The expression of oestrogen receptor (ER)-beta and its variants, but not ERalpha, in adult human mammary fibroblasts

Divergent features of ERβ isoforms in triple negative breast cancer: progress and implications for further research

Estrogen receptor β (ERβ) was discovered more than 20 years ago. However, the extent and role of ERβ expression in breast cancer remain controversial, especially in the context of triple-negative breast cancer (TNBC). ERβ exists as multiple isoforms, and a series of studies has revealed an inconsistent role of ERβ isoforms in TNBC. Our recent results demonstrated contrasting functions of ERβ1 and ERβ2/β5 in TNBC. Additional research should be conducted to explore the functions of individual ERβ isoforms and develop targeted drugs according to the relevant mechanisms. Consequently, a systematic review of ERβ isoforms is necessary. In this review, we overview the structure of ERβ isoforms and detail what is known about the function of ERβ isoforms in normal mammary tissue and breast cancer. Moreover, this review highlights the divergent features of ERβ isoforms in TNBC. This review also provides insights into the implications of targeting ERβ isoforms for clinical treatment. In conclusion, this review provides a framework delineating the roles and mechanisms of different ERβ isoforms in TNBC and sheds light on future directions for basic and clinical research.

Mapping hormone-regulated cell-cell interaction networks in the human breast at single-cell resolution

The rise and fall of estrogen and progesterone across menstrual cycles and during pregnancy regulates breast development and modifies cancer risk. How these hormones impact each cell type in the breast remains poorly understood because they act indirectly through paracrine networks. Using single-cell analysis of premenopausal breast tissue, we reveal a network of coordinated transcriptional programs representing the tissue-level response to changing hormone levels. Our computational approach, DECIPHER-seq, leverages person-to-person variability in breast composition and cell state to uncover programs that co-vary across individuals. We use differences in cell-type proportions to infer a subset of programs that arise from direct cell-cell interactions regulated by hormones. Further, we demonstrate that prior pregnancy and obesity modify hormone responsiveness through distinct mechanisms: obesity reduces the proportion of hormone-responsive cells, whereas pregnancy dampens the direct response of these cells to hormones. Together, these results provide a comprehensive map of the cycling human breast.

Phosphodiesterase Type 5 Inhibitors and Selective Estrogen Receptor Modulators Can Prevent But Not Reverse Myofibroblast Transformation in Peyronie's Disease

BACKGROUND

Myofibroblast transformation is a key step in the pathogenesis of Peyronie's disease (PD). Phosphodiesterase type 5 inhibitors (PDE5is) and selective estrogen receptor modulators (SERMs) can prevent the formation of fibrosis in in vitro and in vivo models of PD. However, it is unknown whether these drugs can also reverse established fibrosis.

AIM

To investigate whether PDE5is and SERMs can reverse transforming growth factor beta 1 (TGF-β1)-induced myofibroblast transformation and determine the point of no return.

METHODS

In-Cell enzyme-linked immunosorbent assay was used to quantify TGF-β1-induced myofibroblast transformation of human primary fibroblasts isolated from tunica albuginea (TA) of patients undergoing surgery for treatment of PD. Extracellular matrix production and collagen contraction assays were used as secondary assays. Reverse transcription-quantitative polymerase chain reaction and In-Cell enzyme-linked immunosorbent assay were used to measure drug target expression. PDE5i (vardenafil) and SERM (tamoxifen) were applied at various time points after TGF-β1.

OUTCOMES

Reversibility of myofibroblast transformation and drug target expression were investigated in a time-dependent manner in TA-derived fibroblasts.

RESULTS

Vardenafil or tamoxifen could not reverse the myofibroblast traits of alpha-smooth muscle actin expression and extracellular matrix production, whereas only tamoxifen affected collagen contraction after 72 hours of TGF-β1 treatment. Phosphodiesterase 5A and estrogen receptor (ER)-β were downregulated after 72 hours, and estrogen receptor -α protein could not be quantified. Tamoxifen could prevent myofibroblast transformation until 36 hours after TGF-β1 treatment, whereas vardenafil could prevent only 24 hours after TGF-β1 treatment. This was mirrored by downregulation of drug targets on mRNA and protein level. Furthermore, antifibrotic signaling pathways, peroxisome proliferator-activated receptor gamma and betaglycan (TGFB receptor III), were significantly downregulated after 36 hours of TGF-β1 exposure, as opposed to upregulation of profibrotic thrombospondin-1 at the same time point.

CLINICAL TRANSLATION

This study suggests that using PDE5is and SERMs might only help for early-phase PD and further highlights the need to test drugs at the appropriate stage of the disease based on their mechanism of action.

STRENGTHS & LIMITATIONS

The study uses primary human TA-derived fibroblasts that enhances translatability of the results. Limitations include that only 1 example of PDE5i- and SERM-type drug was tested. Time course experiments were only performed for marker expression experiments and not for functional assays.

CONCLUSION

This is the first study to demonstrate that timing for administration of drugs affecting myofibroblast transformation appears to be vital in in vitro models of PD, where 36 hours of TGF-β1 treatment can be suggested as a "point of no return" for myofibroblast transformation. Ilg MM, Stafford SJ, Mateus M, et al. Phosphodiesterase Type 5 Inhibitors and Selective Estrogen Receptor Modulators Can Prevent But Not Reverse Myofibroblast Transformation in Peyronie's Disease. J Sex Med 2020;17:1848-1864.

Molecular Biology in the Breast Clinics-Current status and future perspectives

Breast cancer is no longer considered a single disease, and with better understanding of cancer biology, its management has evolved over the years, into a complex individualized use of therapeutics based on variable expressions of predictive and prognostic factors. With the advent of molecular and genetic research, the complexity and diversity of breast cancer cells and their ability to survive and develop resistance to treatment strategies became more evident. At the same time, targeted therapies evolved, as specific targets were discovered such as HER2 receptor, and androgen receptor. More recent is the development of immunotherapy which aims at strengthening the host immune system to identify and kill the tumor cells. In breast cancer treatment, use of molecular tests has been a target of controversies, due to their high costs and inaccessibility in limited resource situations. Research in breast cancer is also proceeding at a rapid pace, but it is important to remember that breast cancer continues to be a complex interplay of alterations at molecular and genetic level, with the variability in expressions at protein level leading to difference in behavior and responses to treatment and overall outcome. In the succeeding paragraphs, we will try to review the available evidence in literature and attempt to understand the molecular complexity of breast cancer in order to simplify the art of treating the disease and improving outcomes.

Low-dose environmental endocrine disruptors, increase aromatase activity, estradiol biosynthesis and cell proliferation in human breast cells

BACKGROUND

Phenolic endocrine-disrupting compounds (EDCs) have long been suspected of increasing human breast cancer risk, via aromatase up-regulation; however, the metabolic effects upon aromatase in human breast cells exposed to environmentally relevant concentrations of phenolic compounds, have not been addressed.

OBJECTIVES

To examine the mechanistic responses of aromatase CYP19A1 mRNA, aromatase activity, estradiol biosynthesis and cellular proliferation, in three human breast cell lines, exposed to seven phenolic compounds, at environmentally relevant concentrations.

METHODS

MCF-7 and ZR-75-1 breast cancer cells, and HMF3A breast fibroblasts were treated with specific concentrations of p,p'-DDT, methoxychlor, benzophenone-2, bisphenol A, bisphenol S, 4-phenylphenol and n-butylparaben, with and without the presence of aromatase inhibitors and estrogen receptor inhibitors.

RESULTS

All test EDCs up-regulated aromatase mRNA, increased aromatase activity, significantly increased the aromatase-induced biosynthesis of the breast carcinogen 17β-estradiol, and increased ERα-positive breast cell proliferation.

CONCLUSION

Inadvertent exposures to 'phenolic' EDCs, increase estradiol biosynthesis, and estrogen-sensitive breast cancer proliferation.

Exploiting vulnerabilities of cancer by targeting nuclear receptors of stromal cells in tumor microenvironment

The tumor microenvironment is a complex and dynamic cellular community comprising the tumor epithelium and various tumor-supporting cells such as immune cells, fibroblasts, immunosuppressive cells, adipose cells, endothelial cells, and pericytes. The interplay between the tumor microenvironment and tumor cells represents a key contributor to immune evasiveness, physiological hardiness and the local and systemic invasiveness of malignant cells. Nuclear receptors are master regulators of physiological processes and are known to play pro-/anti-oncogenic activities in tumor cells. However, the actions of nuclear receptors in tumor-supporting cells have not been widely studied. Given the excellent druggability and extensive regulatory effects of nuclear receptors, understanding their biological functionality in the tumor microenvironment is of utmost importance. Therefore, the present review aims to summarize recent evidence about the roles of nuclear receptors in tumor-supporting cells and their implications for malignant processes such as tumor proliferation, evasion of immune surveillance, angiogenesis, chemotherapeutic resistance, and metastasis. Based on findings derived mostly from cell culture studies and a few in vivo animal cancer models, the functions of VDR, PPARs, AR, ER and GR in tumor-supporting cells are relatively well-characterized. Evidence for other receptors, such as RARβ, RORγ, and FXR, is limited yet promising. Hence, the nuclear receptor signature in the tumor microenvironment may harbor prognostic value. The clinical prospects of a tumor microenvironment-oriented cancer therapy exploiting the nuclear receptors in different tumor-supporting cells are also encouraging. The major challenge, however, lies in the ability to develop a highly specific drug delivery system to facilitate precision medicine in cancer therapy.

Robustness of biomarker determination in breast cancer by RT-qPCR: impact of tumor cell content, DCIS and non-neoplastic breast tissue

Background

Tissue heterogeneity in formalin-fixed paraffin-embedded (FFPE) breast cancer specimens may affect the accuracy of reverse transcription quantitative real-time PCR (RT-qPCR). Herein, we tested the impact of tissue heterogeneity of breast cancer specimen on the RT-qPCR-based gene expression assay MammaTyper®.

Methods

MammaTyper® quantifies the mRNA expression of the four biomarkers ERBB2, ESR1, PGR, and MKI67. Based on pre-defined cut-off values, this molecular in vitro diagnostic assay permits binary marker classification and determination of breast cancer subtypes as defined by St Gallen 2013. In this study, we compared data from whole FFPE sections with data obtained in paired RNA samples after enrichment for invasive carcinoma via macro- or laser-capture micro-dissection.

Results

Compared to whole sections, removal of surrounding adipose tissue by macrodissection generated mean absolute 40-ddCq differences of 0.28–0.32 cycles for all four markers, with ≥90% concordant binary classifications. The mean raw marker Cq values in the adipose tissue were delayed by 6 to 7 cycles compared with the tumor-enriched sections, adding a trivial linear fold change of 1.0078 to 1.0156. Comparison of specimens enriched for invasive tumor with whole sections with as few as 20% tumor cell content resulted in mean absolute differences that remained on average below 0.59 Cq. The mean absolute difference between whole sections containing up to 60% ductal carcinoma in situ (DCIS) and specimens after dissection of DCIS was only 0.16–0.25 cycles, although there was a tendency for higher gene expression in DCIS. Observed variations were related to small size of samples and proximity of values to the limit of detection.

Conclusion

Expression of ESR1, PGR, ERBB2 and MKI67 by MammaTyper® is robust in clinical FFPE samples. Assay performance was unaffected by adipose tissue and was stable in samples with as few as 20% tumor cell content and up to 60% DCIS.

Electronic supplementary material

The online version of this article (10.1186/s13000-018-0760-6) contains supplementary material, which is available to authorized users.

Mammary fibroblasts reduce apoptosis and speed estrogen-induced hyperplasia in an organotypic MCF7-derived duct model

The estrogen receptor (ER) regulates the survival and growth of breast cancer cells, but it is less clear how components of the tissue microenvironment affect ER-mediated responses. We set out to test how human mammary fibroblasts (HMFs) modulate ER signaling and downstream cellular responses. We exposed an organotypic mammary model consisting of a collagen-embedded duct structure lined with MCF7 cells to 17-β estradiol (E2), with and without HMFs in the surrounding matrix. MCF7 cells grown as ductal structures were polarized and proliferated at rates comparable to in vivo breast tissue. In both culture platforms, exposure to E2 increased ER transactivation, increased proliferation, and induced ductal hyperplasia. When the surrounding matrix contained HMFs, the onset and severity of E2-induced ductal hyperplasia was increased due to decreased apoptosis. The reduced apoptosis may be due to fibroblasts modulating ER signaling in MCF7 cells, as suggested by the increased ER transactivation and reduced ER protein in MCF7 cells grown in co-culture. These findings demonstrate the utility of organotypic platforms when studying stromal:epithelial interactions, and add to existing literature that implicate the mammary microenvironment in ER + breast cancer progression.

Pregnancy and Breast Cancer

Breast cancer is the most commonly diagnosed type of cancer among women worldwide. The majority of breast cancers are sporadic and the etiology is not well understood. Several factors have been attributed to altering the risk of breast cancer. A full-term pregnancy is a crucial factor in altering the risk. Early full-term pregnancy has been shown to reduce the lifetime risk of breast cancer, while a later first full-term pregnancy increases breast cancer risk. Epidemiological and experimental data demonstrate that spontaneous or induced abortions do not significantly alter the risk of breast cancer. In this study, we briefly discuss the different types and stages of breast cancer, various risk factors, and potential mechanisms involved in early full-term pregnancy-induced protection against breast cancer. Understanding how early full-term pregnancy induces protection against breast cancer will help design innovative preventive and therapeutic strategies. This understanding can also help in the development of molecular biomarkers that can be of tremendous help in predicting the risk of breast cancer in the general population.

Breast Tissue Composition and Immunophenotype and Its Relationship with Mammographic Density in Women at High Risk of Breast Cancer

Aim

To investigate the cellular and immunophenotypic basis of mammographic density in women at high risk of breast cancer.

Methods

Mammograms and targeted breast biopsies were accrued from 24 women at high risk of breast cancer. Mammographic density was classified into Wolfe categories and ranked by increasing density. The histological composition and immunophenotypic profile were quantified from digitized haematoxylin and eosin-stained and immunohistochemically-stained (ERα, ERβ, PgR, HER2, Ki-67, and CD31) slides and correlated to mammographic density.

Results

Increasing mammographic density was significantly correlated with increased fibrous stroma proportion (rs (22) = 0.5226, p = 0.0088) and significantly inversely associated with adipose tissue proportion (rs (22) = -0.5409, p = 0.0064). Contrary to previous reports, stromal expression of ERα was common (19/20 cases, 95%). There was significantly higher stromal PgR expression in mammographically-dense breasts (p=0.026).

Conclusions

The proportion of stroma and fat underlies mammographic density in women at high risk of breast cancer. Increased expression of PgR in the stroma of mammographically dense breasts and frequent and unexpected presence of stromal ERα expression raises the possibility that hormone receptor expression in breast stroma may have a role in mediating the effects of exogenous hormonal therapy on mammographic density.

Clinical significance of estrogen receptor β in breast and prostate cancer from biological aspects

Breast and prostate cancers are among the most common of all cancers. They are referred to as hormone-dependent cancers, because estrogen and androgen are involved in their development and growth. The effects of these hormones are mediated by their respective receptors, estrogen receptor (ER) α and androgen receptor. Around 18 years ago, a second ER, ERβ, which has a very similar structure to ERα, was discovered. Its function has been investigated using a variety of methods and biological systems, leading to our present understanding that ERβ can interact with or inhibit ERα and androgen receptor function directly and/or indirectly, suppress cell growth, and influence responsiveness to endocrine therapy. In order to apply the “inhibition of cell growth” function to cancer treatment, several specific ERβ agonists have been synthesized and are being tested for effectiveness in cancer treatment. We need to keep our eyes on ERβ.

Distinct nuclear receptor expression in stroma adjacent to breast tumors

The interaction between breast tumor epithelial and stromal cells is vital for initial and recurrent tumor growth. While breast cancer-associated stromal cells provide a favorable environment for proliferation and metastasis, the molecular mechanisms contributing to this process are not fully understood. Nuclear receptors (NRs) are intracellular transcription factors that directly regulate gene expression. Little is known about the status of NRs in cancer-associated stroma. Nuclear Receptor Low-Density Taqman Arrays were used to compare the gene expression profiles of all 48 NR family members in a collection of primary cultured cancer-associated fibroblasts (CAFs) obtained from estrogen receptor (ER)α positive breast cancers (n = 9) and normal breast adipose fibroblasts (NAFs) (n = 7). Thirty-three of 48 NRs were expressed in both the groups, while 11 NRs were not detected in either. Three NRs (dosage-sensitive sex reversal, adrenal hypoplasia critical region, on chromosome X, gene 1 (DAX-1); estrogen-related receptor beta (ERR-β); and RAR-related orphan receptor beta (ROR-β)) were only detected in NAFs, while one NR (liver receptor homolog-1 (LRH-1)) was unique to CAFs. Of the NRs co-expressed, four were significantly down-regulated in CAFs compared with NAFs (RAR-related orphan receptor-α (ROR-α); Thyroid hormone receptor-β (TR-β); vitamin D receptor (VDR); and peroxisome proliferator-activated receptor-γ (PPAR-γ)). Quantitative immunohistochemistry for LRH-1, TR-β, and PPAR-γ proteins in stromal fibroblasts from an independent panel of breast cancers (ER-positive (n = 15), ER-negative (n = 15), normal (n = 14)) positively correlated with mRNA expression profiles. The differentially expressed NRs identified in tumor stroma are key mediators in aromatase regulation and subsequent estrogen production. Our findings reveal a distinct pattern of NR expression that therefore fits with a sustained and increased local estrogen microenvironment in ER-positive tumors. NRs in CAFs may provide a new avenue for the development of intratumoral-targeted therapies in breast cancer.

Oestrogen receptors in breast cancer: basic mechanisms and clinical implications

Since the discovery of the connection between ovarian hormones and breast cancer, endocrine therapy has been an integral adjuvant treatment for patients with hormone-dependent breast cancers. Oestrogen receptor (ER) plays a central role in mediating the effects of endogenous hormones and therapeutic agents. ER serves as a prognostic marker for responsiveness to endocrine therapy and is targeted either directly by selective oestrogen receptor modulators (SERMs) and pure antagonists or indirectly by aromatase inhibitors (AIs) that block oestrogen production. A significant number of ER-positive patients, however, fail to respond to therapy or develop resistance over time. This review focuses on the current understanding of ER functions and recent advances in genomic technologies and research that have provided a global perspective on hormone and ER activity and led to a number of significant discoveries, including the roles of co-regulatory factors and non-coding RNAs. Mechanistic insights into normal ER functions and therapeutic actions of SERMs and AIs will enable the development of better predictive markers and more effective target mechanisms and ultimately facilitate improvements in disease outcomes and patient survival.

Research resource: global identification of estrogen receptor β target genes in triple negative breast cancer cells

Breast cancers that are negative for estrogen receptor α (ERα), progesterone receptor, and human epidermal growth factor receptor 2 are known as triple-negative breast cancers (TNBC). TNBCs are associated with an overall poor prognosis because they lack expression of therapeutic targets like ERα and are biologically more aggressive. A second estrogen receptor, ERβ, has been found to be expressed in 50% to 90% of ERα-negative breast cancers, and ERβ expression in TNBCs has been shown to correlate with improved disease-free survival and good prognosis. To elucidate the role of ERβ in regulating gene expression and cell proliferation in TNBC cells, the TNBC cell line MDA-MB-468 was engineered with inducible expression of full-length ERβ. In culture, ERβ expression inhibited cell growth by inducing a G1 cell cycle arrest, which was further enhanced by 17β-estradiol treatment. In xenografts, ERβ expression also inhibited tumor formation and growth, and 17β-estradiol treatment resulted in rapid tumor regression. Furthermore, genomic RNA sequencing identified both ligand-dependent and -independent ERβ target genes, some of which were also regulated by ERβ in other TNBC cell lines and correlated with ERβ expression in a cohort of TNBCs from the Cancer Genome Atlas Network. ERβ target genes were enriched in genes that regulate cell death and survival, cell movement, cell development, and growth and proliferation, as well as genes involved in the Wnt/β-catenin and the G1/S cell cycle phase checkpoint pathways. In addition to confirming the anti-proliferative effects of ERβ in TNBC cells, these data provide a comprehensive resource of ERβ target genes and suggest that ERβ may be targeted with ligands that can stimulate its growth inhibitory effects.

Estrogen receptor beta 2 is associated with poor prognosis in estrogen receptor alpha-negative breast carcinoma

PURPOSE

Our aim was to examine the prognostic significance of ERbeta1 and ERbeta2 expression in ERalpha-negative breast carcinomas.

MATERIALS AND METHODS

We evaluated nuclear and cytoplasmic expression of ERbeta1 and ERbeta2 by immunohistochemistry in a group of 95 patients with long follow-up. ERbeta1 and ERbeta2 status was correlated with clinicopathological parameters and disease outcome. Univariate and multivariate analyses of ERbeta1 and ERbeta2 as independent markers of disease-free survival (DFS) were carried out using the Cox proportional hazards model.

RESULTS

Nuclear ERbeta1 (nERbeta1) and nERbeta2 status was positively correlated (p = 0.01). nERbeta1 positivity was associated with low histological grade (p = 0.01) in all patients and in the nERbeta2-positive subgroup (p = 0.03) but not in the nERbeta2-negative (p = 0.27). nERbeta2 positivity was associated with lymph node involvement and tumor relapse in all cases (p < 0.00 and p < 0.00, respectively) and in the nERbeta1-negative subgroup (p < 0.00 and p < 0.00, respectively) but not in the nERbeta1-positive (p = 0.09 and p = 0.20, respectively). nERbeta2 positivity was associated with poor DFS in all patients (log-rank p <0.00), in the post-menopausal patient subgroup (log-rank p = 0.02) and in the HER2-negative (triple-negative) subgroup (log-rank p = 0.04). Cox multivariate analysis including ERbeta1, ERbeta2 and established clinicopathological variables highlighted ERbeta2 as an independent marker of early disease recurrence (hazard ratio 4.87; 95 % confidence interval 1.07-22.3; p = 0.04).

CONCLUSION

High nERbeta2 is an independent marker of early relapse in ERalpha-negative breast carcinoma, and in particular, in the nERbeta1-negative, the post-menopausal patient and the triple-negative subgroups. These findings suggest that inhibition of expression and/or function of ERbeta2 could improve disease outcome.

Examining the pathogenesis of breast cancer using a novel agent-based model of mammary ductal epithelium dynamics

The study of the pathogenesis of breast cancer is challenged by the long time-course of the disease process and the multi-factorial nature of generating oncogenic insults. The characterization of the longitudinal pathogenesis of malignant transformation from baseline normal breast duct epithelial dynamics may provide vital insight into the cascading systems failure that leads to breast cancer. To this end, extensive information on the baseline behavior of normal mammary epithelium and breast cancer oncogenesis was integrated into a computational model termed the Ductal Epithelium Agent-Based Model (DEABM). The DEABM is composed of computational agents that behave according to rules established from published cellular and molecular mechanisms concerning breast duct epithelial dynamics and oncogenesis. The DEABM implements DNA damage and repair, cell division, genetic inheritance and simulates the local tissue environment with hormone excretion and receptor signaling. Unrepaired DNA damage impacts the integrity of the genome within individual cells, including a set of eight representative oncogenes and tumor suppressors previously implicated in breast cancer, with subsequent consequences on successive generations of cells. The DEABM reproduced cellular population dynamics seen during the menstrual cycle and pregnancy, and demonstrated the oncogenic effect of known genetic factors associated with breast cancer, namely TP53 and Myc, in simulations spanning ∼40 years of simulated time. Simulations comparing normal to BRCA1-mutant breast tissue demonstrated rates of invasive cancer development similar to published epidemiologic data with respect to both cumulative incidence over time and estrogen-receptor status. Investigation of the modeling of ERα-positive (ER+) tumorigenesis led to a novel hypothesis implicating the transcription factor and tumor suppressor RUNX3. These data suggest that the DEABM can serve as a potentially valuable framework to augment the traditional investigatory workflow for future hypothesis generation and testing of the mechanisms of breast cancer oncogenesis.

A new insight into estrogen signaling: Yin-Yang perspective

During recent years, new advances in the field of estrogen signaling (e.g., the discovery of the second estrogen receptor named ERβ) have led to the conclusion that all the major human tissues are estrogen-responsive. The impact of estrogen on human health is far more complex and stronger than scientists had previously thought. Several scientists suggested that the interplay between ERα and ERβ (antagonism, synergism, etc.) simulates a Yin-Yang relationship. This article is intended to integrate the Yin-Yang theory of Traditional Chinese Medicine with modern scientific findings on estrogen signaling to offer a better understanding of the complex interactions between ERα and ERβ. A different approach, such as that of Yin-Yang theory, may complete the standard scientific perspective, reveal hidden meanings of the tissue-dependent ERα-ERβ predominance, and reveal new aspects of estrogen-receptor imbalance.

Hormone-responsive 3D multicellular culture model of human breast tissue

A hormone-responsive 3D human tissue-like culture system was developed in which human primary mammary epithelial cells (MECs) were co-cultured with two types of predominant mammary stromal cells on silk protein scaffolds. Silk porous scaffolds with incorporated extracellular matrix provided a compatible environment for epithelial structure morphogenesis and differentiation. The presence of stromal cells promoted MEC proliferation, induced both alveolar and ductal morphogenesis and enhanced casein expression. In contrast, only alveolar structures were observed in monocultures. The alveolar structures generated from the heterotypic cultures in vitro exhibited proper polarity similar to human breast tissue in vivo. Consistent with their phenotypic appearance, more functional differentiation of epithelial cells was also observed in the heterotypic cultures, where casein-α and -β mRNA expression were increased significantly. Additionally, this 3D multicellular culture model displayed an estrogen-responsive physiologically relevant response, evidenced by enhanced cell proliferation, aberrant morphology, changes in gene expression profile and few polarized lumen structures after estrogen treatment. This culture system offers an excellent opportunity to explore the role of cell-cell and cell-substrate interactions during mammary gland development, the consequences of hormone receptor activation on MEC behavior and morphogenesis, as well as their alteration during neoplastic transformation in human breast tissue.

Crosstalk of TGF-β and estrogen receptor signaling in breast cancer

Estrogen receptor-α (ERα) and transforming growth factor (TGF)-β signaling pathways are major regulators during mammary gland development, function and tumorigenesis. Predominantly, they have opposing roles in proliferation and apoptosis. While ERα signaling supports growth and differentiation and is antiapoptotic, mammary gland epithelia cells are very sensitive to TGF-β-induced cell cycle arrest and apoptosis. Their regulatory pathways intersect, and ERα blocks TGF-β pathway by multiple means, including direct interactions of its signaling components, Smads. However, relatively little is known of the dysfunction of their interactions in cancer. A better understanding would help to develop new strategies for breast cancer treatment.

Myoid (Muscular) Hamartoma of the Breast: Case Report and Review of the Literature

BACKGROUND: Myoid (muscular) hamartoma (MH) of the breast is a rare benign tumour-forming lesion composed of differentiated mammary glandular and stromal structures, fatty tissue, and areas of smooth muscle. It is considered to be a variant of mammary hamartoma. CASE REPORT: We report the case of a 46-year-old woman with MH, and provide a literature review explaining the origin of smooth muscle cells. Histologically, the tumour consisted of fibrolipomatous stroma containing ductal and lobular structures of the mammary gland located mainly at the tumour borders. The glandular structures showed signs of micro- and macrocystic changes, apocrine metaplasia, and adenosis. The dominant feature was the presence of a fascicular formation of spindle cells, predominantly in central parts, with incursion between glandular structures. Immunohistochemically, foci of smooth muscle tissue were positive for desmin, smooth muscle actin, and h-caldesmon. Oestrogen and progesterone receptors (PR) showed positive expression which was markedly higher for PR. There was negative expression of CD34, S-100 protein, and CD10. CONCLUSIONS: The origin of smooth muscle cells in MH is unknown. However, it is presumed to be derived from hormonally responsive breast stromal cells by smooth muscle metaplasia, based on evidence of hormone receptor expression in the lesion.

Serum oestrogen receptor alpha and beta bioactivity are independently associated with breast cancer: a proof of principle study

BACKGROUND

Oestrogens play a crucial role in breast carcinogenesis. Earlier studies have analysed the serum levels of endogenous hormones measured by conventional assays. In this study, we analysed the capacity of serum from breast cancer cases and controls to transactivate the oestrogen receptor alpha (ER-alpha) and beta (ER-beta).

METHODS

We used a receptor oestrogen-responsive element (ERE) -- the green fluorescent protein (GFP)-reporter test system in Saccharomyces cerevisiae. Oestrogen receptor-alpha or ER-beta bioactivity was determined in serum from 182 randomly chosen postmenopausal women with breast cancer and from 188 age-matched controls.

RESULTS

High serum ER-alpha and ER-beta bioactivity were independently associated with the presence of breast cancer. Women whose levels of serum ER-alpha and ER-beta bioactivity were in the highest quintile among controls had a 7.57-(95% confidence interval (CI): 2.46-23.32; P=0.0004) and a 10.14 (95% CI: 3.19-32.23; P<0.0001)-fold risk for general and oestrogen receptor-positive breast cancer, respectively.

CONCLUSION

The use of serum ER-alpha and ER-beta bioactivity assays as clinical tools in the management of breast cancer warrants further research. Future studies will dictate whether surrogate markers of ER-alpha and ER-beta bioactivity will provide a means to monitor the efficacy of anti-endocrine, adjuvant and chemopreventive strategies.

Identification of molecular distinctions between normal breast-associated fibroblasts and breast cancer-associated fibroblasts

Stromal fibroblasts influence the behavior of breast epithelial cells. Fibroblasts derived from normal breast (NAF) inhibit epithelial growth, whereas fibroblasts from breast carcinomas (CAF) have less growth inhibitory capacity and can promote epithelial growth. We sought to identify molecules that are differentially expressed in NAF versus CAF and potentially responsible for their different growth regulatory abilities. To determine the contribution of soluble molecules to fibroblast–epithelial interactions, NAF were grown in 3D, transwell or direct contact co-cultures with MCF10AT epithelial cells. NAF suppressed proliferation of MCF10AT in both direct contact and transwell co-cultures, but this suppression was significantly greater in direct co-cultures, indicating involvement of both soluble and contact factors. Gene expression profiling of early passage fibroblast cultures identified 420 genes that were differentially expressed in NAF versus CAF. Of the eight genes selected for validation by real-time PCR, FIBULIN 1, was overexpressed in NAF, and DICKKOPF 1, NEUREGULIN 1, PLASMINOGEN ACTIVATOR INHIBITOR 2, and TISSUE PLASMINOGEN ACTIVATOR were overexpressed in CAF. A higher expression of FIBULIN 1 in normal- than cancer-associated fibroblastic stroma was confirmed by immunohistochemistry of breast tissues. Among breast cancers, stromal expression of Fibulin 1 protein was higher in estrogen receptor α-positive cancers and low stromal expression of Fibulin 1 correlated with a higher proliferation of cancer epithelial cells. In conclusion, expression profiling of NAF and CAF cultures identified many genes with potential relevance to fibroblast–epithelial interactions in breast cancer. Furthermore, these early passage fibroblast cultures can be representative of gene expression in stromal fibroblasts in vivo.

Oestrogen receptor-beta1 but not oestrogen receptor-betacx is of prognostic value in apocrine carcinoma of the breast

Apocrine carcinoma of the breast, which frequently expresses oestrogen receptor-beta (ER-beta) in the absence of ER-alpha and only infrequently is treated endocrinologically, gives an opportunity to investigate the clinicopathological role of ER-beta in breast cancer independent of ER-alpha expression or tamoxifen treatment. Several isotypes of ER-beta, ER-beta1-5 etc., have been identified thus far; however, the clinicopathological importance of each ER-beta isotype in breast cancer is still uncertain. Here we aimed to clarify the clinicopathological importance of ER-beta1 and ER-betacx (ER-beta2) in apocrine carcinomas, immunohistochemically examining expressions of ER-beta1 and ER-betacx in 47 apocrine carcinomas. Positivity for ER-beta1 and ER-betacx was observed in 41 (87%) and 18 (38%) of 47 cases, respectively. ER-beta1 positivity was related to smaller tumor size (P=0.0359), lower histological grade (P=0.0322), and higher disease-free survival (P<0.0001), whereas ER-betacx status was related to none of these parameters. ER-beta1 positivity was also associated with favorable clinical outcome in 24 so-called triple-negative (ER-alpha-negative/PR-negative/HER2-negative) apocrine carcinomas. ER-beta1 itself, independent of ER-alpha expression and tamoxifen treatment, seems to have a tumor-suppressive effect, at least in apocrine carcinomas. Further study of ER-beta1 is desired to optimize breast cancer treatment.

Membrane ERalpha-dependent activation of PKCalpha in endometrial cancer cells by estradiol

The purpose of this study was to investigate the role of the oestrogen receptor subtypes ERalpha and ERbeta in mediating the non-genomic effects of 17-beta-estradiol (E(2)) in two human endometrial cancer cell lines (RL95-2 and HEC-1A) expressing different levels of these receptor subtypes. Western blotting analysis using phosphorylation site-specific antibodies showed that physiological concentrations of E(2) rapidly (<20 min) activated PKCalpha, but not PKCdelta in the RL95-2 cell line. E(2) had no effect on PKCalpha or PKCdelta activity in the HEC-1A cell line and suppressed basal levels of PKA activity in both cell lines. PKCalpha activation coincided with its membrane translocation. ERalpha was detected in the RL95-2 cell line by Western blotting and RT-PCR but not in the HEC-1A cells, which did express ERbeta. A selective ERalpha agonist PPT had the same effect as E(2) on PKCalpha activation in the RL95-2 cells, but the selective ERbeta agonist DPN had no such effect. A 46kDa variant of ERalpha increased in abundance in the cell membrane within 20 min of E(2) treatment suggesting that ERalpha mediated the E(2) non-genomic effects on PKCalpha through the formation of a membrane associated signalling complex.

Histologic changes in the breast with menopausal hormone therapy use: correlation with breast density, estrogen receptor, progesterone receptor, and proliferation indices

OBJECTIVE

This retrospective study systematically compared mammographic density with histology in women receiving or not receiving menopausal hormone therapy (HT).

DESIGN

This study was approved by the institutional review board. Twenty-eight postmenopausal women using HT were matched with 28 postmenopausal women not using HT at the time of breast cancer diagnosis. Noncancerous tissue from mastectomy specimens was examined histologically to quantitate the content of fibrous stroma, ducts, and lobule types 1, 2, and 3. Tissue samples were also evaluated for estrogen receptor, progesterone receptor, and Ki67 activity in the ducts and lobules. Breast density was quantified by digitizing the contralateral mammogram and computer-assisted interactive thresholding.

RESULTS

High breast density in women using HT was correlated with greater fibrous stroma (P = 0.020) and lobule type 1 (P = 0.016). Breast density also correlated with Ki67 activity in the ducts (P = 0.031) and lobules (P= 0.023) for both groups combined. Estrogen and progesterone receptors did not correlate with either breast density or HT use.

CONCLUSIONS

Increased fibrous stroma and lobule type 1 are associated with increasing mammographic density in women using HT, independent of estrogen and progesterone receptor up-regulation. These findings suggest that increased breast density may be mediated through a paracrine effect. The increase in breast cancer risk with HT use may be due to an increase in target lobule type 1 cells.

Estrogen receptor beta (ESR2) polymorphisms in familial and sporadic breast cancer

Estrogen is involved in both normal mammary development and in breast carcinogenesis. A family history of disease and exposure to estrogen are major risk factors for developing breast cancer. Estrogen exerts its biological effects through binding to the estrogen receptors, estrogen receptor alpha (ESR1) and the more recently discovered estrogen receptor beta (ESR2). Genetic variation in genes involved in estrogen biosynthesis, metabolism and signal transduction have been suggested to play a role in breast cancer risk. We therefore tested the hypothesis that common genetic variants of the ESR2 gene may be associated with increased risk for breast cancer and this risk may vary between breast cancer groups. We investigated three common ESR2 polymorphisms, rs1256049 (G1082A), rs4986938 (G1730A) and rs928554 (Cx+56 A-->G) for association to breast cancer risk. A total of 723 breast cancer cases and 480 controls were included in the study. Of the breast cancer cases, 323 were sporadic and 400 were familial, the familial cases were further divided into familial high-risk and familial low-risk breast cancer cases. We found no overall statistically significant association for any of the single polymorphisms studied. Haplotype analysis suggested one haplotype associated with increased risk in sporadic breast cancer patients (OR = 3.0, p = 0.03). Further analysis is needed to elucidate the role of estrogen receptor beta in breast cancer susceptibility.

Oestrogen-receptor-mediated transcription and the influence of co-factors and chromatin state

Oestrogen receptor-alpha (ERalpha)-regulated transcription in breast cancer cells involves protein co-factors that contribute to the regulation of chromatin structure. These include co-factors with the potential to regulate histone modifications such as acetylation or methylation, and therefore the transcriptional state of target genes. Although much of the information regarding the interaction of specific co-factors with ER has been generated by studying specific promoter regions, we now have an improved understanding of the nature of these interactions and are better placed to relate these with ER activity and potentially with the activity of breast cancer drugs, including tamoxifen.

Estrogen receptor ?1 and the ?2/?cx isoforms in nonneoplastic endometrium and in endometrioid carcinoma

Estrogen receptor beta (ERbeta) has five carboxyl-terminal (C-terminal) isoforms derived from alternative splicing. ERbeta1 is the wild-type receptor whereas ERbeta2/betacx lacks the activation function (AF)-2 core essential for ligand-dependent transcriptional activation and so behaves as a dominant-negative receptor affecting the function of ERalpha. The objective of this study was to analyze the expression of ERbeta1 and ERbeta2/betacx isoforms in nonneoplastic endometrium and endometrioid carcinoma. The study was conducted on samples of 22 proliferative endometrium, 15 secretory endometrium, 20 simple hyperplasia (without atypia), and 26 endometrioid carcinomas. The transcript and protein levels were determined by semiquantitative reverse transcriptase-polymerase chain reaction and immunohistochemistry, respectively. For the detection of ERbeta2/betacx protein, a polyclonal antibody was raised to its unique C-terminus, characterized, and used in immunohistochemistry. The two ERbeta isoforms are expressed in the proliferative and secretory phase endometrium with no significant change in their relative levels. The levels of the ERbeta1 isoform were lower as compared to the levels of ERbeta2 in all the groups studied. Expression of ERbeta2/betacx was decreased in endometrioid carcinoma as compared to proliferative endometrium (P < 0.01). A significant decrease of the ERbeta2/ERbetacx transcript was observed with higher grade tumors (P = 0.041). Progesterone receptor (PR) expression was not influenced by either of the ERbeta isoforms which was observed by logistic regression analysis in all the groups. The coexpression of ERbeta2/betacx with ERalpha did not affect PR levels (logistic regression analysis). Thus, we conclude in the human endometrium, there is significant ERbeta2/betacx isoform expression and alterations in its levels could be involved in endometrial cancer progression.

Contributions of estrogen to ER-negative breast tumor growth

Breast cancer is a hormone-based disease with numerous factors contributing to the lifetime risk of developing the disease. While breast cancer risk is reduced by nearly 50% after one full term pregnancy, women over the age of 25 have a significantly greater risk of developing breast cancer immediately following parturition compared to their nulliparous counterparts. It is widely presumed that the increased risk of developing breast cancer following pregnancy is due to the ability of pregnancy-associated hormones to promote the further proliferation of an initiated target cell population. It is surprising however, that the majority of breast cancers that develop following pregnancy lack appreciable expression of either the estrogen or progesterone receptors. This important observation suggests that if hormones play a part in promoting breast cancer following pregnancy, they may not be doing so through direct binding to hormone receptor molecules expressed by breast cancer cells. To reconcile this conceptual conflict we investigated the hypothesis that steroid hormones promote the outgrowth of ER-negative cancers by influencing host cell types distinct from the breast epithelium itself. We demonstrated that increasing the levels of circulating estrogens is sufficient to promote the formation and progression of ER-negative cancers while, pharmacologically inhibiting estrogen synthesis following pregnancy prevents ER-negative tumor formation. Moreover, we demonstrate that the effects of estrogen act via a systemic increase in host angiogenesis, in part through increased mobilization and recruitment of bone marrow stromal derived cells into sites of angiogenesis and to a growing tumor mass. Taken together, these data suggest that estrogen may promote the growth of ER-negative cancers by acting on cells distinct from the cancer cells to stimulate angiogenesis.

Estrogen receptor-beta is expressed in stromal cells of fibroadenoma and phyllodes tumors of the breast

An estrogen dependency has been suggested for the growth of fibroadenomas: however, thus far, none of the steroid hormone receptors acting on breast tissues has been demonstrated in the stroma of breast fibroepithelial lesions. In this study, the expression of estrogen receptor (ER)-alpha and -beta was investigated by immunohistochemistry in 33 fibroadenomas and in 30 benign, three borderline and seven malignant phyllodes tumors, all with spindle cell growth and in one distant metastasis. In addition, the presence of ER-beta mRNA and its variants was evaluated by RT-PCR in microdissected stroma. The possible correlation between hormone receptor expression and differentiation processes of stromal cells was investigated by smooth muscle actin and calponin immunostaining. ER-beta was the only hormone receptor expressed by stroma of fibroadenomas and phyllodes tumors, both at protein and mRNA level. The highest percentage of ER-beta was observed in fibroadenomas with cellular stroma and in phyllodes tumors. In both lesions, ER-beta-positive stromal cells showed expression of smooth muscle actin and/or calponin, as demonstrated by double immunostaining. In addition, the mean age at diagnosis was significantly lower in patients with ER-beta-positive vs ER-beta-negative fibroadenomas. In contrast, in phyllodes tumors, ER-beta expression was higher in older patients. In conclusion, (i) only ER-beta is detected in the stroma of fibroadenomas and phyllodes tumors; (ii) its expression correlates with the expression of smooth muscle markers and suggests a role of ER-beta in myofibroblastic differentiation of stromal cells. These two results, together with the young age of patients carrying fibroadenomas with highly ER-beta-positive stroma cells, may further indicate a hormone-receptor mechanism involved in regulating the growth of fibroadenomas. Conversely, the older age of patients with ER-beta-rich phyllodes tumors suggests that mechanisms, probably independent from estrogen stimulation, act on the growth of these tumors.

Isoflavones made simple - genistein's agonist activity for the beta-type estrogen receptor mediates their health benefits

Soy isoflavones, the focus of much research and controversy, are often referred to as "weak estrogens". In fact, genistein is a relatively potent agonist for the recently characterized beta isoform of the estrogen receptor (ERbeta). The low nanomolar serum concentrations of unconjugated free genistein achieved with high-nutritional intakes of soy isoflavones are near the binding affinity of genistein for this receptor, but are about an order of magnitude lower than genistein's affinity for the "classical" alpha isoform of the estrogen receptor (ERalpha). Moreover, these concentrations are far too low to inhibit tyrosine kinases or topoisomerase II, in vitro activities of genistein often cited as potential mediators of its physiological effects. The thesis that these physiological effects are in fact mediated by ERbeta activation provides a satisfying rationale for genistein's clinical activities. Hepatocytes do not express ERbeta; this explains why soy isoflavones, unlike oral estrogen, neither modify serum lipids nor provoke the prothrombotic effects associated with increased risk for thromboembolic disorders. The lack of uterotrophic activity of soy isoflavones reflects the fact that ERalpha is the exclusive mediator of estrogen's impact in this regard. Vascular endothelium expresses both ERalpha and ERbeta, each of which has the potential to induce and activate nitric oxide synthase; this may account for the favorable influence of soy isoflavones on endothelial function in postmenopausal women and ovariectomized rats. The ERbeta expressed in osteoblasts may mediate the reported beneficial impact of soy isoflavones on bone metabolism. Suggestive evidence that soy-rich diets decrease prostate cancer risk, accords well with the observation that ERbeta appears to play an antiproliferative role in healthy prostate. In the breast, ERalpha promotes epithelial proliferation, whereas ERbeta has a restraining influence in this regard - consistent with the emerging view that soy isoflavones do not increase breast cancer risk, and possibly may diminish it. Premenopausal women enjoy a relative protection from kidney failure; since ERbeta is an antagonist of TGF-beta signaling in mesangial cells, soy isoflavones may have nephroprotective potential. Estrogen also appears to protect women from left ventricular hypertrophy, and recent evidence suggests that this effect is mediated by ERbeta. In conjunction with reports that isoflavones may have a modestly beneficial impact on menopausal symptoms - perhaps reflecting the presence of ERbeta in the hypothalamus - these considerations suggest that soy isoflavone regimens of sufficient potency may represent a safe and moderately effective alternative to HRT in postmenopausal women. Further clinical research is required to characterize the impact of optimal genistein intakes on endothelial and bone function in men. Studies with ERbeta-knockout mice could be helpful for clarifying whether ERbeta does indeed mediate the chief physiological effects of low nanomolar genistein. S-equol, a bacterial metabolite of daidzein, has an affinity for ERbeta nearly as high as that of genistein; whether this compound contributes meaningfully to the physiological efficacy of soy isoflavones in some individuals is still unclear.

ERbeta protein expression in female cynomolgus monkey and CF-1 mouse brain: Western analysis

In humans and rodents, multiple ERbeta variants with sizes ranging from 477-549 amino acids (aa) have been described. The identification of these variants in target tissues has important implications for estrogen signaling and cellular responsiveness. Western blot analysis using two anti-ERbeta antibodies specific for mammalian ERbeta sequences (PA1-310B and PA1-311) was employed to examine ERbeta protein expression in neural tissues from ovariectomized (OVX) cynomolgus macaques and CF-1 mice as well as to assess potential regulatory effects of acute and extended estradiol (E(2)) treatment. In hypothalamic extracts from both species, a single ERbeta immunoreactive (ERbeta-ir) band was detected at approximately 54 kDa, corresponding to the expected molecular weight for ERbeta477 and/or 485. In cynomolgus females, oral E(2) administration for 16 weeks had no apparent effect on hypothalamic ERbeta protein expression. In mouse, a single injection of E(2) did not change hypothalamic ERbeta protein levels 1.5, 4, 8, 16, or 24 h after injection. Extending the hormonal treatment to 4 or 21 days in OVX female mice also had no effect on the level of hypothalamic ERbeta protein. Additional regional analyses in female mouse brain with PA1-310B antibody showed that a second, 59 kDa ERbeta-ir band was present in cortex, striatum, hippocampus, and amygdala that could represent one or both of the larger ERbeta variants (530 and 549aa). The expression level of the second ERbeta isoform exhibited regional variation, with the strongest immunoreactivity detected in cortex and amygdala. Elucidating the functions of these ERbeta isoforms in the CNS will facilitate our understanding of the tissue- and promoter-specific actions of estrogen.

Reflections on the discovery and significance of estrogen receptor beta

We have known for many years that estrogen is more than the female hormone. It is essential in the male gonads, and in both sexes, estrogen has functions in the skeleton and central nervous system, on behavior, and in the cardiovascular and immune systems. An important aspect of the discovery of estrogen receptor (ER) beta is that the diverse functions of estrogen can now be divided into those mediated by ERalpha and those mediated by ERbeta. Pharmacological exploitation of this division of the labors of estrogen is facilitated by the ligand-binding specificity and selective tissue distribution of the two ERs. Because the ligand binding domains of ERalpha and ERbeta are significantly different from each other, selective ligands can be (and have been) developed to target the estrogenic pathway that is malfunctioning, without interfering with the other estrogen-regulated pathways. Because of the absence of ERbeta from the adult pituitary and endometrium, ERbeta agonists can be used to target ERbeta with no risk of adverse effects from chemical castration and uterine cancer. Some of the diseases in which there is hope that ERbeta agonists will be of benefit are prostate cancer, autoimmune diseases, colon cancer, malignancies of the immune system, and neurodegeneration.