistance cell lines or tumors. The aerobic glycolysis was analyzed by ECAR assay. The mechanism mediating the high expression of CLCF1 in sorafenib-resistant cells and its relationships with miR-130-5p was determined by bioinformatic analysis, dual luciferase reporter assays, real-time PCR, and western blotting. The in vivo effect was evaluated by xenografted with nude mice. The relation of CLCF1 and miR-30a-5p was determined in patients' samples. In this study, we report the relationship between sorafenib resistance and increased glycolysis in HCC cells. We also show the vital role of CLCF1 in promoting glycolysis by activating PI3K/AKT signaling and its downstream genes, thus participating in glycolysis in sorafenib-resistant HCC cells. Furthermore, we also show that miR-30a-5p directly targets CLCF1 and that sorafenib-mediated suppression of miR-30a-5p results in the upregulation of CLCF1 in HCC cells resistant to sorafenib. We also found that when a cholesterol modified agomiR-30a-5p was delivered systemically to mice harboring sorafenib-resistant HCC tumors, tumor growth decreased significantly. There is an uncharacterized mechanism of biochemical resistance to hormone therapies orchestrated by the miR-30a-5p/CLCF1 axis to mediate sorafenib resistance and aerobic glycolysis in HCC. Therefore, this study indicates that targeting the miR-30a-5p/CLCF1 axis may hold promise for therapeutic intervention in HCC sorafenib resistance patients.

ERα-36 regulates progesterone receptor activity in breast cancer

Background

Alterations in estrogen and progesterone signaling, via their respective receptors, estrogen receptor alpha (ERα) and progesterone receptor (PR), respectively, are largely involved in the development of breast cancer (BC). The recent identification of ERα-36, a splice variant of ERα, has uncovered a new facet of this pathology. Although ERα-36 expression is associated with poor prognosis, metastasis development, and resistance to treatment, its predictive value has so far not been associated with a BC subtype and its mechanisms of action remain understudied.

Methods

To study ERα-36 expression in BC specimens, we performed immunochemical experiments. Next, the role of ERα-36 in progesterone signaling was investigated by generating KO clones using the CRISPR/CAS9 technology. PR signaling was also assessed by proximity ligation assay, Western blotting, RT-QPCR, and ChIP experiments. Finally, proliferation assays were performed with the IncuCyte technology and migration experiments using scratch assays.

Results

Here, we demonstrate that ERα-36 expression at the plasma membrane is correlated with a reduced disease-free survival in a cohort of 160 BC patients, particularly in PR-positive tumors, suggesting a crosstalk between ERα-36 and PR. Indeed, we show that ERα-36 interacts constitutively with PR in the nucleus of tumor cells. Moreover, it regulates PR expression and phosphorylation on key residues, impacting the biological effects of progesterone.

Conclusions

ERα-36 is thus a regulator of PR signaling, interfering with its transcriptional activity and progesterone-induced anti-proliferative effects as well as migratory capacity. Hence, ERα-36 may constitute a new prognostic marker as well as a potential target in PR-positive BC.

Distribution and Prognostic Significance of Estrogen Receptor α (ERα), Estrogen Receptor β (ERβ), and Human Epidermal Growth Factor Receptor 2 (HER-2) in Thyroid Carcinoma

Purpose

The primary aim of this study was to determine the incidence of estrogen receptor α (ERα), estrogen receptor β (ERβ), and human epidermal growth factor receptor 2 (HER-2) expression in various subtypes of thyroid carcinoma (TC) of follicular origin and the secondary aim was to correlate the expression with various clinicopathologic prognostic factors.

Methods

Immunohistochemistry analysis was performed on archival paraffin-embedded tissue sections (1991–2016). ERα, ERβ, and HER-2 expressions were correlated with clinicopathologic prognostic factors, disease recurrence, and overall survival (OS).

Results

A total of 264 TC patients were included in the study. Incidences of ERα, ERβ, and HER-2 were 8.1 vs 16.3 vs 13.9% (p=0.15), 26.6 vs 11.5 vs 36.1% (p=0.002), and 12.9 vs 2.9 vs 0% (p=0.003) in papillary thyroid carcinoma (PTC), follicular thyroid carcinoma (FTC), and poorly differentiated thyroid carcinoma (PDTC), respectively. Overall ERα had significant correlation with distant metastases (0.038) and in case of PDTC with multicentricity (p=0.037). ERβ had significant correlation with lymph node metastases (p=0.023) in FTC. HER-2 correlated with tumor size (p=0.027) only on univariate analysis. OS did not correlate with expression of any receptor.

Conclusion

ERα, ERβ, and HER-2 have differential expression and prognostic implications in different TC subtypes.

A Role for Estrogen Receptor alpha36 in Cancer Progression

Estrogen receptor α (ERα) functions as a ligand dependent transcription factor that directly binds specific estrogen responsive elements, thus regulating the transcription of estrogen sensitive genes. ERα has also been shown to be associated with the plasma membrane (membrane associated ERα, mERα), concentrated in lipid rafts, plasma membrane microdomains with a distinct lipid composition, where it transduces membrane-initiated estrogen-dependent activation of the mitogen-activated protein (MAP) kinase signaling pathway. Two isoforms of ERα have been described: the "traditional" ERα66 (66 kDa) and a lower molecular weight variant: the ERα46 (46 kDa). More recently, a novel ERα variant with a molecular mass of 36 kDa (ERα36) has been discovered. Notably, ERα36 has been found expressed in different human tumor cells, including both ER- positive and ER- negative breast cancer cells. Estrogen signaling at the cell membrane via ERα36 appears as capable of activating multiple pathways of importance for cancer aggressiveness and metastatic potential. The presence of serum autoantibodies reacting with mERα (anti-ERα Abs) in a large percentage of patients with breast cancer has recently been reported by our group. These anti-ERα Abs seem to act as estrogen agonists rapidly triggering MAP kinase pathway activation thus inducing tumor cell proliferation and overcoming cell resistance to anti-estrogen drug tamoxifen. In this review, we describe the involvement of ERα36 in different tumors. We also report the potential pathogenetic activity of anti-ERα Abs and their implication in drug resistance.

A nongenomic mechanism for "metalloestrogenic" effects of cadmium in human uterine leiomyoma cells through G protein-coupled estrogen receptor

Cadmium (Cd) is a ubiquitous environmental metal that is reported to be a "metalloestrogen." Uterine leiomyomas (fibroids) are estrogen-responsive gynecologic neoplasms that can be the target of xenoestrogens. Previous epidemiology studies have suggested Cd may be associated with fibroids. We have shown that Cd can stimulate proliferation of human uterine leiomyoma (ht-UtLM) cells, but not through classical estrogen receptor (ER) binding. Whether nongenomic ER pathways are involved in Cd-induced proliferation is unknown. In the present study, by evaluating G protein-coupled estrogen receptor (GPER), ERα36, and phospho-epidermal growth factor receptor (EGFR) expression in human tissues, we found that GPER, ERα36 and phospho-EGFR were all highly expressed in fibroids compared to patient-matched myometrial tissues. In ht-UtLM cells, cell proliferation was increased by low doses of Cd (0.1 µM and 10 µM), and this effect could be inhibited by GPER-specific antagonist (G15) pretreatment, or silencing (si) GPER, but not by siERα36. Cd-activated MAPK was dependent on GPER/EGFR transactivation, through significantly increased phospho-Src, matrix metalloproteinase-2 (MMP2) and MMP9, and heparin-binding EGF-like growth factor (HB-EGF) expression/activation. Also, phospho-Src could interact directly to phosphorylate EGFR. Overall, Cd-induced proliferation of human fibroid cells was through a nongenomic GPER/p-src/EGFR/MAPK signaling pathway that did not directly involve ERα36. This suggests that Cd may be a risk factor for uterine fibroids through cross talk between hormone and growth factor receptor pathways.

Trastuzumab induces PUMA-dependent apoptosis and inhibits tumor growth in gastric cancer

Gastric cancer (GC) is one of the most prevalent cancers worldwide. Trastuzumab has been approved for the treatment of metastatic GC, gastroesophageal junction cancer, and breast cancer. However, the mechanisms involved in trastuzumab-induced GC cell apoptosis remain largely unknown. In this study, we investigated the underlying mechanisms of trastuzumab-mediated suppression of GC cell growth both in vitro and in vivo. We found that trastuzumab treatment induces p53 upregulated modulator of apoptosis (PUMA) expression in GC cells, through the NF-κB pathway following AKT inhibition and glycogen synthase kinase 3β (GSK3β) activation. We also observed that PUMA was necessary for trastuzumab-induced apoptosis in GC cells. Moreover, PUMA deficiency suppressed apoptosis and the antitumor effect of trastuzumab in xenograft models. Finally, computerized tomography (CT) and immunohistochemistry results showed that patients with increased activation of PUMA were more sensitive to trastuzumab treatment than those with low PUMA expression. These results indicate that trastuzumab induces PUMA-dependent apoptosis and inhibits tumor growth in GC, suggesting that PUMA plays a critical role in mediating the antitumor effects of trastuzumab in GC. PUMA induction may be used as a marker of trastuzumab sensitivity.

BKCa participates in E2 inducing endometrial adenocarcinoma by activating MEK/ERK pathway

Background

The large-conductance, voltage-gated, calcium (Ca (2+))-activated potassium channel (BKCa) plays an important role in regulating Ca (2+) signaling and cell physiological function, and is aberrantly expressed in some types of cancers. The present study focuses on identifying the oncogenic potential and clinical significance of BKCa in endometrial adenocarcinoma, as well as exploring the mechanistic relevance by 17β -estradiol (E2) inducing aberrant activation of MEK1/2 and ERK1/2 via BKCa.

Methods

The expression of BKCa, ERK1/2 and p-ERK1/2 were examined by immunohistochemical staining in 263 cases, including 185 primary types I endometrial cancer tissues, 38 atypical endometrial hyperplasia tissues and 40 normal endometrium tissues. Cell growth, cycle, apoptosis rate, migration and invasion was separately tested in Ishikawa cells using siRNA-BKCa and/or E2 treatment, as well as the expression of these interested proteins by western blot analysis.

Results

We showed that expression of BKCa is significantly elevated in 185 types I endometrial adenocarcinoma tissues compared to those of the normal endometrium and atypical endometrial hyperplasia tissues. Furthermore, in vitro observations revealed that down-regulation of BKCa expression inhibited cell growth by both enhancing apoptosis and blocking G1/S transition, suppressed cell migration and invasion in Ishakiwa cells, and decreased the expression of p-MEK1/2 and p-ERK1/2. Additionally, RNAi-mediated knockdown of BKCa attenuated the increased cellular growth and invasion, as well as the elevated expression of p-MEK1/2 and p-ERK1/2 proteins, induced by E2 stimulation. More importantly, the aberrant expression of BKCa and p-ERK1/2 were closely related with poor prognostic factors in type I endometrial cancer, and up-regulated expression of p-ERK1/2 was significantly associated with shorter disease-free survival (DFS) and overall survival (OS) and was an independent prognostic factor in type I endometrial cancer patients.

Conclusion

Our results demonstrated that BKCa and the key downstream effectors p-ERK1/2 could be involved in important signaling pathways in initiation and development of endometrial adenocarcinoma and may provide a new therapeutic approach for women with endometrial cancer.

Electronic supplementary material

The online version of this article (10.1186/s12885-018-5027-9) contains supplementary material, which is available to authorized users.

Sphingosine kinase 1 activation by estrogen receptor α36 contributes to tamoxifen resistance in breast cancer

In breast cancer, 17β-estradiol (E2) plays critical roles mainly by binding to its canonical receptor, estrogen receptor (ER) α66, and eliciting genomic effects. E2 also triggers rapid, nongenomic responses. E2 activates sphingosine kinase 1 (SphK1), increasing sphingosine-1-phosphate (S1P) that binds to its receptors, leading to important breast cancer signaling. However, the E2 receptor responsible for SphK1 activation has not yet been identified. Here, we demonstrate in triple-negative breast cancer cells, which lack the canonical ERα66 but express the novel splice variant ERα36, that ERα36 is the receptor responsible for E2-induced activation of SphK1 and formation and secretion of S1P and dihydro-S1P, the ligands for S1PRs. Tamoxifen, the first-line endocrine therapy for breast cancer, is an antagonist of ERα66, but an agonist of ERα36, and, like E2, activates SphK1 and markedly increases secretion of S1P. A major problem with tamoxifen therapy is development of acquired resistance. We found that tamoxifen resistance correlated with increased SphK1 and ERα36 expression in tamoxifen-resistant breast cancer cells, in patient-derived xenografts, and in endocrine-resistant breast cancer patients. Our data also indicate that targeting this ERα36 and SphK1 axis may be a therapeutic option to circumvent endocrine resistance and improve patient outcome.

The expression of ER, PR in endometrial cancer and analysis of their correlation with ERK signaling pathway

Endometrial carcinoma (EC) is a common malignant tumor in gynecology. Its incidence and development are closely associated with the levels of estrogenic and progesterone hormone. Extracellular signal-regulated kinase (ERK) signaling pathway abnormity is associated with a variety of tumors. This study detected estrogen receptor (ER), progesterone receptor (PR), ERK1, and ERK2 expression in EC and analyzed their correlations. A total of 40 EC patients in our hospital were selected as test group, while another 40 healthy volunteers were enrolled as control group. ER, PR, ERK1, and ERK2 expression in EC tissue, para-carcinoma tissue, and normal endometrial tissue were detected by immunohistochemistry and Western blot. The positive rate of ER, PR, ERK1, and ERK2 in the test group was 50%, 40%, 60%, and 65%, respectively, which were significantly higher than those in the control (P< 0.05). ER, PR, ERK1, and ERK2 protein expressions in EC cell were significantly higher than those in the control (P< 0.05). ERK1 and ERK2 presented positive correlation with ER and PR (P< 0.05). In conclusion, EC patients presented higher expressions of ER, PR, which were correlated with higher levels of ERK1 and ERK2, suggesting they might be involved in the pathogenesis of EC.

ERα36 gene silencing promotes tau protein phosphorylation, inhibits cell proliferation, and induces apoptosis in human neuroblastoma SH-SY5Y cells

Neuroblastoma is the most common cancer in infants and the third most common cancer in children after leukemia and brain cancer. The purpose of our study was to investigate the effects of estrogen receptor (ER)-α36 gene silencing on tau protein phosphorylation, cell proliferation, and cell apoptosis in human neuroblastoma SH-SY5Y cells. SH-SY5Y cells were treated with estrogen or left untreated, to investigate the effects of estrogen stimulation on ERα36 and the ERK/protein B kinase (AKT) signaling pathway. ERα36 mRNA expressions were detected by quantitative RT-PCR. A phosphatase kit was used to test protein phosphatase (PP)-2A activity before and after treatment. Western blot analysis was conducted to detect protein expression of ERα36; tau protein; phosphorylated- tau (p-tau) at site Thr231 [p-tau (Thr231)]; glycogen synthase kinase (GSK)3β and its specificity sites (Tyr216 and Ser9); Cyclin Dl; proliferating cell nuclear antigen (PCNA); B-cell lymphoma (Bcl)-2; and Bcl-2-associated X protein (Bax). A cell-counting kit (CCK)-8 assay was used to determine cell viability. Cell apoptosis and rate of tumor growth and volume were determined by Annexin V-FITC/PI staining and a xenotransplanted tumor model in nude mice. Results show that without estrogen stimulation, ERα36 was inactivated. When stimulated by estrogen, expression of ERα36, PP2A, p-GSK3β (Ser9)/total protein ( t)-GSK3β, Cyclin Dl, PCNA, and Bcl-2 were up-regulated, and p-GSK3β (Tyr216)/ t-GSK3β expression was down-regulated, as was p-tau (Thr231) and Bax expression. The expression of p-ERK/ERK, p-AKT/AKT, p-methyl ethyl ketone (MEK)/MEK, and p-mammalian target of rapamycin (mTOR)/mTOR expression was up-regulated, suggesting that the ERK/AKT signaling pathway is activated. Cell proliferation was also accelerated, whereas apoptosis was inhibited with stimulation by estrogen. However, we found that the effects of silencing ERα36 on the expression of related intracellular factors had no association with estrogen. Our study demonstrates that ERα36 gene silencing can inhibit the activation of the ERK/AKT signaling pathway, increase tau protein phosphorylation, decrease cell vitality and tumorigenicity, and promote apoptosis of human neuroblastoma SH-SY5Y cells.-Wang, H.-B., Li, T., Ma, D.-Z., Zhi, H. ERα36 gene silencing promotes tau protein phosphorylation, inhibits cell proliferation, and induces apoptosis in human neuroblastoma SH-SY5Y cells.

Phytonutrient genistein is a survival factor for pancreatic β-cells via GPR30-mediated mechanism

We previously discovered that phytonutrient genistein rapidly activates cAMP signaling in β-cells and improves islet mass in diabetic mice. However, the mechanism underlying these actions of genistein is still unclear. Here, we show that pharmacological or molecular inhibition of Gαs blocked genistein-stimulated adenylate cyclase activity in plasma membrane and intracellular cAMP production in INS1 cells and islets. Further, genistein stimulation of cAMP generation was abolished in islets exposed to a specific GPR30 inhibitor G15 or islets from GPR30 deficient (GPR30-/-) mice. In vivo, dietary provision of genistein (0.5 g/kg diet) significantly mitigated streptozotocin-induced hyperglycemia in male WT mice, which was associated with improved blood insulin levels and pancreatic islet mass and survival, whereas these effects were absent in Gpr30-/- mice. Genistein treatment promoted survival of INS1 cells and human islets chronically exposed to palmitate and high glucose. At molecular level, genistein activated CREB phosphorylation and subsequently induced Bcl-2 expression, and knockdown of CREB diminished the protective effect of genistein on β-cells induced by lipoglucotoxicity. Finally, deletion of GPR30 in β-cells or islets ablated genistein-induced CREB phosphorylation and its cytoprotective effect. These findings demonstrate that genistein is a survival factor for β-cells via GPR30-initiated, Gαs-mediated activation of CREB.

miR-206 regulates 5-FU resistance by targeting Bcl-2 in colon cancer cells

Introduction

Previous studies have found that miRNAs play a key role in drug resistance. Multiple reports show that miRNAs act as regulators in colorectal cancer (CRC) cells, but the role of miR-206 in CRC is still not well understood. The current study aimed to explore the potential function of miR-206 in 5-FU resistance.

Methods

To indentify the role of miR-206 in 5-FU resistance, the expression of miR-206 was examined by real-time polymerase chain reaction (RT-PCR) in 5-FU-resistant (FR) CRC (HCT116/FR and RKO/FR) and their parental cell lines. miR-206 mimic was transfected to 5-FU-FR CRC, and the 5-FU sensitivity was detected by MTS and flow cytometry. Using miRNA target prediction software, we found that miR-206 could target the 3′ untranslated region (3′UTR) sequence of Bcl-2.

Results

miR-206 was found to be downregulated in 5-FU-FR CRC in comparison with their parental cell lines, suggesting its crucial relevance for colon cancer biology. Downregulation of miR-206 promoted drug resistance and decreased apoptosis of parental cells, while overexpression of miR-206 promoted drug cytotoxicity and apoptosis of HCT116/FR cells. We also identified miR-206 targeting Bcl-2 directly in CRC, which is required for miR-206 mediated-5-FU resistance.

Conclusion

Our results show that miR-206 targets Bcl-2 to mediate chemoresistance, proliferation, and apoptosis in CRC. This study provides a novel promising candidate for colon cancer therapy.

Tamoxifen enhances stemness and promotes metastasis of ERα36+ breast cancer by upregulating ALDH1A1 in cancer cells

The 66 kDa estrogen receptor alpha (ERα66) is the main molecular target for endocrine therapy such as tamoxifen treatment. However, many patients develop resistance with unclear mechanisms. In a large cohort study of breast cancer patients who underwent surgery followed by tamoxifen treatment, we demonstrate that ERα36, a variant of ERα66, correlates with poor prognosis. Mechanistically, tamoxifen directly binds and activates ERα36 to enhance the stemness and metastasis of breast cancer cells via transcriptional stimulation of aldehyde dehydrogenase 1A1 (ALDH1A1). Consistently, the tamoxifen-induced stemness and metastasis can be attenuated by either ALDH1 inhibitors or a specific ERα36 antibody. Thus, tamoxifen acts as an agonist on ERα36 in breast cancer cells, which accounts for hormone therapy resistance and metastasis of breast cancer. Our study not only reveals ERα36 as a stratifying marker for endocrine therapy but also provides a promising therapeutic avenue for tamoxifen-resistant breast cancer.

Idelalisib induces PUMA-dependent apoptosis in colon cancer cells

Idelalisib, a PI3K inhibitor, specifically targeting p110δ, has been approved for the treatment of chronic lymphocytic leukemia/small lymphocytic lymphoma and follicular lymphoma. However, the mechanisms of action of idelalisib in colon cancer cells are not well understood. We investigated how idelalisib suppresses colon cancer cells growth and potentiates effects of other chemotherapeutic drugs. In this study, we found that idelalisib treatment induces PUMA in colon cancer cells irrespective of p53 status through the p65 pathway following AKT inhibition and glycogen synthase kinase 3β (GSK3β) activation. PUMA is necessary for idelalisib-induced apoptosis in colon cancer cells. Idelalisib also synergized with 5-FU or regorafenib to induce marked apoptosis via PUMA in colon cancer cells. Furthermore, PUMA deficiency suppressed apoptosis and antitumor effect of idelalisib in xenograft model. These results demonstrate a critical role of PUMA in mediating the anticancer effects of idelalisib in colon cancer cells and suggest that PUMA induction can be used as an indicator of idelalisib sensitivity, and also have important implications for it clinical applications.

Suppressive efficiency of RASSF1A in endometrial carcinoma via inhabiting estrogen receptor alpha expression and ERK pathway activation

INTRODUCTION

Known as a tumor suppressor, the Ras association domain family 1 isoform A (RASSF1A) is implicated in many human cancers, such as endometrial carcinoma. There is little known about the tumor inhibitive effects of RASSF1A on endometrial carcinoma. The present study was designed to investigate the role of RASSF1A in HEC-1-A cells and to explore its potential mechanisms.

MATERIALS AND METHODS

In this study, overexpression of RASSF1A was established by transfection the recombinant adenoviral RASSF1A in HEC-1-A cells. Cells viability was assessed by MTT assay and the apoptosis was analyzed using flow cytometry. Cell migration and invasion were measured in Transwell assay. The levels of ERα and PELP1 protein and extracellular regulated protein kinase (ERK) pathway activation were detected by Western blot.

RESULTS

RASSF1A over-expression could significantly inhibit the proliferation, migration and invasion of the HEC-1-A cells in transfection with RASSF1A group compared to that in transfection with control group, also induced apoptosis and suppressed the tumor growth after injection in nude mice. Moreover, overexpression of RASSF1A could inhibit the ERK signal pathway activation and decrease the ERα and PELP1 expression.

CONCLUSION

Tumor suppressive efficiency of RASSF1A is exerted through the regulation of ERK pathway activation, ERα and PELP1 expression.

Concomitant high expression of ERα36, GRP78 and GRP94 is associated with aggressive papillary thyroid cancer behavior

PURPOSE

Papillary thyroid cancer (PTC) is more common in women than in men. It has been suggested that estrogen may be involved in its development, as has previously been shown for breast, endometrial and ovarian cancer. The purpose of this study was to assess correlations between the expression of the estrogen receptor alpha36 (ERα36) and the glucose regulated proteins GRP78 and GRP94 (chaperones involved in glycoprotein folding) and various PTC clinicopathological features, as well as to evaluate the potential usefulness of these three potential oncogenic proteins in the prediction of aggressive PTC behavior.

METHODS

ERα36, GRP78 and GRP94 protein expression in 218 primary PTC tissues and PTC-derived BCPAP cells was examined using immunohistochemistry, Western blotting and immunocytochemistry. The proliferative, invasive and migrative capacities of BCPAP cells in which the respective genes were either exogenously over-expressed or silenced were assessed using BrdU incorporation and Transwell assays, respectively.

RESULTS

We found that ERα36, GRP78 and GRP94 protein expression was upregulated in the primary PTC tissues tested. We also found that ERα36, GRP78 and GRP94 expression modulation affected the proliferation, invasion and migration of PTC-derived BCPAP cells. A positive correlation and a positive feedback loop were noted between ERα36, GRP78 and GRP94 protein expression in the primary PTC tissues and in BCPAP cells, respectively. High ERα36 expression in combination with a high GRP78/ GRP94 expression was found to have a stronger correlation with extrathyroid extension (ETE), lymph node metastasis (LNM), distant metastasis (DM) and high TNM stage than high ERα36 expression in combination with either high GRP78 or high GRP94 expression (p = 0.028 for ETE, p = 0.002 for DM and p ≤ 0.001 for LNM and high TNM stage) or high ERα36 expression alone (p < 0.001 for ETE, LNM, DM and high TNM stage).

CONCLUSIONS

From our data we conclude that a concomitant high expression of ERα36, GRP78 and GRP94 is strongly associated with aggressive PTC behavior and may be used as a predictor for ETE, LNM, DM and high TNM stage.

ERα36, a variant of estrogen receptor α, is predominantly localized in mitochondria of human uterine smooth muscle and leiomyoma cells

ERα36 is a naturally occurring, membrane-associated, isoform of estrogen receptor α. The expression of ERα36 is due to alternative splicing and different promoter usage. ERα36 is a dominant-negative effector of ERα66-mediated transactivational activities and has the potential to trigger membrane-initiated mitogenic, nongenomic, estrogen signaling; however, the subcellular localization of ERα36 remains controversial. To determine the cellular localization of ERα36 in estrogen-responsive human uterine smooth muscle (ht-UtSMC) and leiomyoma (fibroid; ht-UtLM) cells, we conducted systematic confocal microscopy and subcellular fractionation analysis using ERα36 antibodies. With Image J colocalizaton analysis plugin, confocal images were analyzed to obtain a Pearson’s Correlation Coefficient (PCC) to quantify signal colocalization of ERα36 with mitochondrial, endoplasmic reticulum, and cytoskeletal components in both cell lines. When cells were double-stained with an ERα36 antibody and a mitochondrial-specific dye, MitoTracker, the PCC for the two channel signals were both greater than 0.75, indicating strong correlation between ERα36 and mitochondrial signals in the two cell lines. A blocking peptide competition assay confirmed that the mitochondria-associated ERα36 signal detected by confocal analysis was specific for ERα36. In contrast, confocal images double-stained with an ERα36 antibody and endoplasmic reticulum or cytoskeletal markers, had PCCs that were all less than 0.4, indicating no or very weak signal correlation. Fractionation studies showed that ERα36 existed predominantly in membrane fractions, with minimal or undetected amounts in the cytosol, nuclear, chromatin, and cytoskeletal fractions. With isolated mitochondrial preparations, we confirmed that a known mitochondrial protein, prohibitin, was present in mitochondria, and by co-immunoprecipitation analysis that ERα36 was associated with prohibitin in ht-UtLM cells. The distinctive colocalization pattern of ERα36 with mitochondria in ht-UtSMC and ht-UtLM cells, and the association of ERα36 with a mitochondrial-specific protein suggest that ERα36 is localized primarily in mitochondria and may play a pivotal role in non-genomic signaling and mitochondrial functions.

Concomitant high expression of ERα36, EGFR and HER2 is associated with aggressive behaviors of papillary thyroid carcinomas

ERα, ERβ, PR, ERα36, EGFR and HER2 mRNA and protein expression in papillary thyroid carcinoma (PTC) were examined by real time RT-PCR and immunohistochemical staining. The mRNA and protein expression of ERα and PR were gradually increased and those of ERβ were gradually decreased from normal thyroid tissues to nodular hyperplasias (P < 0.05) and to PTCs (P < 0.05). However, the mRNA and protein expression of ERα36, EGFR and HER2 were only significantly increased in PTCs when compared with those in normal thyroid tissues (P < 0.001) and nodular hyperplasias (P < 0.001). There was some correlation between ERα, ERβ and PR, and between ERα36, EGFR and HER2 protein expression in PTCs. As for ERα, ERβ and PR, there was a significant positive correlation between ERα and PR, and a significant negative correlation between ERα and ERβ and between PR and ERβ protein expression. As for ERα36, EGFR and HER2, there was a significant positive correlation between ERα36, EGFR and HER2 protein expression in PTCs. Concomitant high expression of ERα36, EGFR and HER2 was strongly associated with aggressive behaviors including extrathyroidal extension (ETE), lymph node metastasis (LNM) and high TNM stage in PTCs (P < 0.001).

ER-α36 Interactions With Cytosolic Molecular Network in Acquired Tamoxifen Resistance

According to the World Health Organization (WHO) published data in 2015; breast cancer is the most prevalent and the second leading cause of cancer death among females. As approximately 70% of breast cancer tumor cells are estrogen receptor (ER) positive, primary therapeutic agents such as Anti-estrogens were produced mostly in a way to target this receptor. Anti-estrogen therapies mostly target Estrogen receptor and block its underlying signaling pathways. Nevertheless, resistance to these agents made the condition more complicated. Recently the role of one molecule in the resistance development has been studied in some cases: ER-α36 is a 36 kDa variant of estrogen receptor molecule which is mostly absent in normal breast cells. Its interactions with epidermal growth factor receptors and ER-α66 leads in over-activation and/or over-expression of estrogen-independent pathways and suppression of estrogen-dependent pathways; they all in turn, will maintain tumor cell's growth even in the presence of tamoxifen. In this mini-review, we mainly surveyed different pathways which ER-α36 could lead to tamoxifen resistance. We also briefly mentioned how ER-α36 could switch the growth cascades from estrogen dependent into independent and make this resistance network become even more complicated.

The role of sex hormones and steroid receptors on female reproductive cancers

Sex steroids have been widely described to be associated with a number of human diseases, including hormone-dependent tumors. Several studies have been concerned about the factors regulating the availability of sex steroids and its importance in the pathophysiological aspects of the reproductive cancers in women. In premenopausal women, large fluctuations in the concentration of circulating estradiol (E2) and progesterone (P4) orchestrate many events across the menstrual cycle. After menopause, the levels of circulating E2 and P4 decline but remain at high concentration in the peripheral tissues. Notably, there is a strong relationship between circulating sex hormones and female reproductive cancers (e.g. ovarian, breast, and endometrial cancers). These hormones activate a number of specific signaling pathways after binding either to estrogen receptors (ERs), especially ERα, ERα36, and ERβ or progesterone receptors (PRs). Importantly, the course of the disease will depend on particular transactivation pathway. Identifying ER- or PR-positive tumors will benefit patients in terms of proper endocrine therapy. Based on hormonal responsiveness, effective prevention methods for ovarian, breast, and endometrial cancers represent a special opportunity for women at risk of malignancies. Hormone replacement therapy (HRT) might significantly increase the risk of these cancer types, and endocrine treatments targeting ER signaling may be helpful against E2-dependent tumors. This review will present the role of sex steroids and their receptors associated with the risk of developing female reproductive cancers, with emphasis on E2 levels in pre and postmenopausal women. In addition, new therapeutic strategies for improving the survival rate outcomes in women will be addressed.

The molecular mechanisms underlying the ERα-36-mediated signaling in breast cancer

Alterations in estrogen-mediated cellular signaling have largely been implicated in the pathogenesis of breast cancer. Here, we investigated the signaling regulation of a splice variant of the estrogen receptor, namely estrogen receptor (ERα-36), associated with a poor prognosis in breast cancers. Coupling in vitro and in vivo approaches we determined the precise sequential molecular events of a new estrogen signaling network in an ERα-negative cell line and in an original patient-derived xenograft. After estrogen treatment, ERα-36 rapidly associates with Src at the level of the plasma membrane, initiating downstream cascades, including MEK1/ERK activation and paxillin phosphorylation on S126, which in turn triggers a higher expression of cyclin D1. Of note, the direct binding of ERα-36 to ERK2 prevents its dephosphorylation by MKP3 and enhances the downstream signaling. These findings improve our understanding of the regulation of non-genomic estrogen signaling and open new avenues for personalized therapeutic approaches targeting Src or MEK in ERα-36-positive patients.

Editor's Highlight: Development of an In vitro Assay Measuring Uterine-Specific Estrogenic Responses for Use in Chemical Safety Assessment

A toxicity pathway approach was taken to develop an in vitro assay using human uterine epithelial adenocarcinoma (Ishikawa) cells as a replacement for measuring an in vivo uterotrophic response to estrogens. The Ishikawa cell was determined to be fit for the purpose of recapitulating in vivo uterine response by verifying fidelity of the biological pathway components and the dose-response predictions to women of child-bearing age. Expression of the suite of estrogen receptors that control uterine proliferation (ERα66, ERα46, ERα36, ERβ, G-protein coupled estrogen receptor (GPER)) were confirmed across passages and treatment conditions. Phenotypic responses to ethinyl estradiol (EE) from transcriptional activation of ER-mediated genes, to ALP enzyme induction and cellular proliferation occurred at concentrations consistent with estrogenic activity in adult women (low picomolar). To confirm utility of this model to predict concentration-response for uterine proliferation with xenobiotics, we tested the concentration-response for compounds with known uterine estrogenic activity in humans and compared the results to assays from the ToxCast and Tox21 suite of estrogen assays. The Ishikawa proliferation assay was consistent with in vivo responses and was a more sensitive measure of uterine response. Because this assay was constructed by first mapping the key molecular events for cellular response, and then ensuring that the assay incorporated these events, the resulting cellular assay should be a reliable tool for identifying estrogenic compounds and may provide improved quantitation of chemical concentration response for in vitro-based safety assessments.

K-Ras stabilization by estrogen via PKCδ is involved in endometrial tumorigenesis

Estrogens are considered as a major risk factor of endometrial cancer. In this study, we identified a mechanism of tumorigenesis in which K-Ras protein is stabilized via estrogen signaling through the ER-α36 receptor. PKCδ was shown to stabilize K-Ras specifically via estrogen signaling. Estrogens stabilize K-Ras via inhibition of polyubiquitylation-dependent proteasomal degradation. Estrogen-induced cellular transformation was abolished by either K-Ras or PKCδ knockdown. The role of PKCδ in estrogen-induced tumorigenesis was confirmed in a mouse xenograft model by reduction of tumors after treatment with rottlerin, a PKCδ inhibitor. Finally, levels of PKCδ correlated with that of Ras in human endometrial tumor tissues. Stabilization of K-Ras by estrogen signaling involving PKCδ up-regulation provides a potential therapeutic approach for treatment of endometrial cancer.

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

Prevailing wisdom is that estrogen receptor (ER)-α mediated genomic estrogen signaling is responsible for estrogen-stimulated cell proliferation and development of ER-positive breast cancer. However, accumulating evidence indicates that another estrogen signaling pathway, non-genomic or rapid estrogen signaling, also plays an important role in mitogenic estrogen signaling. Previously, our laboratory cloned a 36 kDa variant of ER-α, ER-α36, and found that ER-α36 is mainly expressed in the cytoplasm and at the plasma membrane. ER-α36 mediates rapid estrogen signaling and inhibits genomic estrogen signaling. In this review, we review and update the biological function of ER-α36 in ER-positive and -negative breast cancer, breast cancer stem/progenitor cells and tamoxifen resistance, potential interaction and cross-talk of ER-α36 with other ERs and growth factor receptors, and intracellular pathways of ER-α36-mediated rapid estrogen signaling. The potential function and underlying mechanism of ER-α in development of ER-positive breast cancer will also be discussed.

ERα36--Another piece of the estrogen puzzle

Although the nuclear action of estrogen receptors (ER) is a well-known fact, evidence supporting membrane estrogen receptors is steadily accumulating. New ER variants of unrecognized function have been discovered. ERα is a product of the ESR1 gene. It serves not only as a template for the full-length 66kDa protein, but also for smaller isoforms which exist as independent receptors. The recently discovered ERα36 (36kDa), consisting of 310 amino acids of total 595 ERα66 protein residues, is an example of that group. The transcription initiation site is identified in the first intron of the ESR1 gene. C-Terminal 27 amino acids are encoded by previously unknown exon 9. The presence of this unique C-terminal sequence creates an opportunity for the production of selective antibodies. ERα36 has been shown to have a high affinity to the cell membrane and as much as 90% of the protein can be bound with it. Post-translational palmitoylation is suspected to play a crucial role in ERα36 anchoring to the cell membrane. In silico analysis suggests the existence of a potential transmembrane domain in ERα36. ERα36 was found in most cells of animals at various ages, but its exact physiological function remains to be fully elucidated. It seems that cells traditionally considered as being deprived of ER are able to respond to hormonal stimulation via the ERα36 receptor. Moreover, ERα36 displays unique pharmacological properties and its action may be behind antiestrogen resistance. The use of ERα36 in cancer diagnosis gives rise to great expectations.

Role of ER-α36 in breast cancer by typical xenoestrogens

About 10 years have passed since the discovery of the estrogen receptor subtype, estrogen receptor alpha 36 (ER-α36). The relationship between cancerous cells and ER-α36 in mediating xenoestrogens (XEs) is a significant issue in the progression and treatment of breast cancer. XEs can combine with classical estrogen receptors and other receptor subtypes especially ER-α36, resulting in activation of nongenomic pathways as well as genomic pathways. Recently, most laboratories have focused on further study into the rapidly nongenomic mechanisms by overexpressing or knocking down ER-α36 in breast cancer cell lines. These rapid responses can induce the deregulation of cell cycle, and then lead to the abnormal proliferation and differentiation by regulating distinct downstream pathways. It appears that ER-α36 is a key factor in increasing risk of breast cancer. However, in several recent studies, the action mechanisms of ER-α36 by XEs in breast cancer cell lines are not always clear. In this review, we firstly summarize the expression pattern and tumor biology of ER-α36, then discuss these related estrogenic effects of ER-α36, and lastly give the predictive and prognostic value of ER-α36 as diagnostic marker by mediating typical XEs in breast cancer.

Curcumin suppresses migration and invasion of human endometrial carcinoma cells

Curcumin, a widely used Chinese herbal medicine, has historically been used in anti-cancer therapies. However, the anti-metastatic effect and molecular mechanism of curcumin in endometrial carcinoma (EC) are still poorly understood. The purpose of this study was to detect the anti-metastatic effects of curcumin and the associated mechanism(s) in EC. Based on assays carried out in EC cell lines, it was observed that curcumin inhibited EC cell migration and invasion in vitro. Furthermore, following treatment with curcumin for 24 h, there was a decrease in the expression levels of matrix metalloproteinase (MMP)-2 and -9 as well as proteinase activity in EC cells. Moreover, curcumin treatment significantly decreased the levels of the phosphorylated form of extracellular signal-regulated kinase (ERK) 1/2. MEK1 overexpression partially blocked the anti-metastatic effects of curcumin. Combined treatment with ERK inhibitor U0126 and curcumin resulted in a synergistic reduction in MMP-2/-9 expression; the invasive capabilities of HEC-1B cells were also inhibited. In conclusion, curcumin inhibits tumor cell migration and invasion by reducing the expression and activity of MMP-2/9 via the suppression of the ERK signaling pathway, suggesting that curcumin is a potential therapeutic agent for EC.

From ERα66 to ERα36: a generic method for validating a prognosis marker of breast tumor progression

Background

Estrogen receptor alpha36 (ERalpha36), a variant of estrogen receptor alpha (ER) is expressed in about half of breast tumors, independently of the [ER+]/[ER-] status. In vitro, ERalpha36 triggers mitogenic non-genomic signaling and migration ability in response to 17beta-estradiol and tamoxifen. In vivo, highly ERalpha36 expressing tumors are of poor outcome especially as [ER+] tumors are submitted to tamoxifen treatment which, in turn, enhances ERalpha36 expression.

Results

Our study aimed to validate ERalpha36 expression as a reliable prognostic factor for cancer progression from an estrogen dependent proliferative tumor toward an estrogen dispensable metastatic disease. In a retrospective study, we tried to decipher underlying mechanisms of cancer progression by using an original modeling of the relationships between ERalpha36, other estrogen and growth factor receptors and metastatic marker expression. Nonlinear correlation analyses and mutual information computations led to characterize a complex network connecting ERalpha36 to either non-genomic estrogen signaling or to metastatic process.

Conclusions

This study identifies ERalpha36 expression level as a relevant classifier which should be taken into account for breast tumors clinical characterization and [ER+] tumor treatment orientation, using a generic approach for the rapid, cheap and relevant evaluation of any candidate gene expression as a predictor of a complex biological process.

Electronic supplementary material

The online version of this article (doi:10.1186/s12918-015-0178-7) contains supplementary material, which is available to authorized users.

Estrogen activation of the mitogen-activated protein kinase is mediated by ER-α36 in ER-positive breast cancer cells

It is well known that there are two estrogen-signaling pathways, genomic estrogen signaling and non-genomic or rapid estrogen signaling. Although both ER-α and ER-β have been suggested to mediate both genomic and non-genomic estrogen signaling, rapid estrogen signaling such as activation of the MAPK/ERK signaling in ER-positive breast cancer MCF7 cells has been controversial. Previously, our laboratory cloned a 36kDa variant of ER-α, ER-α36, that is mainly localized at the plasma membrane and is able to mediate rapid estrogen signaling. In this study, we investigated the function and the underlying mechanisms of ER-α36 in rapid estrogen signaling of ER-positive breast cancer cells. ER-positive breast cancer cells MCF7, T47D and H3396 as well as their variants with different levels of ER-α and ER-α36 expression were used to examine estrogen induction of the MAPK/ERK1/2 signaling. The underlying mechanisms were also studied in these cells with the neutralizing antibodies and chemical inhibitors against different growth factors and their receptors. We found that ER-α36 mediated estrogen induction of the MAPK/ERK phosphorylation in ER-positive breast cancer cells while the full-length ER-α failed to do so. The rapid estrogen signaling mediated by ER-α36 involved a orchestrated action of matrix metalloproteinases (MMPs), heparin-binding epidermal growth factor (HB-EGF), amphiregulin, insulin-like growth factor 1 receptor (IGF-1R), epidermal growth factor receptor (EGFR), HER2/Neu and Src. Our results thus indicated that ER-α36 is the estrogen receptor that mediates estrogen induction of the MAPK/ERK signaling in ER-positive breast cancer cells.

ER-α36: a novel biomarker and potential therapeutic target in breast cancer

Estrogen receptor-alpha36 (ER-α36) is a 36-kDa variant of estrogen receptor-alpha (ER-α) firstly identified and cloned by Wang et al in 2005. It lacks both transactivation domains (activation function 1 and activation function 2) and has different biological characteristics compared to traditional ER-α (ER-α66). ER-α36 primarily locates on plasma membrane and cytoplasm and functions as a mediator in the rapid membrane-initiated non-genomic signaling pathway. Additionally, it inhibits the traditional genomic signaling pathway mediated by ER-α66 in a dominant-negative pattern. Accumulating evidence has demonstrated that ER-α36 regulates the physiological function of various tissues. Thus, dysregulation of ER-α36 is closely associated with plenty of diseases including cancers. ER-α36 is recognized as a molecular abnormality which solidly correlates to carcinogenesis, aggressiveness, and therapeutic response of breast cancer. Additionally, special attention has been paid to the role of ER-α36 in endocrine therapy resistance. Therefore, ER-α36 provides a novel biomarker of great value for diagnosis, prognosis, and treatment of breast cancer. It may also be a potential therapeutic target for breast cancer patients, especially for those who are resistant to endocrine therapy. In this review, we will overview and update the biological characteristics, underlying mechanism, and function of ER-α36, focusing on its biological function in breast cancer and endocrine therapy resistance. We will evaluate its application value in clinical practice.

The wedelolactone derivative inhibits estrogen receptor-mediated breast, endometrial, and ovarian cancer cells growth

Estrogen and estrogen receptor (ER)-mediated signaling pathways play important roles in the etiology and progression of human breast, endometrial, and ovarian cancers. Attenuating ER activities by natural products and their derivatives is a relatively practical strategy to control and reduce breast, endometrial, and ovarian cancer risk. Here, we found 3-butoxy-1,8,9-trihydroxy-6H-benzofuro[3,2-c]benzopyran-6-one (BTB), a new derivative of wedelolactone, could effectively inhibit the 17-estradiol (E2)-induced ER transactivation and suppress the growth of breast cancer as well as endometrial and ovarian cancer cells. Our results indicate that 2.5 μM BTB effectively suppresses ER-positive, but not ER-negative, breast, endometrial, and ovarian cancer cells. Furthermore, our data indicate that BTB can modulate ER transactivation and suppress the expression of E2-mediated ER target genes (Cyclin D1, E2F1, and TERT) in the ER-positive MCF-7, Ishikawa, and SKOV-3 cells. Importantly, this BTB mediated inhibition of ER activity is selective since BTB does not suppress the activities of other nuclear receptors, including glucocorticoid receptor and progesterone receptor, suggesting that BTB functions as a selective ER signaling inhibitor with the potential to treat breast, endometrial, and ovarian cancers.

The therapeutic target of estrogen receptor-alpha36 in estrogen-dependent tumors

Estrogen receptor-alpha36 (ER-α36) is a new isoform of estrogen receptors without transcriptional activation domains of the classical ER-α(ER - α66). ER-α36 is mainly located in cytoplasm and plasma membrane. ER-α36 mediates non-genomic signaling and is involved in genomic signaling of other ERs. Recently ER-α36 is found to play a critical role in the development of estrogen-dependent cancers and endocrine resistance of breast cancer. The present article overviews and updates the biological nature and function of ER-α36, potential interaction of ER-α36 with other estrogen receptors and growth factor receptors, intracellular signaling pathways, potential mechanism by which ER-α36 may play an important role in the development of tumor resistance to endocrine therapies.

Estrogen biosynthesis, phase I and phase II metabolism, and action in endometrial cancer

Endometrial cancer is the most common gynecological malignancy in the developed World. Based on their histopathology, clinical manifestation, and epidemiology, the majority of endometrial cancer cases can be divided into two groups: the more prevalent type 1 which is associated with unopposed estrogen exposure; and the less common type 2, which is usually not associated with hyper-estrogenic factors. This manuscript overviews the published data on the expression of genes encoding the estrogen biosynthetic enzymes, the phase I and phase II estrogen metabolic enzymes, and the estrogen receptors in endometrial cancer, at the mRNA, protein and enzyme activity levels. The potential role of altered expression of these enzymes and receptors in cancerous versus control endometrial tissue, and the implication of estrogens in tumor initiation and promotion, are discussed. Finally, based on the published data, a model of estrogen metabolism and actions is proposed for pre-cancerous and cancerous endometrial tissue, and the role of the estrogens in the progression of endometrial cancer from endometrial hyperplasia is suggested.

Non-genomic estrogen regulation of ion transport and airway surface liquid dynamics in cystic fibrosis bronchial epithelium

Male cystic fibrosis (CF) patients survive longer than females and lung exacerbations in CF females vary during the estrous cycle. Estrogen has been reported to reduce the height of the airway surface liquid (ASL) in female CF bronchial epithelium. Here we investigated the effect of 17β-estradiol on the airway surface liquid height and ion transport in normal (NuLi-1) and CF (CuFi-1) bronchial epithelial monolayers. Live cell imaging using confocal microscopy revealed that airway surface liquid height was significantly higher in the non-CF cells compared to the CF cells. 17β-estradiol (0.1–10 nM) reduced the airway surface liquid height in non-CF and CF cells after 30 min treatment. Treatment with the nuclear-impeded Estrogen Dendrimer Conjugate mimicked the effect of free estrogen by reducing significantly the airway surface liquid height in CF and non-CF cells. Inhibition of chloride transport or basolateral potassium recycling decreased the airway surface liquid height and 17β-estradiol had no additive effect in the presence of these ion transporter inhibitors. 17β-estradiol decreased bumetanide-sensitive transepithelial short-circuit current in non-CF cells and prevented the forskolin-induced increase in ASL height. 17β-estradiol stimulated an amiloride-sensitive transepithelial current and increased ouabain-sensitive basolateral short-circuit current in CF cells. 17β-estradiol increased PKCδ activity in CF and non-CF cells. These results demonstrate that estrogen dehydrates CF and non-CF ASL, and these responses to 17β-estradiol are non-genomic rather than involving the classical nuclear estrogen receptor pathway. 17β-estradiol acts on the airway surface liquid by inhibiting cAMP-mediated chloride secretion in non-CF cells and increasing sodium absorption via the stimulation of PKCδ, ENaC and the Na⁺/K⁺ATPase in CF cells.