ERα, microRNAs, and the epithelial-mesenchymal transition in breast cancer

Deciphering the TCF19/miR-199a-5p/SP1/LOXL2 pathway: Implications for breast cancer metastasis and epithelial-mesenchymal transition

Globally, breast cancer (BC) is the predominant malignancy with a significant death rate due to metastasis. The epithelial-mesenchymal transition (EMT) is a fundamental initiator for metastatic progression. Through advanced computational strategies, TCF19 was identified as a critical EMT-associated gene with diagnostic and prognostic significance in BC, based on a novel EMT score. Molecular details and the pro-EMT impact of the TCF19/miR-199a-5p/SP1/LOXL2 axis were explored in BC cell lines through in vitro validations, and the oncogenic and metastatic potential of TCF19 and LOXL2 were investigated using subcutaneous and tail-vein models. Additionally, BC-specific enrichment of TCF19 and LOXL2 was measured using a distribution landscape driven by diverse genomic analysis techniques. Molecular pathways revealed that TCF19-induced LOXL2 amplification facilitated migratory, invasive, and EMT activities of BC cells in vitro, and promoted the growth and metastatic establishment of xenografts in vivo. TCF19 decreases the expression of miR-199a-5p and alters the nuclear dynamics of SP1, modulating SP1's affinity for the LOXL2 promoter, leading to increased LOXL2 expression and more malignant characteristics in BC cells. These findings unveil a novel EMT-inducing pathway, the TCF19/miR-199a-5P/SP1/LOXL2 axis, highlighting the pivotal role of TCF19 and suggesting potential for novel therapeutic approaches for more focused BC interventions.

The role of telocytes and miR-21-5p in tumorigenicity and metastasis of breast cancer stem cells

BACKGROUND

This study aims to investigate the roles of telocytes on the metastatic properties of breast cancer stem cells (CSCs), and to re-evaluate the effect of miR-21-5p expression on CSCs following the addition of telocytes.

METHODS AND RESULTS

Telocytes from human bone marrow mononuclear cells were isolated/characterised. This was followed by the isolation/characterisation of CSCs from the MDA-MB-231. miR-21-5p was both overexpressed/inhibited in CSCs. Through co-culture studies, EMT transition and oncogenic properties of CSCs were investigated by analysing changes in ALDH1 and vimentin protein levels as well as changes in the ABCC11, SNAI1, LZTFL1, Oct 3/4, E- and N-cadherin gene expression levels. With the inhibition of miR-21-5p, significant increases in LZTFL and ABCC11 were observed with the addition of telocytes. The expression of the LZTFL gene, which decreased with the overexpression of miR-21-5p, increased in CSCs after co-culture with telocytes. While an increase expression of ABCC11, SNAI1, N-Cadherin, vimentin and ALDH was observed in CSCs after overexpression of miR-21-5p, significant decreases in these expressions were observed after co-culture with telocyte.

CONCLUSIONS

In our study, by gene/protein level analysis we demonstrated that telocytes may have the potential to reduce cancer metastasis through miR-21-5p in breast cancer progression and reduce EMT transition.

Subtype Transdifferentiation in Human Cancer: The Power of Tissue Plasticity in Tumor Progression

The classification of tumors into subtypes, characterized by phenotypes determined by specific differentiation pathways, aids diagnosis and directs therapy towards targeted approaches. However, with the advent and explosion of next-generation sequencing, cancer phenotypes are turning out to be far more heterogenous than initially thought, and the classification is continually being updated to include more subtypes. Tumors are indeed highly dynamic, and they can evolve and undergo various changes in their characteristics during disease progression. The picture becomes even more complex when the tumor responds to a therapy. In all these cases, cancer cells acquire the ability to transdifferentiate, changing subtype, and adapt to changing microenvironments. These modifications affect the tumor's growth rate, invasiveness, response to treatment, and overall clinical behavior. Studying tumor subtype transitions is crucial for understanding tumor evolution, predicting disease outcomes, and developing personalized treatment strategies. We discuss this emerging hallmark of cancer and the molecular mechanisms involved at the crossroads between tumor cells and their microenvironment, focusing on four different human cancers in which tissue plasticity causes a subtype switch: breast cancer, prostate cancer, glioblastoma, and pancreatic adenocarcinoma.

The TGFβ2-Snail1-miRNATGFβ2 Circuitry is Critical for the Development of Aggressive Functions in Breast Cancer

There have been contradictory reports on the biological role of transforming growth factor-βs (TGFβs) in breast cancer (BC), especially with regard to their ability to promote epithelial-mesenchymal transition (EMT). Here, we show that TGFβ2 is preferentially expressed in mesenchymal-like BCs and maintains the EMT phenotype, correlating with cancer stem cell-like characteristics, growth, metastasis and chemo-resistance and predicting worse clinical outcomes. However, this is only true in ERα- BC. In ERα+ luminal-type BC, estrogen receptor interacts with p-Smads to block TGFβ signalling. Furthermore, we also identify a microRNAs (miRNAs) signature (miRNAsTGFβ2 ) that is weakened in TGFβ2-overexpressing BC cells. We discover that TGFβ2-Snail1 recruits enhancer of zeste homolog-2 to convert miRNAsTGFβ2 promoters from an active to repressive chromatin configuration and then repress miRNAsTGFβ2 transcription, forming a negative feedback loop. On the other hand, miRNAsTGFβ2 overexpression reverses the mesenchymal-like traits in agreement with the inhibition of TGFβ2-Snail1 signalling in BC cells. These findings clarify the roles of TGFβ2 in BC and suggest novel therapeutic strategies based on the TGFβ2-Snail1-miRNAsTGFβ2 loop for a subset type of human BCs.

Single-Cell Transcription Mapping of Murine and Human Mammary Organoids Responses to Female Hormones

During female adolescence and pregnancy, rising levels of hormones result in a cyclic source of signals that control the development of mammary tissue. While such alterations are well understood from a whole-gland perspective, the alterations that such hormones bring to organoid cultures derived from mammary glands have yet to be fully mapped. This is of special importance given that organoids are considered suitable systems to understand cross species breast development. Here we utilized single-cell transcriptional profiling to delineate responses of murine and human normal breast organoid systems to female hormones across evolutionary distinct species. Collectively, our study represents a molecular atlas of epithelial dynamics in response to estrogen and pregnancy hormones.

Secretomics reveals hormone-therapy of breast cancer may induce survival by facilitating hypercoagulation and immunomodulation in vitro

Tumour cell haematogenous dissemination is predicated on molecular changes that enhance their capacity for invasion and preparation of the pre-metastatic niche. It is increasingly evident that platelets play an essential role in this transformation. The systemic nature of signalling molecules and extravascular factors that participate in mediating platelet-tumour cell interactions led to the development of an in vitro co-culture using whole blood and breast tumour cells, allowing us to decipher the impact of hormone-therapy on tumour cells and associated changes in the plasma proteome. Using mass spectrometry, we determined dysregulation of proteins associated with maintaining an invasive tumour phenotype. Tumour changes in genes associated with EMT and survival were documented. This is postulated to be induced via tumour cell interactions with the coagulatory and immune systems. Results highlight tumour cell adaptability to both treatment and blood resulting in a pro-tumorigenic response and a hypercoagulatory state. We illustrate that the breast cancer cell secretome can be altered by hormone-therapy, subject to the tumour subphenotype and linked to platelet activation. More sophisticated co-culture systems are required to recapitulate these interactions to better understand tumorigenesis. Moreover, deeper plasma profiling, using abundant protein depleted and/or vesicle enriched strategies, will likely reveal additional secretory proteins related to tumour cell-platelet interactions.

Methylation of ESR1 promoter induced by SNAI2-DNMT3B complex promotes epithelial-mesenchymal transition and correlates with poor prognosis in ERα-positive breast cancers

Estrogen receptor α (ERα) serves as an essential therapeutic predictor for breast cancer (BC) patients and is regulated by epigenetic modification. Abnormal methylation of cytosine phosphoric acid guanine islands in the estrogen receptor 1 (ESR1) gene promoter could silence or decrease ERα expression. In ERα-negative BC, we previously found snail family transcriptional repressor 2 (SNAI2), a zinc-finger transcriptional factor, recruited lysine-specific demethylase 1 to the promoter to transcriptionally suppress ERα expression by demethylating histone H3 lysine 4 dimethylation (H3K4me2). However, the role of SNAI2 in ERα-positive BC remains elusive. In this study, we observed a positive correlation between SNAI2 and ESR1 methylation, and SNAI2 promoted ESR1 methylation by recruiting DNA methyltransferase 3 beta (DNMT3B) rather than DNA methyltransferase 1 (DNMT1) in ERα-positive BC cells. Subsequent enrichment analysis illustrated that ESR1 methylation is strongly correlated with cell adhesion and junction. Knocking down DNMT3B could partially reverse SNAI2 overexpression-induced cell proliferation, migration, and invasion. Moreover, high DNMT3B expression predicted poor relapse-free survival and overall survival in ERα-positive BC patients. In conclusion, this study demonstrated the novel mechanisms of the ESR1 methylation mediated with the SNAI2/DNMT3B complex and enhanced awareness of ESR1 methylation's role in promoting epithelial-mesenchymal transition in BC.

Single-cell transcription mapping of murine and human mammary organoids responses to female hormones

During female adolescence and pregnancy, rising levels of hormones result in a cyclic source of signals that control the development of mammary tissue. While such alterations are well understood from a whole-gland perspective, the alterations that such hormones bring to organoid cultures derived from mammary glands have yet to be fully mapped. This is of special importance given that organoids are considered suitable systems to understand cross species breast development. Here we utilized single-cell transcriptional profiling to delineate responses of murine and human normal breast organoid systems to female hormones across evolutionary distinct species. Collectively, our study represents a molecular atlas of epithelial dynamics in response to estrogen and pregnancy hormones.

The effect of hesperetin on estrogen receptor gene expression and its relationship with the downstream pathways of estrogen receptor alpha

BACKGROUND

Estrogen receptor (ER) is a transcription factor that affects the expression of some genes involved in the progression and development of breast cancer (BC). Hesperetin (Hst) is a flavonoid that inhibits the proliferation of BC cells. In this study, we investigated the effect of Hst on the cell viability of MCF-7 cells and the gene expression of the ERα, ERβ, IL-6, Ps2, and Cyclin D1.

METHODS

In this study, cell viability was determined by MTT assay. The cells were seeded in RPMI-1640 medium and then exposed to different concentrations of Hst (0, 25, 50, 100, 200, and 400 µM) for 24 h, and IC50 was calculated. Real-time PCR was used to assess the expression of ERα, ERβ, pS2, Cyclin D1, and IL-6 mRNA. MCF-7 cells were seeded in RPMI-1640 medium and then exposed to different concentrations of Hst (0, 25, 50, 100, and 200 µM) for 24 h. Real-time PCR was carried out using a Step One Real-Time PCR System (ABI, USA) and Amplicon SYBR Green reagents.

RESULTS

The MTT assay revealed increased cytotoxicity with higher concentrations of Hst, and the IC50 was calculated at 200 µM. Real-time PCR analysis following treatment with Hst showed a significant increase in ERα gene expression at 25 µM of Hst and a decrease in expression at 50, 100, and 200 µM of Hst (p < 0.0001). ERβ gene expression significantly decreased across all concentrations of Hst (p < 0.0001), while IL-6 gene expression decreased significantly in all concentrations (p < 0.0001). pS2 gene expression increased significantly with all concentrations of Hst (p < 0.0001), while Cyclin D1 gene expression did not significantly decrease upon Hst exposure (p > 0.05).

CONCLUSIONS

The results of our study demonstrate that Hst has the ability to induce cell death in MCF-7 cells. Furthermore, it was observed that Hst reduces the expression of the ER gene and enhances its activity, which can affect the downstream pathways of the ER.

LINC01116 affects patient survival differently and is dissimilarly expressed in ER+ and ER- breast cancer samples

BACKGROUND

Breast cancer is the most commonly detected cancer and one of the leading causes of cancer mortality. Emerging evidence supports that aberrant expression of lncRNAs is correlated with tumor progression and various aspects of tumor development.

AIM

This study aimed to evaluate the expression pattern of LINC01116 in breast cancer tissues and investigate the impact of LINC01116 on patients' survival.

METHODS AND RESULTS

Microarray and qRT-PCR data analysis were performed, and the KM-plotter database was used in this study. In addition, the gain of function approach was performed to examine the effect of LINC01116 on breast cancer cells in-vitro. The results exhibited that LINC01116 is meaningfully upregulated in the ER+ tumor specimens compared to the ER- ones. Also, relative to normal tissues, the expression of LINC01116 in ER+ and ER- tumor tissues significantly increased and decreased, respectively. ROC curve analysis revealed the power of LINC01116 in distinguishing ER+ from ER- samples. Additionally, the Kaplan-Meier survival analysis showed that the LINC01116 expression positively correlates with survival probability in all as well as ER+ patients. However, this correlation was negative in ER- patients. Furthermore, our results showed that the overexpression of LINC01116 induces TGF-β signaling in ER- cells (MDA-MB-231), and microarray data analysis revealed that LINC01116 is significantly upregulated in 17β-Estradiol treated MCF7 cells.

CONCLUSION

In conclusion, our results suggest that LINC01116 can be a potential biomarker in distinguishing ER+ and ER- tissues and has different effects on patients' survival based on ER status by affecting TGF-β and ER signaling.

Effects of Hyaluronan on Breast Cancer Aggressiveness

The expression of the estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) in breast cancer cells is critical for determining tumor aggressiveness and targeting therapies. The presence of such receptors allows for the use of antagonists that effectively reduce breast cancer growth and dissemination. However, the absence of such receptors in triple-negative breast cancer (TNBC) reduces the possibility of targeted therapy, making these tumors very aggressive with a poor outcome. Cancers are not solely composed of tumor cells, but also include several types of infiltrating cells, such as fibroblasts, macrophages, and other immune cells that have critical functions in regulating cancer cell behaviors. In addition to these cells, the extracellular matrix (ECM) has become an important player in many aspects of breast cancer biology, including cell growth, motility, metabolism, and chemoresistance. Hyaluronan (HA) is a key ECM component that promotes cell proliferation and migration in several malignancies. Notably, HA accumulation in the tumor stroma is a negative prognostic factor in breast cancer. HA metabolism depends on the fine balance between HA synthesis by HA synthases and degradation yielded by hyaluronidases. All the different cell types present in the tumor can release HA in the ECM, and in this review, we will describe the role of HA and HA metabolism in different breast cancer subtypes.

17β-estradiol promotes extracellular vesicle release and selective miRNA loading in ERα-positive breast cancer

The causes and consequences of abnormal biogenesis of extracellular vesicles (EVs) are not yet well understood in malignancies, including in breast cancers (BCs). Given the hormonal signaling dependence of estrogen receptor-positive (ER+) BC, we hypothesized that 17β-estradiol (estrogen) might influence EV production and microRNA (miRNA) loading. We report that physiological doses of 17β-estradiol promote EV secretion specifically from ER+ BC cells via inhibition of miR-149-5p, hindering its regulatory activity on SP1, a transcription factor that regulates the EV biogenesis factor nSMase2. Additionally, miR-149-5p downregulation promotes hnRNPA1 expression, responsible for the loading of let-7's miRNAs into EVs. In multiple patient cohorts, we observed increased levels of let-7a-5p and let-7d-5p in EVs derived from the blood of premenopausal ER+ BC patients, and elevated EV levels in patients with high BMI, both conditions associated with higher levels of 17β-estradiol. In brief, we identified a unique estrogen-driven mechanism by which ER+ BC cells eliminate tumor suppressor miRNAs in EVs, with effects on modulating tumor-associated macrophages in the microenvironment.

Regulation of ERα-dependent breast cancer metastasis by a miR-29a signaling

Malignant breast cancer (BC) remains incurable mainly due to the cancer cell metastasis, which is mostly related to the status of Estrogen receptor alpha (ERα). However, our understanding of the mechanisms through which ERα regulates cancer cell metastasis remains limited. Here we identified a miR-29a-PTEN-AKT axis as a downstream signaling pathway of ERα governing breast cancer progression and metastasis. Two estrogen response element (ERE) half sites were identified in the promoter and enhancer regions of miR-29a, which mediated transcriptional regulation of miR-29a by ERα. Low level of miR-29a showed association with reduced metastasis and better survival in ERα+ luminal subtype of BC. In contrast, high level of miR-29a was detected in ERα- triple negative breast cancer (TNBC) in association with distant metastasis and poor survival. miR-29a overexpression in BC tumors increased the number of circulating tumor cells and promoted lung metastasis in mice. Targeted knockdown of miR-29a in TNBC cells in vitro or administration of a nanotechnology-based anti-miR-29a delivery in TNBC tumor-bearing mice in vivo suppressed cellular invasion, EMT and lung metastasis. PTEN was identified as a direct target of miR-29a, inducing EMT and metastasis via AKT signaling. A small molecular inhibitor of AKT attenuated miR-29a-induced EMT. These findings demonstrate a novel mechanism responsible for ERα-regulated breast cancer metastasis, and reveal the combination of ERα status and miR-29a levels as a new risk indicator in BC.

NFIC1 inhibits the migration and invasion of MDA-MB-231 cells through S100A2-mediated inactivation of MEK/ERK pathway

NFIC is a potent transcriptional factor involved in many physiological and pathological processes, including tumorigenesis. However, the role of NFIC1, the longest isoform of NFIC, in the progression of triple negative breast cancer (TNBC) remains elusive. Our study demonstrates that overexpression of NFIC1 inhibits the migration and invasion of TNBC MDA-MB-231 cells. NFIC1 regulates the expression of S100A2, and knockdown of S100A2 reverses the inhibitive effects of NFIC1 on the migration and invasion of MDA-MB-231 cells. Furthermore, knockdown of S100A2 activates the MEK/ERK signaling transduction pathway that is inhibited by NFIC1 overexperssion. Treatment with MEK/ERK pathway inhibitor, U0126, abolishes the effects of S100A2 knockdown. In addition, overexpression of NFIC1 in MDA-MB-231 cells increases the expression of epithelial markers and decreases the expression of mesenchymal markers, and these effects could also be reversed by knockdown of S100A2. Collectively, these results demonstrate that NFIC1 inhibits the Epithelial-mesenchymal transition (EMT) of MDA-MB-231 cells by regulating S100A2 expression, which suppress the activation of MEK/ERK pathway. Therefore, our study confirms the role of NFIC1 as a tumor repressor in TNBC, and reveals the molecular mechanism through which NFIC1 inhibits the migration and invasion of MDA-MB-231 cells.

Inverse Correlation of KISS1 and KISS1R Expression in Triple-negative Breast Carcinomas from African American Women

BACKGROUND/AIM

The kisspeptin 1 (KISS1) gene encodes a precursor polypeptide which after proteolysis forms the kisspeptin-10 (KISS1) protein. KISS1, retains maximum physiological activity when it binds to its receptor (KISS1R), allowing KISS1 to effectively function as a suppressor of metastasis in melanomas and other types of cancer. The goal of this study was to evaluate the expression of KISS1 and KISS1R in breast carcinomas from African American (AA) women and correlate their association with clinicopathological features, including breast cancer subtypes, and outcomes.

MATERIALS AND METHODS

Tissue microarrays were constructed from formalin-fixed, paraffin-embedded surgical blocks from 216 AA patients. KISS1 and KISS1R expression was assessed using immunohistochemistry. Univariate analysis was used to determine the association between the expression of KISS1 and KISS1R, and clinicopathological characteristics. Pearson correlation was also determined between immunohistochemical H-scores, tumor size, and the number of positive lymph nodes. Kaplan-Meier estimates of overall and disease-free survival were plotted, and log-rank tests were performed to compare estimates among groups.

RESULTS

KISS1 protein expression was found to be higher in receptor-negative and triple-negative breast cancer (TNBC) compared to other subtypes (p<0.001). However, KISS1R expression was higher in non-TNBC tumors compared to other subtypes (p<0.001). Higher KISS1R expression was marginally negatively correlated with tumor size (p=0.077), and positively correlated with lymph-node positivity (p=0.056), and disease-free survival (p=0.092).

CONCLUSION

Our study showed a significant inverse correlation between KISS1 and KISS1R in TNBC. This investigation implicates a role for KISS1 and KISS1R in the pathogenesis of TNBCs in AA women.

microRNA-26b inhibits growth and cellular invasion of ovarian cancer cells by targeting estrogen receptor α

The current study set out to elucidate the mechanism of miR-26b in OC cell proliferation and EMT via suppression of ERα. Initial findings illustrated that miR-26b was poorly expressed in OC tissues and cells. On the other hand, over-expression of miR-26b exerted a diminishing effect on SKOV3 cell proliferation, migration, invasion and EMT, whereas silencing of miR-26b conferred an enhancing effect on CAOV3 cell proliferation, migration, invasion and EMT. Subsequently, with help from the TargetScan database, a dual-luciferase reporter gene assay was carried out to verify the targeting relation between miR-26b and ERα, which revealed that miR-26b could negatively modulate ERα. Furthermore, the in vivo experimentation illustrated that over-expression of miR-26b led to down-regulation of ERα and suppression OC tumor growth and EMT. Meanwhile, silencing of ERα inhibited OC cell proliferation, migration, invasion and EMT. In conclusion, our findings indicated that miR-26b inhibited OC cell proliferation and EMT via negative-modulation of ERα. This investigation may offer potential strategy for OC treatment.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-022-03222-2.

The crucial role of epigenetic regulation in breast cancer anti-estrogen resistance: Current findings and future perspectives

Breast cancer (BC) cell de-sensitization to Tamoxifen (TAM) or other selective estrogen receptor (ER) modulators (SERM) is a complex process associated with BC heterogeneity and the transformation of ER signalling. The most influential resistance-related mechanisms include modifications in ER expression and gene regulation patterns. During TAM/SERM treatment, epigenetic mechanisms can effectively silence ER expression and facilitate the development of endocrine resistance. ER status is efficiently regulated by specific epigenetic tools including hypermethylation of CpG islands within ER promoters, increased histone deacetylase activity in the ER promoter, and/or translational repression by miRNAs. Over-methylation of the ER α gene (ESR1) promoter by DNA methyltransferases was associated with poor prognosis and indicated the development of resistance. Moreover, BC progression and spreading were marked by transformed chromatin remodelling, post-translational histone modifications, and expression of specific miRNAs and/or long non-coding RNAs. Therefore, targeted inhibition of histone acetyltransferases (e.g. MYST3), deacetylases (e.g. HDAC1), and/or demethylases (e.g. lysine-specific demethylase LSD1) was shown to recover and increase BC sensitivity to anti-estrogens. Indicated as a powerful molecular instrument, the administration of epigenetic drugs can regain ER expression along with the activation of tumour suppressor genes, which can in turn prevent selection of resistant cells and cancer stem cell survival. This review examines recent advances in the epigenetic regulation of endocrine drug resistance and evaluates novel anti-resistance strategies. Underlying molecular mechanisms of epigenetic regulation will be discussed, emphasising the utilization of epigenetic enzymes and their inhibitors to re-program irresponsive BCs.

Estrogen Receptor-Regulated Gene Signatures in Invasive Breast Cancer Cells and Aggressive Breast Tumors

Most metastatic breast cancers arise from estrogen receptor α (ER)-positive disease, and yet the role of ER in promoting metastasis is unclear. Here, we used an ER+ breast cancer cell line that is highly invasive in an ER- and IKKβ-dependent manner. We defined two ER-regulated gene signatures that are specifically regulated in the subpopulations of invasive cells. The first consists of proliferation-associated genes, which is a known function of ER, which actually suppress rather than enhance invasion. The second signature consists of genes involved in essential biological processes, such as organelle assembly and vesicle trafficking. Importantly, the second subpopulation-specific signature is associated with aggressive disease and poor patient outcome, independently of proliferation. These findings indicate a complex interplay between ER-driven proliferation and invasion, and they define new ER-regulated gene signatures that are predictive of aggressive ER+ breast cancer.

TGFα-EGFR pathway in breast carcinogenesis, association with WWOX expression and estrogen activation

WWOX is a tumor-suppressive steroid dehydrogenase, which relationship with hormone receptors was shown both in animal models and breast cancer patients. Herein, through nAnT-iCAGE high-throughput gene expression profiling, we studied the interplay of estrogen receptors and the WWOX in breast cancer cell lines (MCF7, T47D, MDA-MB-231, BT20) under estrogen stimulation and either introduction of the WWOX gene by retroviral transfection (MDA-MB-231, T47D) or silenced with shRNA (MCF7, BT20). Additionally, we evaluated the consequent biological characteristics by proliferation, apoptosis, invasion, and adhesion assays. TGFα-EGFR signaling was found to be significantly affected in all examined breast cancer cell lines in response to estrogen and strongly associated with the level of WWOX expression, especially in ER-positive MCF7 cells. Under the influence of 17β-estradiol presence, biological characteristics of the cell lines were also delineated. The study revealed modulation of adhesion, invasion, and apoptosis. The obtained results point at a complex role of the WWOX gene in the carcinogenesis of the breast tissue, which seems to be closely related to the presence of estrogen α and/or β receptors.

Tumor Budding in Gynecologic Cancer as a Marker for Poor Survival: A Systematic Review and Meta-Analysis of the Perspectives of Epithelial-Mesenchymal Transition

This study aimed to assess the prognostic significance, assessment methods, and molecular features of tumor budding (TB). A literature search of Medline, EMBASE, Cochrane Library, and eleven cohort studies (seven cervical and four endometrial cancers) was conducted. Three assessment methods for TB involving 2009 patients were collected and constituted in the analysis. Our meta-analysis showed that TB was a marker of poor survival, regardless of the cancer origin site or assessment method (overall survival: hazard ratio [HR], 2.40; 95% confidence interval [CI], 1.82-3.17; disease-free survival: HR, 3.32; 95% CI, 2.46-4.48). In endometrial cancers, TB is associated with the epithelial-mesenchymal transition, microvessel density, and decreased hormone receptor expression. Thus, we suggest TB as a poor prognostic marker for all gynecologic cancers.

Multifaceted Interplay between Hormones, Growth Factors and Hypoxia in the Tumor Microenvironment

Hormones and growth factors (GFs) are signaling molecules implicated in the regulation of a variety of cellular processes. They play important roles in both healthy and tumor cells, where they function by binding to specific receptors on target cells and activating downstream signaling cascades. The stages of tumor progression are influenced by hormones and GF signaling. Hypoxia, a hallmark of cancer progression, contributes to tumor plasticity and heterogeneity. Most solid tumors contain a hypoxic core due to rapid cellular proliferation that outgrows the blood supply. In these circumstances, hypoxia-inducible factors (HIFs) play a central role in the adaptation of tumor cells to their new environment, dramatically reshaping their transcriptional profile. HIF signaling is modulated by a variety of factors including hormones and GFs, which activate signaling pathways that enhance tumor growth and metastatic potential and impair responses to therapy. In this review, we summarize the role of hormones and GFs during cancer onset and progression with a particular focus on hypoxia and the interplay with HIF proteins. We also discuss how hypoxia influences the efficacy of cancer immunotherapy, considering that a hypoxic environment may act as a determinant of the immune-excluded phenotype and a major hindrance to the success of adoptive cell therapies.

Prolactin: The Third Hormone in Breast Cancer

Prolactin coordinates with the ovarian steroids to orchestrate mammary development and lactation, culminating in nourishment and an increasingly appreciated array of other benefits for neonates. Its central activities in mammary epithelial growth and differentiation suggest that it plays a role(s) in breast cancer, but it has been challenging to identify its contributions, essential for incorporation into prevention and treatment approaches. Large prospective epidemiologic studies have linked higher prolactin exposure to increased risk, particularly for ER+ breast cancer in postmenopausal women. However, it has been more difficult to determine its actions and clinical consequences in established tumors. Here we review experimental data implicating multiple mechanisms by which prolactin may increase the risk of breast cancer. We then consider the evidence for role(s) of prolactin and its downstream signaling cascades in disease progression and treatment responses, and discuss how new approaches are beginning to illuminate the biology behind the seemingly conflicting epidemiologic and experimental studies of prolactin actions across diverse breast cancers.

Natural and Synthetic Estrogens in Chronic Inflammation and Breast Cancer

The oncogenic role of estrogen receptor (ER) signaling in breast cancer has long been established. Interaction of estrogen with estrogen receptor (ER) in the nucleus activates genomic pathways of estrogen signaling. In contrast, estrogen interaction with the cell membrane-bound G-protein-coupled estrogen receptor (GPER) activates the rapid receptor-mediated signaling transduction cascades. Aberrant estrogen signaling enhances mammary epithelial cell proliferation, survival, and angiogenesis, hence is an important step towards breast cancer initiation and progression. Meanwhile, a growing number of studies also provide evidence for estrogen's pro- or anti-inflammatory roles. As other articles in this issue cover classic ER and GPER signaling mediated by estrogen, this review will discuss the crucial mechanisms by which estrogen signaling influences chronic inflammation and how that is involved in breast cancer. Xenoestrogens acquired from plant diet or exposure to industrial products constantly interact with and alter innate estrogen signaling at various levels. As such, they can modulate chronic inflammation and breast cancer development. Natural xenoestrogens generally have anti-inflammatory properties, which is consistent with their chemoprotective role in breast cancer. In contrast, synthetic xenoestrogens are proinflammatory and carcinogenic compounds that can increase the risk of breast cancer. This article also highlights important xenoestrogens with a particular focus on their role in inflammation and breast cancer. Improved understanding of the complex relationship between estrogens, inflammation, and breast cancer will guide clinical research on agents that could advance breast cancer prevention and therapy.

E239K mutation abolishes the suppressive effects of lysine-specific demethylase 1 on migration and invasion of MCF7 cells

Lysine‐specific demethylase 1 (LSD1) is an important histone demethylase that mediates epithelial to mesenchymal transition (EMT). The E239K mutation of LSD1 was identified in a luminal breast cancer patient from the COSMIC Breast Cancer dataset. To investigate the functional effects of the E239K mutation of LSD1, a stable LSD1 knockdown MCF7 cell line was generated. Rescue with WT LSD1, but not E239K mutated LSD1, suppressed the invasion and migration of the LSD1 knockdown cells, indicating that the E239K mutation abolished the suppressive effects of LSD1 on the invasion and migration of MCF7 cells. Further analysis showed that the E239K mutation abolished LSD1‐mediated invasion and migration of MCF7 cells through downregulation of estrogen receptor α (ERα). Most importantly, the E239K mutation disrupted the interaction between LSD1 and GATA3, which reduced the enrichment of LSD1 at the promoter region of the ERα gene; the reduced enrichment of LSD1 at the promoter region of the ERα gene caused enhanced histone H3K9 methylation, which subsequently suppressed the transcription of the ERα gene. In summary, the E239K mutation abolishes the suppressive function of LSD1 on migration and invasion of breast cancer cells by disrupting the interaction between LSD1 and GATA3.

Endogenous and Therapeutic Estrogens: Maestro Conductors of the Microenvironment of ER+ Breast Cancers

Estrogen receptor alpha (ERα) marks heterogeneous breast cancers which display a repertoire of somatic genomic mutations and an immune environment that differs from other breast cancer subtypes. These cancers also exhibit distinct biological behaviors; despite an overall better prognosis than HER2+ or triple negative breast cancers, disseminated dormant cells can lead to disease recurrence decades after the initial diagnosis and treatment. Estrogen is the best studied driver of these cancers, and antagonism or reduction of estrogen activity is the cornerstone of therapeutic approaches. In addition to reducing proliferation of ERα+ cancer cells, these treatments also alter signals to multiple other target cells in the environment, including immune cell subpopulations, cancer-associated fibroblasts, and endothelial cells via several distinct estrogen receptors. In this review, we update progress in our understanding of the stromal cells populating the microenvironments of primary and metastatic ER+ tumors, the effects of estrogen on tumor and stromal cells to modulate immune activity and the extracellular matrix, and net outcomes in experimental and clinical studies. We highlight new approaches that will illuminate the unique biology of these cancers, provide the foundation for developing new treatment and prevention strategies, and reduce mortality of this disease.

Role of organophosphorous pesticides and acetylcholine in breast carcinogenesis

Breast cancer is the leading cause of cancer-related death in women worldwide. Several studies have addressed the association between cancer in humans and agricultural pesticide exposure. Evidence indicates that exposure to organophosphorous pesticides such as parathion and malathion occurs as a result of occupational factors since they are extensively used to control insects. On the other hand, estrogens have been considered beneficial to the organism; however, epidemiological studies have pointed out an increased breast cancer risk in both humans and animals. Experimental female rat mammary gland cancer models were developed after exposure to parathion, malathion, eserine, an acetylcholinesterase inhibitor, and estrogen allowing the analysis of the signs of carcinogenicity as alteration of cell proliferation, receptor expression, genomic instability, and cell metabolism in vivo and in vitro. Thus, pesticides increased proliferative ducts followed by ductal carcinoma; and 17β-estradiol increased proliferative lobules followed by lobular carcinomas. The combination of both pesticides and either eserine or estrogen induced tumors with both types of structures followed by mammary gland tumors and metastasis to the lung and kidneys after 240 days of a 5-day treatment. Studies also showed that these pesticides and eserine decreased three to five times the acetylcholinesterase activity in the serum compared to controls whereas terminal end buds increased in number, being inhibited by atropine. Genomic instability was analyzed in such tissues (mp53, CYP1A2, c-myc, c-fos, ERα, M2R) and pesticides increased protein expression that was stimulated by estrogens but inhibited by atropine. Eserine also transformed the epithelium of the rat mammary gland in the presence of estrogen and increased the number of terminal end buds after treatment inducing mammary carcinomas. Then, enzymatic digestion of such structures gave rise to cells with increased DNA synthesis and induced anchorage independence. Thus, there were changes in the epithelium of the mammary gland influencing breast carcinogenesis. Furthermore, these substances and acetylcholine also showed the signs of carcinogenicity in vitro as cell proliferation, receptor expression (ERα, ErbB2, M2R), genomic instability (c-myc, mp53, ERα, M2R), and cell metabolism. A unique cellular model is also presented here based on the use of MCF-10 F, a non-tumorigenic cell line that represents a valuable clinically translatable experimental approach that identifies mechanistic links for pesticides and estrogen as suspect human carcinogenic agents.

miRNA Expression Profiles in Luminal A Breast Cancer-Implications in Biology, Prognosis, and Prediction of Response to Hormonal Treatment

Breast cancer, which is the most common malignancy in women, does not form a uniform nosological unit but represents a group of malignant diseases with specific clinical, histopathological, and molecular characteristics. The increasing knowledge of the complex pathophysiological web of processes connected with breast cancercarcinogenesis allows the development of predictive and prognostic gene expressionand molecular classification systems with improved risk assessment, which could be used for individualized treatment. In our review article, we present the up-to-date knowledge about the role of miRNAs and their prognostic and predictive value in luminal A breast cancer. Indeed, an altered expression profile of miRNAs can distinguish not only between cancer and healthy samples, but they can classify specific molecular subtypes of breast cancer including HER2, Luminal A, Luminal B, and TNBC. Early identification and classification of breast cancer subtypes using miRNA expression profilescharacterize a promising approach in the field of personalized medicine. A detection of sensitive and specific biomarkers to distinguish between healthy and early breast cancer patients can be achieved by an evaluation of the different expression of several miRNAs. Consequently, miRNAs represent a potential as good diagnostic, prognostic, predictive, and therapeutic biomarkers for patients with luminal A in the early stage of BC.

Role of microRNA/Epithelial-to-Mesenchymal Transition Axis in the Metastasis of Bladder Cancer

Bladder cancer (BC) is the 11th most common diagnosed cancer, and a number of factors including environmental and genetic ones participate in BC development. Metastasis of BC cells into neighboring and distant tissues significantly reduces overall survival of patients with this life-threatening disorder. Recently, studies have focused on revealing molecular pathways involved in metastasis of BC cells, and in this review, we focus on microRNAs (miRNAs) and their regulatory effect on epithelial-to-mesenchymal transition (EMT) mechanisms that can regulate metastasis. EMT is a vital process for migration of BC cells, and inhibition of this mechanism restricts invasion of BC cells. MiRNAs are endogenous non-coding RNAs with 19-24 nucleotides capable of regulating different cellular events, and EMT is one of them. In BC cells, miRNAs are able to both induce and/or inhibit EMT. For regulation of EMT, miRNAs affect different molecular pathways such as transforming growth factor-beta (TGF-β), Snail, Slug, ZEB1/2, CD44, NSBP1, which are, discussed in detail this review. Besides, miRNA/EMT axis can also be regulated by upstream mediators such as lncRNAs, circRNAs and targeted by diverse anti-tumor agents. These topics are also discussed here to reveal diverse molecular pathways involved in migration of BC cells and strategies to target them to develop effective therapeutics.

Epigenetics of Estrogen and Progesterone Receptors in Endometriosis

Endometriosis is an estrogen-dependent inflammatory gynecological disease. Increased estrogen activity and progesterone resistance are the main hormonal substrate of this disease and are associated with inflammatory response and debilitating symptoms, including pain and infertility. Estrogens and progesterone act via their specific nuclear receptors. The regulation of receptor expression by epigenetics maybe a critical factor for endometriosis. The present review aims to discuss the epigenetic mechanisms related to the expression of estrogen receptors (ERs) and progesterone receptors (PRs) in patients with endometriosis, including two classic epigenetic mechanisms: DNA methylation and histone modification, and, other non-classic mechanisms: miRNAs and lncRNA. Several in vitro and in vivo studies support the key role of epigenetics in the regulation of the expression of ERs and PRs, which may provide new molecules and targets for the diagnosis and treatment of endometriosis.

Clinical association of progesterone receptor isoform A with breast cancer metastasis consistent with its unique mechanistic role in preclinical models

Background

Luminal breast cancer (L-BCa) comprises the majority of incurable, distally metastatic breast cancer cases. Estrogen supports growth of L-BCa cells but suppresses invasiveness. Estrogen also induces the progesterone receptor (PR). Invasiveness and metastasis of L-BCa cells is supported by the short PR isoform (PR-A), in response to the range of pre- and post-menopausal plasma hormone levels, by counteracting the effects of estrogen via micro RNA-mediated cross-talk with the estrogen receptor (ER). PR-B directly supports L-BCa invasion and metastasis and also inhibits tumor growth, both only at high progesterone levels. As public datasets on L-BCa tumors cannot distinguish PR-A, this study was designed to seek clinical evidence for the role of PR-A in metastasis in comparison with PR-B and ER.

Methods

Measurement of tumor PR-A, PR-B and ER mRNA expression in 125 treatment-naive primary L-BCa patients with differential node involvement and analysis using linear mixed effects models. Transcriptional activity assays of PR-A and PR-B.

Results

Lymph node involvement was strongly associated with PR-A expression (median, 3-fold higher vs. node-negative), independent of age, pathologic type, tumor grade, HER2 and PR-B. PR-B and ER correlated weakly with PR-A, but whereas PR-B and the PR-A/PR-B ratio were not significantly associated with node involvement, ER weakly negatively correlated with node positivity. PR-A was hypersensitive to mifepristone compared with PR-B.

Conclusions

Taken together with previous mechanistic studies, the findings provide clinical evidence in support of the role of PR-A in L-BCa metastasis. They also suggest the possibility of developing selective PR-A modulators for future interventions in appropriate clinical situations.

A Truncated Snail1 Transcription Factor Alters the Expression of Essential EMT Markers and Suppresses Tumor Cell Migration in a Human Lung Cancer Cell Line

BACKGROUND

Epithelial-to-Mesenchymal Transition (EMT) is necessary for metastasis. Zinc- finger domain-containing transcription factors, especially Snail1, bind to E-box motifs and play a crucial role in the induction and regulation of EMT.

OBJECTIVE

We hypothesized if C-terminal region of Snail1 (CSnail1) may competitively bind to E-box and block cancer metastasis.

METHODS

The CSnail1 gene coding sequence was inserted into the pIRES2-EGFP vector. Following transfection of A549 cells with the designed construct, EMT was induced with TGF-β1 and the expression of essential EMT markers was evaluated by real-time PCR and immunoblotting. We also monitored cell migration.

RESULTS

CSnail1 inhibited TGF-β1-induced N-cadherin and vimentin mRNA expression and increased β-catenin expression in transfected TGF-β1-treated A549 cells. A similar finding was obtained in western blotting. CSnail1 also blocked the migration of transfected cells in the scratch test.

CONCLUSION

Transfection of A549 cells with CSnail1 alters the expression of essential EMT markers and consequently suppresses tumor cell migration. These findings confirm the capability of CSnail1 in EMT blocking and in parallel to current patents could be applied as a novel strategy in the prevention of metastasis.

miR-200 affects tamoxifen resistance in breast cancer cells through regulation of MYB

Resistance to tamoxifen is a major clinical challenge. Research in recent years has identified epigenetic changes as mediated by dysregulated miRNAs that can possibly play a role in resistance to tamoxifen in breast cancer patients expressing estrogen receptor (ER). We report here elevated levels of EMT markers (vimentin and ZEB1/2) and reduced levels of EMT-regulating miR-200 (miR-200b and miR-200c) in ER-positive breast cancer cells, MCF-7, that were resistant to tamoxifen, in contrast with the naïve parental MCF-7 cells that were sensitive to tamoxifen. Further, we established regulation of c-MYB by miR-200 in our experimental model. C-MYB was up-regulated in tamoxifen resistant cells and its silencing significantly decreased resistance to tamoxifen and the EMT markers. Forced over-expression of miR-200b/c reduced c-MYB whereas reduced expression of miR-200b/c resulted in increased c-MYB We further confirmed the results in other ER-positive breast cancer cells T47D cells where forced over-expression of c-MYB resulted in induction of EMT and significantly increased resistance to tamoxifen. Thus, we identify a novel mechanism of tamoxifen resistance in breast tumor microenvironment that involves miR-200-MYB signaling.

Connecting sex differences, estrogen signaling, and microRNAs in cardiac fibrosis

Sex differences are evident in the pathophysiology of heart failure (HF). Progression of HF is promoted by cardiac fibrosis and no fibrosis-specific therapies are currently available. The fibrotic response is mediated by cardiac fibroblasts (CFs), and a central event is their phenotypic transition to pro-fibrotic myofibroblasts. These myofibroblasts may arise from various cellular origins including resident CFs and epicardial and endothelial cells. Both female subjects in clinical studies and female animals in experimental studies generally present less cardiac fibrosis compared with males. This difference is at least partially considered attributable to the ovarian hormone 17β-estradiol (E2). E2 signals via estrogen receptors to regulate genes are involved in the fibrotic response and myofibroblast transition. Besides protein-coding genes, E2 also regulates transcription of microRNA that modulate cardiac fibrosis. Sex dimorphism, E2, and miRNAs form multi-level regulatory networks in the pathophysiology of cardiac fibrosis, and the mechanism of these networks is not yet fully deciphered. Therefore, this review is aimed at summarizing current knowledge on sex differences, E2, and estrogen receptors in cardiac fibrosis, emphasizing on microRNAs and myofibroblast origins. KEY MESSAGES: • E2 and ERs regulate cardiac fibroblast function. • E2 and ERs may distinctly affect male and female cardiac fibrosis pathophysiology. • Sex, E2, and miRNAs form multi-level regulatory networks in cardiac fibrosis. • Sex-dimorphic and E2-regulated miRNAs affect mesenchymal transition.

[Medium-chain acyl-CoA dehydrogenase enhances invasion and metastasis ability of breast cancer cells]

OBJECTIVE

To investigate the effect of medium-chain acyl-CoA dehydrogenase (ACADM) on invasion and metastasis of breast cancer cells and explore the underlying mechanism.

METHODS

A large cancer genome database was used to analyze the expression of ACADM in breast cancer tissues and normal tissues. The proliferation, migration and invasion of cultured breast cancer MCF-7 and T47D cells with ACADM overexpression or ACADM silencing were evaluated using MTT proliferation assay, EdU assay, Transwell chamber assay, and Boyden invasion assay; Western blotting was used to detect the protein expressions of the related pathway in the cells. In nude mouse models of tail vein metastasis of MCF-7 cells with or without ACADM overexpression, the tumor growth and tumor histopathology were observed using HE staining.

RESULTS

Analysis of the Oncomine sample set showed a significantly higher expression level of ACADM in breast cancer tissues than in normal breast tissues (P &lt; 0.05). Overexpression of ACADM obviously enhanced the migration and invasion abilities and promoted the epithelial-mesenchymal transition (EMT) of cultured MCF-7 and T47D cells; conversely, silencing of ACADM significantly suppressed the migration and invasion of the breast cancer cells. In the nude mouse models, ACADM overexpression in MCF-7 cells significantly enhanced their in vivo migration and invasion abilities.

CONCLUSIONS

ACADM can promote the EMT process of breast cancer cells and improve the migration and invasion ability. ACADM is an oncogene in breast cancer.

Epigenetic inactivation of miR-203 as a key step in neural crest epithelial-to-mesenchymal transition

miR-203 is a tumor-suppressor microRNA with known functions in cancer metastasis. Here, we explore its normal developmental role in the context of neural crest development. During the epithelial-to-mesenchymal transition of neural crest cells to emigrate from the neural tube, miR-203 displays a reciprocal expression pattern with key regulators of neural crest delamination, Phf12 and Snail2, and interacts with their 3'UTRs. We show that ectopic maintenance of miR-203 inhibits neural crest migration in chick, whereas its functional inhibition using a 'sponge' vector or morpholinos promotes premature neural crest delamination. Bisulfite sequencing further shows that epigenetic repression of miR-203 is mediated by the de novo DNA methyltransferase DNMT3B, the recruitment of which to regulatory regions on the miR-203 locus is directed by SNAIL2 in a negative-feedback loop. These findings reveal an important role for miR-203 in an epigenetic-microRNA regulatory network that influences the timing of neural crest delamination.

Higher order genomic organization and epigenetic control maintain cellular identity and prevent breast cancer

Cells establish and sustain structural and functional integrity of the genome to support cellular identity and prevent malignant transformation. In this review, we present a strategic overview of epigenetic regulatory mechanisms including histone modifications and higher order chromatin organization (HCO) that are perturbed in breast cancer onset and progression. Implications for dysfunctions that occur in hormone regulation, cell cycle control, and mitotic bookmarking in breast cancer are considered, with an emphasis on epithelial-to-mesenchymal transition and cancer stem cell activities. The architectural organization of regulatory machinery is addressed within the contexts of translating cancer-compromised genomic organization to advances in breast cancer risk assessment, diagnosis, prognosis, and identification of novel therapeutic targets with high specificity and minimal off target effects.

Increase in hyaluronic acid degradation decreases the expression of estrogen receptor alpha in MCF7 breast cancer cell line

The loss of estrogen receptor α (ERα) expression in breast cancer constitutes a major hallmark of tumor progression to metastasis and is generally correlated to a strong increase in Hyaluronic Acid (HA) turnover. The aim of our study was to search for a putative link between these two major events of breast cancer progression in the estrogen receptor-positive (ER+) MCF7 breast cancer cell line. The increase in HA turnover was performed by stable overexpression of the standard CD44 (CD44S) isoform and also by treatment with exogenous Hyaluronidase (Hyal) to allow an increase in HA catabolism. Stable overexpression of CD44S in MCF7 cells was correlated to a decrease in ESR1 gene expression, which did not lead to alteration of estrogen response. Moreover, our results showed that the exposure to exogenous Hyal stimulates the proliferation and strongly decreases the expression of ERα whatever the expression level of CD44 in the MCF7 cell line. The culture in the presence of Hyal led to the decrease in estrogens responsiveness and to hormonal therapy resistance. The effect on growth is correlated to the activation of MAPK/ERK and PI3K/Akt signaling pathways while the Hyal-induced down-regulation of ESR1 gene expression involves the activation of PI3K/Akt and NF-κB signaling pathways. Many of our data suggest that the effects of Hyal described here could be related to the activation of TLR signaling. Taken together, our results demonstrate that the increase in HA degradation could be involved in breast cancer progression and in resistance to hormonal therapy.

Estrogen Regulation of T-Cell Function and Its Impact on the Tumor Microenvironment

Epidemiologic studies demonstrate significant gender-specific differences in immune system function. Males are more prone to infection and malignancies, while females are more vulnerable to autoimmune diseases. These differences are thought to be due to the action of gonadal hormones: Estrogen increases the inflammatory response and testosterone dampens it. More specifically, estrogen stimulation induces inflammatory cytokine production including interferon γ, interleukin (IL) 6, and tumor necrosis factor α, while testosterone induces IL-10, IL-4, and transforming growth factor β. More recent studies demonstrate threshold effects of estrogen stimulation on immune cell function: physiologic doses of estrogen (approximately 0.5 nmol/L) stimulate inflammatory cytokine production, but superphysiologic dosages (above 50 nmol/L) can result in decreased inflammatory cytokine production. This review reports findings concerning the impact of estrogen on CD8+ cytotoxic T cells and the overall immune response in the tumor microenvironment. Variables examined include dosage of hormone, the diversity of immune cells involved, and the nature of the immune response in cancer. Collective review of these points may assist in future hypotheses and studies to determine sex-specific differences in immune responses that may be used as targets in disease prevention and treatment.

Mechanisms for estrogen receptor expression in human cancer

Estrogen is a steroid hormone that has critical roles in reproductive development, bone homeostasis, cardiovascular remodeling and brain functions. However, estrogen also promotes mammary, ovarian and endometrial tumorigenesis. Estrogen antagonists and drugs that reduce estrogen biosynthesis have become highly successful therapeutic agents for breast cancer patients. The effects of estrogen are largely mediated by estrogen receptor (ER) α and ERβ, which are members of the nuclear receptor superfamily of transcription factors. The mechanisms underlying the aberrant expression of ER in breast cancer and other types of human tumors are complex, involving considerable alternative splicing of ERα and ERβ, transcription factors, epigenetic and post-transcriptional regulation of ER expression. Elucidation of mechanisms for ER expression may not only help understand cancer progression and evolution, but also shed light on overcoming endocrine therapy resistance. Herein, we review the complex mechanisms for regulating ER expression in human cancer.

Transforming growth factor beta1 targets estrogen receptor signaling in bronchial epithelial cells

Background

Sex differences in idiopathic pulmonary fibrosis (IPF) suggest a protective role for estrogen (E2); however, mechanistic studies in animal models have produced mixed results. Reports using cell lines have investigated molecular interactions between transforming growth factor beta1 (TGF-β1) and estrogen receptor (ESR) pathways in breast, prostate, and skin cells, but no such interactions have been described in human lung cells. To address this gap in the literature, we investigated a role for E2 in modulating TGF-β1-induced signaling mechanisms and identified novel pathways impacted by estrogen in bronchial epithelial cells.

Methods

We investigated a role for E2 in modulating TGF-β1-induced epithelial to mesenchymal transition (EMT) in bronchial epithelial cells (BEAS-2Bs) and characterized the effect of TGF-β1 on ESR mRNA and protein expression in BEAS-2Bs. We also quantified mRNA expression of ESRs in lung tissue from individuals with IPF and identified potential downstream targets of E2 signaling in BEAS-2Bs using RNA-Seq and gene set enrichment analysis.

Results

E2 negligibly modulated TGF-β1-induced EMT; however, we report the novel observation that TGF-β1 repressed ESR expression, most notably estrogen receptor alpha (ESR1). Results of the RNA-Seq analysis showed that TGF-β1 and E2 inversely modulated the expression of several genes involved in processes such as extracellular matrix (ECM) turnover, airway smooth muscle cell contraction, and calcium flux regulation. We also report that E2 specifically modulated the expression of genes involved in chromatin remodeling pathways and that this regulation was absent in the presence of TGF-β1.

Conclusions

Collectively, these results suggest that E2 influences unexplored pathways that may be relevant to pulmonary disease and highlights potential roles for E2 in the lung that may contribute to sex-specific differences.

Electronic supplementary material

The online version of this article (10.1186/s12931-018-0861-5) contains supplementary material, which is available to authorized users.

Role of p38γ MAPK in regulation of EMT and cancer stem cells

p38γ is a member of p38 MAPK family which contains four isoforms p38α, p38β, p38γ, and p38δ. p38γ MAPK has unique function and is less investigated. Recent studies revealed that p38γ MAPK may be involved in tumorigenesis and cancer aggressiveness. However, the underlying cellular/molecular mechanisms remain unclear. Epithelial-mesenchymal transition (EMT) is a process that epithelial cancer cells transform to facilitate the loss of epithelial features and gain of mesenchymal phenotype. EMT promotes cancer cell progression and metastasis, and is involved in the regulation of cancer stem cells (CSCs) which have self-renewal capacity and are resistant to chemotherapy and target therapy. We showed that p38γ MAPK significantly increased EMT in breast cancer cells; over-expression of p38γ MAPK enhanced EMT while its down-regulation inhibited EMT. Meanwhile, p38γ MAPK augmented CSC population while knock down of p38γ MAPK decreased CSC ratio in breast cancer cells. MicroRNA-200b (miR-200b) was down-stream of p38γ MAPK and inhibited by p38γ MAPK; miR-200b mimics blocked p38γ MAPK-induced EMT while miR-200b inhibitors promoted EMT. p38γ MAPK regulated miR-200b through inhibiting GATA3. p38γ MAPK induced GATA3 ubiquitination, leading to its proteasome-dependent degradation. Suz12, a Polycomb group protein, was down-stream of miR-200b and involved in miR-200b regulation of EMT. Thus, our study established an important role of p38γ MAPK in EMT and identified a novel signaling pathway for p38γ MAPK-mediated tumor promotion.

Notch3 inhibits epithelial-mesenchymal transition in breast cancer via a novel mechanism, upregulation of GATA-3 expression

Notch3 and GATA binding protein 3 (GATA-3) have been, individually, shown to maintain luminal phenotype and inhibit epithelial-mesenchymal transition (EMT) in breast cancers. In the present study, we report that Notch3 expression positively correlates with that of GATA-3, and both are associated with estrogen receptor-α (ERα) expression in breast cancer cells. We demonstrate in vitro and in vivo that Notch3 suppressed EMT and breast cancer metastasis by activating GATA-3 transcription. Furthermore, Notch3 knockdown downregulated GATA-3 and promoted EMT; while overexpression of Notch3 intracellular domain upregulated GATA-3 and inhibited EMT, leading to a suppression of metastasis in vivo. Moreover, inhibition or overexpression of GATA-3 partially reversed EMT or mesenchymal-epithelial transition induced by Notch3 alterations. In breast cancer patients, high GATA-3 expression is associated with higher Notch3 expression and lower lymph node metastasis, especially for hormone receptor (HR) positive cancers. Herein, we demonstrate a novel mechanism whereby Notch3 inhibit EMT by transcriptionally upregulating GATA-3 expression, at least in part, leading to the suppression of cancer metastasis in breast cancers. Our findings expand our current knowledge on Notch3 and GATA-3's roles in breast cancer metastasis.

Estrogen promotes estrogen receptor negative BRCA1-deficient tumor initiation and progression

BACKGROUND

Estrogen promotes breast cancer development and progression mainly through estrogen receptor (ER). However, blockage of estrogen production or action prevents development of and suppresses progression of ER-negative breast cancers. How estrogen promotes ER-negative breast cancer development and progression is poorly understood. We previously discovered that deletion of cell cycle inhibitors p16Ink4a (p16) or p18Ink4c (p18) is required for development of Brca1-deficient basal-like mammary tumors, and that mice lacking p18 develop luminal-type mammary tumors.

METHODS

A genetic model system with three mouse strains, one that develops ER-positive mammary tumors (p18 single deletion) and the others that develop ER-negative tumors (p16;Brca1 and p18;Brca1 compound deletion), human BRCA1 mutant breast cancer patient-derived xenografts, and human BRCA1-deficient and BRCA1-proficient breast cancer cells were used to determine the role of estrogen in activating epithelial-mesenchymal transition (EMT), stimulating cell proliferation, and promoting ER-negative mammary tumor initiation and metastasis.

RESULTS

Estrogen stimulated the proliferation and tumor-initiating potential of both ER-positive Brca1-proficient and ER-negative Brca1-deficient tumor cells. Estrogen activated EMT in a subset of Brca1-deficient mammary tumor cells that maintained epithelial features, and enhanced the number of cancer stem cells, promoting tumor progression and metastasis. Estrogen activated EMT independent of ER in Brca1-deficient, but not Brca1-proficient, tumor cells. Estrogen activated the AKT pathway in BRCA1-deficient tumor cells independent of ER, and pharmaceutical inhibition of AKT activity suppressed EMT and cell proliferation preventing BRCA1 deficient tumor progression.

CONCLUSIONS

This study reveals for the first time that estrogen promotes BRCA1-deficient tumor initiation and progression by stimulation of cell proliferation and activation of EMT, which are dependent on AKT activation and independent of ER.

Progesterone receptor A promotes invasiveness and metastasis of luminal breast cancer by suppressing regulation of critical microRNAs by estrogen

Distal metastasis of luminal breast cancer is frequent and incurable, yet the metastasis mechanisms are poorly understood. Estrogen, even at postmenopausal concentrations, suppresses invasiveness of luminal breast cancer cells through the estrogen receptor (ER). Invasive tumors overexpress the short progesterone receptor A (PR-A) isoform. Even at postmenopausal concentrations, progesterone activates PR-A, inducing invasiveness by counteracting estrogen's effects, particularly when cells are hypersensitized to progesterone by PR-A overexpression. To interrogate the role of this cross-talk in metastasis, we investigated selective cross-talk mechanisms of PR-A with ER. We developed a quantitative PCR-based lymph node infiltration assay to address the slowness of metastasis of tumor xenografts. We found that 15 microRNAs (miRNAs) are regulated by progesterone via PR-A, but not the longer PR-B isoform, with increased progesterone sensitivity when PR-A was overexpressed. Two of these miRNAs whose induction (miR-92a-3p) or repression (miR-26b-5p) by estrogen was suppressed by progesterone plus PR-A were critical for the PR-A-ER cross-talk causing a gene-regulatory pattern of invasiveness and metastasis and complete rescue of invasiveness in vitro Constitutive expression of miR-92a-3p or inhibition of miR-26b-5p profoundly suppressed metastasis. Finally, in primary breast tumors, PR-A expression was correlated negatively with miR-92a-3p expression and positively with miR-26b-5p expression. Therefore, hormonal cross-talk of PR-A with ER is probably a fundamental mechanism that enables metastasis of luminal breast cancer. Moreover, miRNA biomarkers of hyperactive PR-A may help predict metastatic potential of luminal breast tumors. Further, miR-92a-3p and miR-26b-5p may reveal target pathways for selective intervention to suppress hormone-regulated metastasis, both pre- and postmenopause.

Estradiol promotes epithelial-to-mesenchymal transition in human benign prostatic epithelial cells

BACKGROUND

Epithelial-to-mesenchymal transition (EMT) is involved in pathogenesis of human benign prostatic hyperplasia (BPH). Estrogenic signaling pathways may stimulate the induction of EMT. However, the details of estradiol (E2) and estrogen receptors (ERs) effects on EMT, as well as E2-induced modulation of benign prostatic epithelial cell phenotype in vitro have not been completely clarified.

METHODS

The effects of E2 on EMT markers and cytokeratins (CKs) expression were evaluated in benign epithelial cell lines BPH-1 and RWPE-1, which were cultured both in two-dimensional (2D) culture and three-dimensional (3D) culture model using hanging drop technique or 3D Matrigel model. ER antagonist, ICI182,780, was used to confirm the regulatory effects of E2 on EMT and phenotypic modulation. In 3D culture, immunohistochemical stainings were performed to detect the specific phenotype of cells that underwent EMT in acinar-like spheroids formed by RWPE-1. To illustrate the exact function of ERs in E2-induced EMT and phenotypic modulation, specific short interfering RNAs (siRNAs), and agonists were used to knockdown or activate individual ERs, respectively.

RESULTS

E2-induced EMT was observed both in 2D and 3D culture, with related regulation of EMT markers expression at both mRNA and protein level. In addition, E2 down-regulated luminal cell type markers CK18 and CK8 and up-regulated basal cell type markers CK5 and CK14. E2 also increased intermediate type markers CK15 and CK17, while it attenuated CK19 in 3D culture. ICI182,780 blocked E2-induced EMT and cell phenotypic switching. In 3D Matrigel culture, Vimentin was co-expressed with ERα and CK17, as well as with SMemb, which is related to cell status switching and proliferation. Knockdown of ERα but not GPR30 inhibited EMT, while ERβ knockdown facilitated EMT process. Knockdown of ERα blocked E2-induced EMT both in RWPE-1 and BPH-1. MRNA expression of EMT markers was stimulated by ERα-specific agonist PPT and inhibited by ERβ-specific agonist DPN.

CONCLUSIONS

Estrogenic effect mediated by ERα can promote EMT. E2 is also an inductive factor of cell phenotypic switching. Cell type modulation is associated with E2-induced EMT in benign prostatic epithelial cells. Taken together the results support a contribution of estrogens to the pathogenesis of BPH in elderly men.

Estrogen receptors in breast and bone: from virtue of remodeling to vileness of metastasis

Bone metastasis is a prominent cause of morbidity and mortality in cancer. High rates of bone colonization in breast cancer, especially in the subtype expressing estrogen receptors (ERs), suggest tissue-specific proclivities for metastatic tumor formation. The mechanisms behind this subtype-specific organ-tropism remains largely elusive. Interestingly, as the major driver of ER+ breast cancer, ERs also have important roles in bone development and homeostasis. Thus, any agents targeting ER will also inevitably affect the microenvironment, which involves the osteoblasts and osteoclasts. Yet, how such microenvironmental effects are integrated with direct therapeutic responses of cancer cells remain poorly understood. Recent findings on ER mutations, especially their enrichment in bone metastasis, raised even more provocative questions on the role of ER in cancer-bone interaction. In this review, we evaluate the importance of ERs in bone metastasis and discuss new avenues of investigation for bone metastasis treatment based on current knowledge.

The zinc-finger transcriptional factor Slug transcriptionally downregulates ERα by recruiting lysine-specific demethylase 1 in human breast cancer

Estrogen receptor α (ERα) is related with epithelial-mesenchymal transition, invasion and metastasis, and serves as an important therapeutic predictor and prognostic factor in breast cancer patients. The triple negative breast cancer (TNBC) is characterized by loss of hormone receptors and human epidermal growth factor receptor 2 (Her2), and lacks effective targeted therapy with poor prognosis. Unfortunately, the molecular mechanisms of ERα deficiency, which becomes hormone independent and results in resistance to endocrine therapy, remain to be elucidated in breast cancer. In this study, we observed an inverse correlation between Slug, a zinc-finger transcriptional repressor, and ERα expression in both human breast cancer tissues and cell lines. In ERα-negative breast cancer patients, high Slug messenger RNA expression showed obviously shorter relapse-free survival. We found that Slug binds to the E-box located in the promoter of estrogen receptor 1 gene (ESR1) to suppress its expression. More specifically, Slug recruits lysine-specific demethylase 1 (LSD1) to the E-box and thereby inhibits ERα expression by demethylating H3K4me2, which is evidenced by the interaction between Slug and LSD1. Moreover, the amount of H3K4me2 binding to the E-box was significantly increased after LSD1 knockdown in MDA-MB-231 cells. Functionally, the ability to proliferate, invade and metastasize was significantly suppressed after knockdown of either Slug or LSD1 alone, or both simultaneously. Taken together, these results suggest that Slug transcriptionally inhibits ERα expression by recruiting LSD1 to the ESR1 promoter in breast cancers. Thus, targeted inhibition of Slug and LSD1 may restore ERα and lead to resensitization to hormone therapy, providing a novel therapeutic strategy for ERα-negative breast cancer patients, especially for TNBC.

Re-expression of miR-200c suppresses proliferation, colony formation and in vivo tumor growth of murine claudin-low mammary tumor cells

Claudin-low breast cancer is a relatively rare breast cancer subtype. These cancers are typically ER-/PR-/HER2- and express high levels of mesenchymal genes as well as genes associated with inflammation, angiogenesis and stem cell function. In addition to alterations in gene expression, it was recently demonstrated that claudin-low breast cancers express very low levels of the miR-200 family of miRNAs. Given that each miRNA can regulate tens, hundreds or even thousands of genes, miRNAs are being evaluated as therapeutic targets. In this study we show that mammary tumors from MTB-IGFIR transgenic mice and cell lines derived from these tumors represent a model of human claudin-low breast cancer and murine claudin-low mammary tumors and cell lines express only very low levels of all five members of the miR-200 family. Reduced miR-200 family expression appears to be regulated via methylation as cells and tumors expressing low levels of miR-200 family members had higher levels of CpG methylation in a putative promoter region than tumors and cells expressing high levels of miR-200 family members. Re-expression of miR-200c in murine claudin-low mammary tumor cells inhibited tumor cell proliferation and colony formation in vitro and tumor growth in vivo. With respect to tumor growth in vivo, re-expression of miR-200c was associated with a reduction in tumor vasculature and expression of Flt1 and Vegfc. Therefore, miR-200c is an important regulator of mesenchymal tumor cell growth.