Clinical importance of estrogen receptor-beta evaluation in breast cancer patients treated with adjuvant tamoxifen therapy

Protein arginine N-methyltransferase 2 reverses tamoxifen resistance in breast cancer cells through suppression of ER-α36

Breast cancer is one of the most common malignancies in females, and 17β-estradiol (E2)/estrogen receptor α (ERα) signaling plays an important role in the initiation and progression of breast cancer. The role of the ER-α subtype and its co-regulator in the initiation of breast cancer and the occurrence of tamoxifen resistance remains to be further elucidated. In our previous studies, protein arginine N-methyltransferase 2 (PRMT2), a co-regulator of estrogen receptor-α (ER-α), was confirmed to interact with ER-α66 and has the ability to inhibit cell proliferation in breast cancer cells. In the present study, we found that tamoxifen treatment induced a decrease in PRMT2 and an increase in ER-α36 as well as ER-α36-mediated non-genomic effect in MDA-MB-231 cells, which were relatively resistant to tamoxifen by contrast to MCF-7 cells. Moreover, PRMT2 was able to interact with ER-α36 directly, suppress ER-α36 and downstream PI3K/Akt and MAPK/ERK signaling, reversing the tamoxifen resistance of breast cancer cells. The present study may be meaningful for understanding the role of PRMT2 in breast cancer progression and for developing a new endocrine therapeutic strategy for breast cancer patients with tamoxifen resistance.

Clinical significance of androgen receptor expression in triple negative breast cancer-an immunohistochemistry study

Androgen receptor (AR) is closely associated with the occurrence and progression of breast cancer; however, the clinical significance of it in triple negative breast cancer (TNBC) has been controversial. There is a limited amount of research regarding the effect of neoadjuvant chemotherapy on AR expression. By examining the expression of AR in patients with TNBC, the aim of the present study is to explore the clinical significance of AR and provide evidence for AR-directed treatment in TNBC. A total of 188 patients with primary TNBC with complete medical records were included in this retrospective study. Tumor sections from 41 patients (21.8%) were positive for AR, which was more often detected in small tumors (P=0.042) and cases with no lymph node involvement (P=0.032). Among them, 102 were treated with neoadjuvant chemotherapy (NAC). A total of 17 patients (16.7%) exhibited pathological complete response. However, the patient response was irrelevant to AR expression. Matched pathological tissues before and after NAC were collected for 49 cases, suggesting an enrichment of AR-expressing tumors following chemotherapy (P=0.008). Further analysis indicated that AR expression had no correlation with the disease-free and overall survival of patients with general TNBC; rather, it predicted a poor survival of the patients with stage III TNBC in comparison with those at earlier stages (P=0.035). AR expression occurs more often in small TNBC tumors or in cases with no lymph node metastasis. It is associated with a poor prognosis of the patients with advanced stages of tumors.

Extranuclear signaling by sex steroid receptors and clinical implications in breast cancer

Estrogen and progesterone play essential roles in the development and progression of breast cancer. Over 70% of breast cancers express estrogen receptors (ER) and progesterone receptors (PR), emphasizing the need for better understanding of ER and PR signaling. ER and PR are traditionally viewed as transcription factors that directly bind DNA to regulate gene networks. In addition to nuclear signaling, ER and PR mediate hormone-induced, rapid extranuclear signaling at the cell membrane or in the cytoplasm which triggers downstream signaling to regulate rapid or extended cellular responses. Specialized membrane and cytoplasmic proteins may also initiate hormone-induced extranuclear signaling. Rapid extranuclear signaling converges with its nuclear counterpart to amplify ER/PR transcription and specify gene regulatory networks. This review summarizes current understanding and updates on ER and PR extranuclear signaling. Further investigation of ER/PR extranuclear signaling may lead to development of novel targeted therapeutics for breast cancer management.

ERβ alters the chemosensitivity of luminal breast cancer cells by regulating p53 function

Estrogen receptor α (ERα)-positive breast cancers tend to develop resistance to both endocrine therapy and chemotherapy. Despite recent progress in defining molecular pathways that confer endocrine resistance, the mechanisms that regulate chemotherapy response in luminal tumors remain largely elusive. Luminal tumors often express wild-type p53 that is a major determinant of the cellular DNA damage response. Similar to p53, the second ER subtype, ERβ, has been reported to inhibit breast tumorigenesis by acting alone or in collaboration with p53. However, a synergistic mechanism of action has not been described. Here, we suggest that ERβ relies on p53 to elicit its tumor repressive actions in ERα-positive breast cancer cells. Upregulation of ERβ and treatment with ERβ agonists potentiates the tumor suppressor function of p53 resulting in decreased survival. This effect requires molecular interaction between the two proteins that disrupts the inhibitory action of ERα on p53 leading to increased transcriptional activity of p53. In addition, we show that the same interaction alters the chemosensitivity of endocrine-resistant cells including their response to tamoxifen therapy. Our results suggest a collaboration of ERβ and p53 tumor suppressor activity in breast cancer cells that indicates the importance of ligand-regulated ERβ as a tool to target p53 activity and improve the clinical management of resistant disease.

Pharmacological activation of estrogen receptor beta augments innate immunity to suppress cancer metastasis

Metastases constitute the greatest causes of deaths from cancer. However, no effective therapeutic options currently exist for cancer patients with metastasis. Estrogen receptor β (ERβ), as a member of the nuclear receptor superfamily, shows potent tumor-suppressive activities in many cancers. To investigate whether modulation of ERβ could serve as a therapeutic strategy for cancer metastasis, we examined whether the selective ERβ agonist LY500307 could suppress lung metastasis of triple-negative breast cancer (TNBC) and melanoma. Mechanistically, while we observed that LY500307 potently induced cell death of cancer cells metastasized to lung in vivo, it does not mediate apoptosis of cancer cells in vitro, indicating that the cell death-inducing effects of LY500307 might be mediated by the tumor microenvironment. Pathological examination combined with flow cytometry assays indicated that LY500307 treatment induced significant infiltration of neutrophils in the metastatic niche. Functional experiments demonstrated that LY500307-treated cancer cells show chemotactic effects for neutrophils and that in vivo neutrophil depletion by Ly6G antibody administration could reverse the effects of LY500307-mediated metastasis suppression. RNA sequencing analysis showed that LY500307 could induce up-regulation of IL-1β in TNBC and melanoma cells, which further triggered antitumor neutrophil chemotaxis. However, the therapeutic effects of LY500307 treatment for suppression of lung metastasis was attenuated in IL1B^-/- murine models, due to failure to induce antitumor neutrophil infiltration in the metastatic niche. Collectively, our study demonstrated that pharmacological activation of ERβ could augment innate immunity to suppress cancer metastatic colonization to lung, thus providing alternative therapeutic options for cancer patients with metastasis.

Fulvestrant inhibits growth of triple negative breast cancer and synergizes with tamoxifen in ERα positive breast cancer by up-regulation of ERβ

The estrogen receptor-alpha (ERα) is used as a predictive marker for anti-estrogen therapy in breast cancer patients. In addition to aromatase inhibitors, ERα can be targeted at the receptor level using the receptor modulator tamoxifen or by the pure anti-estrogen fulvestrant. The role of the second ER, ER-beta (ERβ), as a therapeutic target or prognostic marker in breast cancer is still elusive. Hitherto, it is not known if ERα+/ERβ+ breast cancers would benefit from a treatment strategy combining tamoxifen and fulvestrant or if fulvestrant exert any therapeutic effects in ERα-/ERβ+ breast cancer. Here, we report that fulvestrant up-regulated ERβ in ERα+/ERβ+ breast cancer and in triple negative ERβ+ breast cancers (ERα-/ERβ+). In ERα+/ERβ+ breast cancer, a combination therapy of tamoxifen and fulvestrant significantly reduced tumor growth compared to either treatment alone both in vivo and in vitro. In ERα-/ERβ+ breast cancer fulvestrant had potent effects on cancer growth, in vivo as well as in vitro, and this effect was dependent on intrinsically expressed levels of ERβ. The role of ERβ was further confirmed in cells where ERβ was knocked-in or knocked-down. Inhibition of DNA methyltransferase (DNMT) increased the levels of ERβ and fulvestrant exerted similar potency on DNMT activity as the DNMT inhibitor decitabine. We conclude that fulvestrant may have therapeutic potential in additional groups of breast cancer patients; i) in ERα+/ERβ+ breast cancer where fulvestrant synergizes with tamoxifen and ii) in triple negative/ERβ+ breast cancer patients, a subgroup of breast cancer patients with poor prognosis.

Reduced expression of oestrogen receptor-β is associated with tumour invasion and metastasis in oestrogen receptor-α-negative human papillary thyroid carcinoma

Oestrogens play an important role in the development and progression of papillary thyroid carcinoma (PTC) through oestrogen receptor (ER)-α and -β, which may exert different or even opposing actions in PTC. The roles of ERβ in ERα-negative PTC are still not clear. This study investigated the expression dynamics of ERβ1 (wild-type ERβ) and its clinical significance in female ERα-negative PTC patients. ERβ1 expression was detected in thyroid tissues of 136 female patients diagnosed with PTC. The relationships between ERβ1 expression and clinicopathological/biological factors were also analysed in female ERα-negative PTC patients. The total score for ERβ1 was significantly lower in female ERα-negative PTC patients with LNM or ETE when compared to those without LNM or ETE (Z = -2.923, P = 0.003 and Z = -3.441, P = 0.001). Accordingly, the total score for ERβ1 was significantly higher in ERα-negative PTC patients expressing E-cadherin compared to patients negative for E-cadherin expression (Z = -2.636, P = 0.008). The total score was lower in ERα-negative PTC patients positive for VEGF expression compared to those negative for VEGF expression (Z = -1.914, P = 0.056). This preliminary study indicates that reduced expression of ERβ1 in female ERα-negative PTC patients is associated with greater progression of the disease. This may provide insights into the underlying molecular mechanisms of ERβ1 and could help design targeted approaches for treating or even preventing this disease.

Estrogen Signaling in ERα-Negative Breast Cancer: ERβ and GPER

Estrogen receptors are important regulators of the growth of breast tumors. Three different receptors for estrogens have been identified in breast tumors, two nuclear receptors, ERα and ERβ, and a G-protein coupled estrogen receptor 1 (GPER) that initiates non-genomic effects of estrogens in the cytosol. Recent findings show that the stimulation of cytoplasmic ERα and ERβ also triggers non-genomic signaling pathways. The treatment of breast cancer with anti-estrogens depends on the presence of ERα. About 40% of all breast cancers, however, do not express ERα. One subgroup of these tumors overexpress Her-2, another important group is designated as triple-negative breast cancer, as they neither express ERα, nor progesterone receptors, nor do they overexpress Her-2. This review addresses the signaling of ERβ and GPER in ERα-negative breast tumors. In addition to the well-established EGF-receptor transactivation pathways of GPER, more recent findings of GPER-dependent activation of FOXO3a, the Hippo-pathway, and HOTAIR-activation are summarized.

ERβ decreases the invasiveness of triple-negative breast cancer cells by regulating mutant p53 oncogenic function

Most (80%) of the triple-negative breast cancers (TNBCs) express mutant p53 proteins that acquire oncogenic activities including promoting metastasis. We previously showed that wild-type ERβ (ERβ1) impedes epithelial to mesenchymal transition (EMT) and decreases the invasiveness of TNBC cells. In the present study we searched for signaling pathways that ERβ1 uses to inhibit EMT and invasion in TNBC cells. We show that ERβ1 binds to and opposes the transcriptional activity of mutant p53 at the promoters of genes that regulate metastasis. p63 that transcriptionally cooperates with mutant p53 also binds to ERβ1. Downregulation of p63 represses the epithelial phenotype of ERβ1-expressing cells and alters the expression of mutant p53 target genes. These results describe a novel mechanism through which ERβ1 can disturb oncogenic signals to inhibit aggressiveness in TNBCs.

Inhibitory modulation of human estrogen receptor α and β activities by dicyclohexyl phthalate in human breast cancer cell lines

Phthalate esters (PAEs) are man-made compounds that are used widely in industry, and the ubiquitous exposure of humans to PAEs has been reported. Although some PAEs have been suggested to function as xenoestrogens in in vitro systems, such as human estrogen receptors (ERs) expressed in Chinese hamster ovary (CHO)-K1 cells, few studies have attempted to elucidate whether PAEs affect human ERα/ERβ-mediated signaling in human breast cancer cells (i.e., combination between human ERs and human cells). Thus, further experiments are needed in order to clarify the activities of PAEs. Among the 9 PAEs (carbon# in the side chains: 2-8) investigated, dibutyl phthalate (DBP), dipentyl phthalate (DPENP), and dicyclohexyl phthalate (DCHP) were found to exhibit strong anti-estrogenic activities in MCF-7 cells (ER-positive) in the presence of 1 nM 17β-estradiol (E2). Since limited information is currently available on DPENP and DCHP, we herein focused on these two PAEs. Experiments using MDA-MB-231 cells (ER-negative) transfected with human ERα or ERβ expression plasmids revealed that DCHP was a markedly stronger anti-estrogenic PAE than DPENP; DCHP inhibited ERα and ERβ activities stimulated by 1 nM E2 with IC₅₀ values of ~5 and 11.2 µM, respectively. Furthermore, DCHP abrogated diarylpropionitrile (DPN)-stimulated ERβ activity with an IC₅₀ value of 5.17 µM, which was approximately 2-fold stronger than that of DPENP (IC₅₀ = 10 µM). The results of the present study suggest that PAEs (DCHP) function not only as an anti-estrogen for ERα, but also for ERβ, at least in human breast cancer cell lines.

Estrogen Receptor β as a Therapeutic Target in Breast Cancer Stem Cells

Background

Breast cancer cells with tumor-initiating capabilities (BSCs) are considered to maintain tumor growth and govern metastasis. Hence, targeting BSCs will be crucial to achieve successful treatment of breast cancer.

Methods

We characterized mammospheres derived from more than 40 cancer patients and two breast cancer cell lines for the expression of estrogen receptors (ERs) and stem cell markers. Mammosphere formation and proliferation assays were performed on cells from 19 cancer patients and five healthy individuals after incubation with ER-subtype selective ligands. Transcriptional analysis was performed to identify pathways activated in ERβ-stimulated mammospheres and verified using in vitro experiments. Xenograft models (n = 4 or 5 per group) were used to study the role of ERs during tumorigenesis.

Results

We identified an absence of ERα but upregulation of ERβ in BSCs associated with phenotypic stem cell markers and responsible for the proliferative role of estrogens. Knockdown of ERβ caused a reduction of mammosphere formation in cell lines and in patient-derived cancer cells (40.7%, 26.8%, and 39.1%, respectively). Gene set enrichment analysis identified glycolysis-related pathways (false discovery rate < 0.001) upregulated in ERβ-activated mammospheres. We observed that tamoxifen or fulvestrant alone was insufficient to block proliferation of patient-derived BSCs while this could be accomplished by a selective inhibitor of ERβ (PHTPP; 53.7% in luminal and 45.5% in triple-negative breast cancers). Furthermore, PHTPP reduced tumor initiation in two patient-derived xenografts (75.9% and 59.1% reduction in tumor volume, respectively) and potentiated tamoxifen-mediated inhibition of tumor growth in MCF7 xenografts.

Conclusion

We identify ERβ as a mediator of estrogen action in BSCs and a novel target for endocrine therapy.

Insufficient antibody validation challenges oestrogen receptor beta research

The discovery of oestrogen receptor β (ERβ/ESR2) was a landmark discovery. Its reported expression and homology with breast cancer pharmacological target ERα (ESR1) raised hopes for improved endocrine therapies. After 20 years of intense research, this has not materialized. We here perform a rigorous validation of 13 anti-ERβ antibodies, using well-characterized controls and a panel of validation methods. We conclude that only one antibody, the rarely used monoclonal PPZ0506, specifically targets ERβ in immunohistochemistry. Applying this antibody for protein expression profiling in 44 normal and 21 malignant human tissues, we detect ERβ protein in testis, ovary, lymphoid cells, granulosa cell tumours, and a subset of malignant melanoma and thyroid cancers. We do not find evidence of expression in normal or cancerous human breast. This expression pattern aligns well with RNA-seq data, but contradicts a multitude of studies. Our study highlights how inadequately validated antibodies can lead an exciting field astray.

A large body of work into the role of oestrogen receptor b (ERb) in breast cancer is contradictory, hindering future progress. Here the authors conduct extensive validation of anti-ERb antibodies , and show that normal and cancerous breast tissue do not express ERb, consistent with RNA-seq data.

ERβ1 inhibits metastasis of androgen receptor-positive triple-negative breast cancer by suppressing ZEB1

BACKGROUND

Increasing evidence has indicated an important role for estrogen receptor beta 1 (ERβ1) in breast cancer. However, the role of ERβ1 in the metastasis of androgen receptor (AR)-positive triple-negative breast cancer (TNBC) and the underlying mechanisms are still unknown.

METHODS

Stable ERβ1-expressing TNBC cell lines were generated for this study. We detected the abilities of cell migration and invasion by wound-healing and transwell assays and the expression of E-cadherin and N-cadherin by quantitative RT-PCR (qRT-PCR) and western blotting assays in TNBC cell lines. Chromatin immunoprecipitation (ChIP) analysis was performed to assess the effect of AR on ERβ1 promoter. Tumor metastasis was evaluated in vivo using a lung metastasis mouse model. Lastly, immunohistochemical expression of ERβ1 in TNBC tissues was analyzed and correlated with clinicopathological features.

RESULTS

ERβ1 suppressed the invasion and migration abilities of AR-positive TNBC cells and induced the downregulation of ZEB1. ZEB1 overexpression abrogated the increase in E-cadherin expression and the decrease in N-cadherin expression modulated by ERβ1. A lung metastasis mouse model showed that the incidence of metastasis was lower in ERβ1-expressing TNBC cells. Further, AR activation increased the anti-metastatic effect of ERβ1 in AR-positive TNBC cells, which accelerated ERβ1 transcription by functioning as a transcription factor that bound to the promoter of ERβ1. No significant change was observed in AR expression induced by ERβ1. Immunohistochemistry (IHC) analysis of TNBC clinical samples showed that ERβ1 and AR were positive in 31.7% and 23.2% of samples, respectively. ERβ1 expression was negatively correlated with ZEB1 expression and lymph node metastasis, and positively correlated with the expression of AR and E-cadherin.

CONCLUSION

Our findings suggested a potential role of ERβ1 in metastasis of AR-positive TNBC and provided novel insights into the mechanism of action of ERβ1 and the possible relationship between ERβ1 and AR.

Racial Differences in Adjuvant Endocrine Therapy Use and Discontinuation in Association with Mortality among Medicare Breast Cancer Patients by Receptor Status

Background: There are racial disparities in breast cancer mortality. Our purpose was to determine whether racial/ethnic differences in use and discontinuation of adjuvant endocrine therapy (AET) differed by hormone receptor status and whether discontinuation was associated with mortality.Methods: We conducted a retrospective cohort study with SEER/Medicare dataset of women age ≥65 years diagnosed with stage I-III breast cancer in Medicare Part-D from 2007 to 2009, stratified by hormone receptor status. We performed multivariable logistic regressions to assess racial differences for the odds of AET initiation and Cox proportional hazards models to determine the risk of discontinuation and mortality.Results: Of 14,902 women, 64.5% initiated AET <12 months of diagnosis. Among those with hormone receptor-positive cancer, 74.8% initiated AET compared with 5.6% of women with negative and 54.0% with unknown-receptor status. Blacks were less likely to initiate [OR, 0.76; 95% confidence interval (CI), 0.66-0.88] compared with whites. However, those with hormone receptor-positive disease were less likely to discontinue (HR, 0.89; 95% CI, 0.80-0.98). Women who initiated with aromatase inhibitors had increased risk of discontinuation compared with women who initiated tamoxifen (HR, 1.12; 95% CI, 1.05-1.20). Discontinuation within 12 months was associated with higher risk of all-cause (HR, 1.75; 95% CI, 1.74-2.00) and cancer-specific mortality (HR, 2.76; 95% CI, 1.74-4.38) after controlling for race/ethnicity.Conclusions: There are racial/ethnic differences in AET use and discontinuation. Discontinuing treatment was associated with higher risk of all-cause and cancer-specific mortality regardless of hormone receptor status.Impact: This study underscores the need to study factors that influence discontinuation and the survival benefits of receiving AET for hormone receptor-negative breast cancer. Cancer Epidemiol Biomarkers Prev; 26(8); 1266-75. ©2017 AACR.

A summary of relationships between alternative splicing and breast cancer

Alternative splicing (AS) is the process of combinatorial rearrangement of parts of exons, and/or parts of introns into mature RNA to result in a multitude of transcripts. AS is a biological process through which organisms produce as many protein variants as possible by a limited genetic resource. It plays an important role in growth and development of the organisms. Over the past few years, alternative splicing has been discovered to be critical for genesis and development of malignant tumors, including breast cancer. If the relationships between AS and breast cancer can be discussed more deeply, it will be helpful for better diagnosis, judging prognosis and intervening with breast cancer. In this paper, the relationships between AS and breast cancer are elaborated from different angles, in hope that this summary is beneficial for readers to understand the roles of AS and breast cancer.

Estrogen-Related Factors in the Frontal Lobe of Alzheimer's Disease Patients and Importance of Body Mass Index

Estrogens play a physiologically important role in the brain, but controversies exist regarding the association between Alzheimer’s disease (AD) and estrogens. Estrogen-related factors were comprehensively examined in frontal lobe tissues from autopsied AD patients, and compared with controls. Concentrations of estrogens, expression of estrogen receptors (ERs), and estrogen-metabolizing enzymes (EMEs) which are important for determining the peripheral estrogen concentrations, were examined using liquid chromatography tandem mass spectrometry, immunohistochemistry, and quantitative real-time PCR, respectively. Body mass index (BMI), known to correlate with the serum estrogen concentrations, was also taken into consideration. There were no significant differences in estrogen concentrations or each EME level between the two groups in both the cortex and white matter, whereas glial nuclear ER-β expression was significantly lower in white matter from the AD group than the control group (Allred score, 3.2 ± 0.3 and 6.5 ± 0.3, respectively. P < 0.0001). Estrogen concentrations were found to closely correlate with BMI, particularly in controls. ER-β loss in the white matter from the AD group suggests the necessity of studying the effects of estrogens on glias as well as neurons in the etiology of AD. The correlation between BMI and estrogen concentrations in the frontal lobe suggests the importance of non-brain sources of estrogens.

Energy Balance Modulation Impacts Epigenetic Reprogramming, ERα and ERβ Expression, and Mammary Tumor Development in MMTV-neu Transgenic Mice

The association between obesity and breast cancer risk and prognosis is well established in estrogen receptor (ER)-positive disease but less clear in HER2-positive disease. Here, we report preclinical evidence suggesting weight maintenance through calorie restriction (CR) may limit risk of HER2-positive breast cancer. In female MMTV-HER2/neu transgenic mice, we found that ERα and ERβ expression, mammary tumorigenesis, and survival are energy balance dependent in association with epigenetic reprogramming. Mice were randomized to receive a CR, overweight-inducing, or diet-induced obesity regimen (n = 27/group). Subsets of mice (n = 4/group/time point) were euthanized after 1, 3, and 5 months to characterize diet-dependent metabolic, transcriptional, and epigenetic perturbations. Remaining mice were followed up to 22 months. Relative to the overweight and diet-induced obesity regimens, CR decreased body weight, adiposity, and serum metabolic hormones as expected and also elicited an increase in mammary ERα and ERβ expression. Increased DNA methylation accompanied this pattern, particularly at CpG dinucleotides located within binding or flanking regions for the transcriptional regulator CCCTC-binding factor of ESR1 and ESR2, consistent with sustained transcriptional activation of ERα and ERβ. Mammary expression of the DNA methylation enzyme DNMT1 was stable in CR mice but increased over time in overweight and diet-induced obesity mice, suggesting CR obviates epigenetic alterations concurrent with chronic excess energy intake. In the survival study, CR elicited a significant suppression in spontaneous mammary tumorigenesis. Overall, our findings suggest a mechanistic rationale to prevent or reverse excess body weight as a strategy to reduce HER2-positive breast cancer risk. Cancer Res; 77(9); 2500-11. ©2017 AACR.

Expression of unusual immunohistochemical markers in mucinous breast carcinoma

BACKGROUND

Mucinous breast carcinoma is characterized by the production of variable amounts of mucin. Some studies have addressed immunohistochemical characterization of mucinous breast carcinoma using a limited set of antibodies. However, the purpose of the present study was to investigate a larger panel of markers not widely used in daily practice and to determine their pathological implications.

METHODS

Forty patients diagnosed with mucinous breast carcinoma were enrolled. An immunohistochemical study was performed on whole sections of paraffin embedded tissue, using antibodies for the following markers: estrogen receptor alpha and beta, progesterone receptor, androgen receptor, HER2, EGFR, Ki-67, E-cadherin, β-catenin, p53, chromogranin, synaptophysin, GCDFP15, mammaglobin, and CDX2.

RESULTS

The pure mucinous type was more prevalent in older patients and more frequently expressed GCDFP15. Capella type B presented more frequently with a high Ki-67 index and neuroendocrine differentiation. Although there was a lower frequency of vascular invasion and lymph node metastases in the pure type, the difference was not statistically significant. No case expressed CDX2 (a marker for gastrointestinal tumors), while 85% of the cases expressed at least one of the two typical breast markers (GCDFP15 and mammaglobin), suggesting that these markers may be reliably used for differential diagnosis. Expression of estrogen receptor beta was related to the presence of mucin cell producing lymph node metastasis, with potential prognostic and predictive value.

CONCLUSION

our findings support the immunohistochemical homogeneity of mucinous breast carcinomas because only minor differences were found when subgrouping them into Capella types A and B or into types pure and mixed.

Breast cancer metastasizing to the stomach mimicking primary gastric cancer: A case report

Breast cancer with stomach metastasis rare with an incidence of 1% or less among metastatic breast cancer patients. We experienced a case of breast cancer metastasizing to the stomach in 65-year-old female patient. She experienced dyspepsia and poor oral intake before visiting the clinic. Diffuse infiltration with nodular mucosal thickening of the stomach wall was observed, suggesting advanced gastric cancer based on gross endoscopic finding. Spread of poorly cohesive tumor cells in the gastric mucosa observed upon hematoxylin and eosin stain resembled signet ring cell carcinoma, but diffuse positive staining for GATA3 in immunohistochemical stain allowed for a conclusive diagnosis of breast cancer metastasizing to the stomach. Based on the final diagnosis, systemic chemotherapy was administered instead of primary surgical resection. After 2 cycles of docetaxel administration, she showed a partial response based on abdominal computed tomography scan. This case is an unusual presentation of breast cancer metastasizing to the gastrointestinal tract.

Utility of 18F-fluoroestradiol (18F-FES) PET/CT imaging as a pharmacodynamic marker in patients with refractory estrogen receptor-positive solid tumors receiving Z-endoxifen therapy

BACKGROUND

Z-endoxifen is the most potent of the metabolites of tamoxifen, and has the potential to be more effective than tamoxifen because it bypasses potential drug resistance mechanisms attributable to patient variability in the expression of the hepatic microsomal enzyme CYP2D6. 18F-FES is a positron emission tomography (PET) imaging agent which selectively binds to estrogen receptor alpha (ER-α) and has been used for non-invasive in vivo assessment of ER activity in tumors. This study utilizes 18F-FES PET imaging as a pharmacodynamic biomarker in patients with ER+ tumors treated with Z-endoxifen.

METHODS

Fifteen patients were recruited from a parent therapeutic trial of Z-endoxifen and underwent imaging with 18F-FES PET at baseline. Eight had positive lesions on the baseline scan and underwent follow-up imaging with 18F-FES 1-5 days post administration of Z-endoxifen.

RESULTS

Statistically significant changes (p = 0.0078) in standard uptake value (SUV)-Max were observed between the baseline and follow-up scans as early as 1 day post drug administration.

CONCLUSION

F-FES PET imaging could serve as a pharmacodynamic biomarker for patients treated with ER-directed therapy.

[Androgen receptors in breast cancer: Expression, value and therapeutic prospects]

Triple-negative (TN) breast cancer are characterized by lack of estrogen receptor (OR) and progesterone receptor (PR) expression, and the absence of overexpression of human epidermal growth factor receptor 2 (HER2). It is a heterogeneous group of tumors with a more pejorative prognosis than other subtypes of breast cancer. Androgen receptors (AR) are nuclear receptors whose expression varies from 80 to 85% of primary breast cancers and 60 to 75% of metastatic cancers. Among the TN breast cancers, the luminal androgen receptor (LAR) subtype expresses AR more frequently, up to 53% of the cases. AR are associated with lower tumor size, histological grade, Ki67, and lymph node involvement. The results of recent clinical trials evaluating anti-androgen therapies in locally advanced or metastatic TN breast cancer are promising. Many new therapies are tested, including enzalutamide or abiraterone acetate, and numerous therapeutic combinations including PI3K/AKT/mTOR inhibitors or CDK inhibitors. These therapies would allow an alternative treatment of patients with TN breast cancer for which there is often a therapeutic impasse.

Regulation of submaxillary gland androgen-regulated protein 3A via estrogen receptor 2 in radioresistant head and neck squamous cell carcinoma cells

Background

Molecular mechanisms of intrinsic or acquired radioresistance serve as critical barrier for curative therapy of head and neck squamous cell carcinoma (HNSCC) and remain a major obstacle for progression-free and disease-specific survival.

Methods

HNSCC cell lines were treated with a protocol of fractionated irradiation (IR, 4× 2Gy) alone or in combination with antagonists of estrogen receptor signaling and viability was determined by a colony-forming assay (CFA). Expression of submaxillary gland androgen-regulated protein 3A (SMR3A) and estrogen receptor 2 (ESR2) were assessed in tumor cells in vitro by RQ-PCR, Western blot analysis and immunofluorescence staining, and by immunohistochemical staining of tissue microarrays containing tumor sections from patients with oropharyngeal squamous cell carcinoma (OPSCC), which were treated by definitive or adjuvant radiotherapy. Subgroups with distinct SMR3A and ESR2 expression patterns were correlated with clinical parameters and survival outcome including multivariable analysis.

Results

Fractionated irradiation (IR) revealed an accumulation of tumor cells with prominent SMR3A expression, which was accompanied by an up-regulation of the estrogen receptor 2 (ESR2). ESR2-dependent regulation of SMR3A was supported by induced expression after stimulation with estradiol (E2), which was impaired by co-treatment with 4-Hydroxytamoxifen (TAM) or Fulvestrant, respectively. Both drugs significantly sensitized FaDu cells to fractionated IR as determined by a CFA and accelerated apoptosis. These data suggest a critical role of ESR2 in radioresistance and that SMR3A might serve as a surrogate marker for active ESR2 signaling. In line with this assumption, ESR2-positive oropharyngeal squamous cell carcinoma (OPSCC) with high SMR3A expression had an unfavorable progression-free and disease-specific survival as compared to those tumors with low SMR3A expression.

Conclusions

In summary, our findings provide compelling experimental evidence that HNSCC with SMR3A and ESR2 co-expression have a higher risk for treatment failure and these patients might benefit from clinically well-established drugs targeting estrogen receptor signaling.

Electronic supplementary material

The online version of this article (doi:10.1186/s13046-017-0496-2) contains supplementary material, which is available to authorized users.

High Estrogen Receptor β Expression Is Prognostic among Adjuvant Chemotherapy-Treated Patients-Results from a Population-Based Breast Cancer Cohort

PURPOSE

Isoform-specific tumor estrogen receptor β (ERβ) expression may hold prognostic information in breast cancer, especially among endocrine-treated breast cancer patients. The study's purpose was to evaluate ERβ isoform 1 (ERβ1) expression in relation to tumor characteristics, ESR2 genotypes, and prognosis in different treatment groups.

EXPERIMENTAL DESIGN

A population-based prospective cohort of 1,026 patients diagnosed with primary invasive breast cancer in Lund, Sweden, between October 2002 and June 2012 was followed until June 2014 (median 5 years). Associations between immunohistochemical ERβ1 expression, patient and tumor characteristics, as well as outcome within treatment groups were analyzed.

RESULTS

Tumor ERβ1 expression was available for 911 patients (89%) and was not associated with ESR2 genotypes. ERβ1 positivity, defined as >75% (ERβ1₇₅⁺, 72.7%), was positively associated with established favorable tumor characteristics. Overall, ERβ1₇₅⁺ was associated with lower risk of breast cancer events [HR_adj = 0.60; 95% confidence interval (CI), 0.41-0.89]. The magnitude of the association was larger in patients with ERα^- tumors (HR_adj = 0.30; 95% CI, 0.12-0.76), compared with ERα⁺ tumors (HR_adj = 0.66; 95% CI, 0.42-1.03). Among the 232 chemotherapy-treated patients, ERβ1₇₅⁺ tumors were associated with lower risk of breast cancer events compared with ERβ1₇₅^- tumors (HR_adj = 0.31; 95% CI, 0.15-0.64). Among the 671 chemonaïve patients, ERβ1₇₅ status was not associated with the outcome.

CONCLUSIONS

High ERβ1 expression was a favorable prognostic marker in this breast cancer cohort, especially in chemotherapy-treated patients, but not in endocrine therapy-treated patients. These results warrant confirmation, preferably via a biomarker study in a previously conducted randomized trial. Clin Cancer Res; 23(3); 766-77. ©2016 AACR.

Estrogen signaling and unfolded protein response in breast cancer

Activation of the unfolded protein response (UPR) confers resistance to anti-estrogens and chemotherapeutics in estrogen receptor α (ERα)-positive and triple-negative breast cancers. Among the regulators of the UPR in breast cancer is estrogen signaling. Estrogen regulates major components of the UPR and ER expression is associated with the sensitivity of tumor cells to UPR-regulated apoptosis. Recent studies have confirmed the crosstalk between the ERs and UPR and suggest novel therapeutic strategies that combine targeting of both signaling pathways. These remedies may be more effective in repressing oncogenic adaptive mechanisms and benefit patients with resistant disease.

Recent perspectives of breast cancer prognosis and predictive factors

Breast cancer is the most common type of cancer affecting women worldwide. Although there have been great improvements in treating the disease and at present between 80 and 90% of the women survive ≥5-years after their primary diagnosis. However, due to the high incidence of the disease >450,000 women succumb to breast cancer annually worldwide. The majority of improvements in breast cancer survival may be explained through better knowledge of the development and progression of the disease. Consequently, the treatments employed have become more effective. Furthermore, continuous efforts are being made for the identification of novel and efficient biomarkers for the timely prognosis of breast cancer. The present review aims to examine recent perspectives of breast cancer prognosis and the predictive factors involved.

Nuclear estrogen receptor-α expression is an independent predictor of recurrence in male patients with pT1aN0 lung adenocarcinomas, and correlates with regulatory T-cell infiltration

Background

Tumor biology of estrogen receptor-α (ERα) and progesterone receptor (PR) has been studied in breast cancers. However, clinical impact in lung cancer remains controversial. In our study, we investigate whether ERα and PR expression predicts disease recurrence and correlates with immunologic factors in stage I lung adenocarcinoma.

Methods

We reviewed patients with pathologic stage I resected lung adenocarcinoma. Tumors were classified according to the IASLC/ATS/ERS classification. Immunostaining of ERα and PR was performed using tissue microarrays (n = 913). Immunostaining of CD3+ and forkhead box P3 (FoxP3)+ lymphocyte infiltration, interleukin-7 receptor (IL-7R), and IL-12Rβ2 were performed. Cumulative incidence of recurrence (CIR) analysis was used to estimate probability of recurrence.

Results

Nuclear ERα expression was observed in 157 (17%) patients and presented more frequently in females (P = 0.038) and smaller tumors (P = 0.019). Nuclear ERα expression was not identified in mucinous tumors. In pT1a patients, 5-year CIR of patients with ERα-positive tumors was significantly higher (5-year CIR, 20%) than those with ERα-negative tumors (8%; P = 0.018). This difference was statistically significant in males (P = 0.003) but not females (P = 0.55). On multivariate analysis, nuclear ERα expression was an independent predictor of recurrence (hazard ratio = 2.27; P = 0.030). In pT1a patients, nuclear ERα expression positively correlated with tumoral FoxP3+ lymphocytes (P < 0.001), FoxP3/CD3 index (P < 0.001), and IL-7R (P = 0.022).

Conclusions

Nuclear ERα expression is an independent predictor of recurrence in pT1a lung adenocarcinomas and correlates with poor prognostic immune microenvironments.

How far have we come in terms of estrogens in breast cancer? [Review]

Major advances in breast cancer treatment have almost always been linked to the actions of estrogen. Therefore, this review focused on estrogen actions in the breast, particularly the developments of the past 20 years, the present understanding of disease biology and possible future developments. Within these areas have focused on what is known about the underlying molecular biology and in particular integration of the bioinformatics revolution of the last 15 years with other facets of research. In addition, there will be an emphasis on the understanding brought about by a greater appreciation for the intracrinology of the breast.

Targeting Estrogen Receptor Beta in a Phase 2 Study of High-Dose Estradiol in Metastatic Triple-Negative Breast Cancer: A Wisconsin Oncology Network Study

BACKGROUND

Estrogen receptor beta (ERβ) is expressed by 50% to 80% of triple-negative breast cancers (TNBC). Agonism of ERβ has antiproliferative effects in TNBC cells expressing ERβ. This phase 2 study evaluated single-agent high-dose estradiol in patients with advanced TNBC.

PATIENTS AND METHODS

Adult women with measurable advanced TNBC were treated with estradiol 10 mg oral 3 times daily provided continuously for 28-day cycles. A Simon optimal 2-stage design was used. The primary end point was objective response (OR). Secondary end points included progression-free survival (PFS), clinical benefit (CB), and safety. OR, CB, and PFS by ERβ status were also examined.

RESULTS

Seventeen evaluable women were enrolled. Median age was 58 years (range, 34-90 years); the median number of prior systemic therapies was 2 (range, 0-6). One patient had a confirmed partial response (OR rate, 5.9%) and remained on the study for > 24 weeks. Three patients had stable disease, with one lasting more than 16 weeks. ERβ expression was detected in 77% (13 patients). The CB rate at 16 weeks was 15% (2 of 13) in ERβ-positive patients and 0% (0 of 4) in ERβ-negative patients (P = 1). PFS was poor (median, 1.9 months) and not statistically significantly different between ERβ-positive versus -negative patients. No new adverse events from estradiol were identified. The study closed after the first stage as a result of limited responses in these unselected patients.

CONCLUSION

In unselected TNBC, high-dose estradiol has limited efficacy. However, further evaluation of ERβ selective agonists in TNBC selected by ERβ expression may be warranted.

Estrogen receptor beta as a prognostic factor in breast cancer patients: A systematic review and meta-analysis

BACKGROUND

The prognostic role of estrogen receptor beta (ERβ) in early-stage breast cancer is unclear. We performed a systematic review and meta-analysis to evaluate the prognostic value of ERβ in early-stage breast cancer patients.

METHOD

We searched Medline, Embase, and the Web of Science for studies published between 1990 and 2015 that assessed ERβ status in breast cancer patients. A total of 25 studies comprising 9919 patients fitting our inclusion and exclusion criteria were included. The hazard ratios of ERβ status were extracted for diseases free survival (DFS)/ ) and overall survival (OS). Random or fixed-effects models were used when appropriate, and between-study heterogeneity was assessed.

RESULTS

In the 20 studies that assessed ERβ status using immunohistochemical (IHC) methods, we observed significantly improved DFS in patients positive for ERβ-1 (HR=0.56, 95%CI 0.40-0.78, P=0.0007) and ERβ-2 (HR=0.67, 95%CI 0.45-1.00, P=0.05). Improved OS was associated with a positive status for pan-ERβ (HR=0.60, 95%CI 0.45-0.80, P=0.0004) and ERβ-2 (HR=0.44, 95%CI 0.31-0.62, P<0.0001). In ERα-positive patients, ERβ positivity was not associated with DFS (HR=0.77, 95%CI 0.46-1.27, P=0.31) or OS (HR=0.64, 95%CI 0.37-1.11, P=0.11). In contrast, ERβ expression was significantly associated with increased DFS (HR=0.37, 95%CI 0.14-0.93, P=0.03) or OS (HR=0.44, 95%CI 0.30-0.65, P<0.0001) in ERα-negative patients. We did not observe an association between ERβ mRNA levels and DFS and OS.

CONCLUSION

In this study, we showed that IHC ERβ status, rather than mRNA levels, is a prognostic factor that is associated with DFS and OS in breast cancer patients. The prognostic value of ERβ may be higher in ERα-negative patients than in ERα-positive patients.

The gender differences in the inhibitory action of UVB-induced melanocyte activation by the administration of tranexamic acid

BACKGROUND

Tranexamic acid has an inhibitory action on ultraviolet (UV) B-induced melanocyte activation. This study examined the sex differences in the inhibitory action of tranexamic acid on UVB-induced melanocyte activation.

METHODS

We irradiated the eye and ear of male and female mice with UVB at a dose of 1.0 kJ/m(2) using a 20SE sunlamp. We orally administered tranexamic acid (750 mg/kg/day) at 30 min before UVB exposure.

RESULTS

Tranexamic acid inhibited the UVB-induced epidermal melanocyte activation, and the effect was more remarkable under UVB eye irradiation than under UVB ear irradiation. Furthermore, the melanocyte activity suppression effect was stronger in female mice than in male mice. Following the administration of tranexamic acid, the female displayed increased blood levels of β-endorphin and μ-opioid receptor and estradiol receptor β expression in comparison with the male. Furthermore, the effect of melanocyte activity suppression in the female mice was decreased by the administration of tamoxifen (antagonist of estrogen receptor) or naltrexone (antagonist of μ-opioid receptor).

CONCLUSIONS

These results suggest that the suppression by tranexamic acid of the UVB-induced melanocyte activation (UVB sensitivity) is stronger in female mice than in male mice and that female hormones and β-endorphin play an important role in this sex difference.

Targeting Androgen/Estrogen Receptors Crosstalk in Cancer

The actions of estrogens are mediated by estrogen receptors, ERα and ERβ. Recent genomic landscaping of ERα- and ERβ-binding sites has revealed important distinctions regarding their transcriptional activity. ERβ and its isoforms have been correlated with endocrine treatment responsiveness in breast tumors, while post-translational modifications, receptor dimerization patterns, and subcellular localization are increasingly recognized as crucial modulators in prostate carcinogenesis. Androgen receptor (AR) is essential for the development and progression of prostate cancer as well as of certain breast cancer types. The balance between the activity of these two hormone receptors and their molecular interactions in different clinical settings is influenced by several coregulators. This comprises a dynamic regulatory network enhancing or limiting the activity of AR-directed treatments in breast and prostate tumorigenesis. In this review, we discuss the molecular background regarding the therapeutic targeting of androgen/estrogen receptor crosstalk in breast and prostate cancer.

Obesity Suppresses Estrogen Receptor Beta Expression in Breast Cancer Cells via a HER2-Mediated Pathway

Obesity is associated with a worse breast cancer prognosis, while greater breast tumor estrogen receptor beta (ERβ) expression is correlated with improved therapy response and survival. The objective of this study was to determine the impact of obesity on breast cancer cell ERβ expression, which is currently unknown. We utilized an in vitro model of obesity in which breast cancer cells were exposed to patient serum pooled by body mass index category (obese (OB): ≥30 kg/m2; normal weight (N): 18.5-24.9 kg/m2). Four human mammary tumor cell lines representing the major breast cancer subtypes (SKBR3, MCF-7, ZR75, MDA-MB-231) and mammary tumor cells from MMTV-neu mice were used. ERβ expression, assessed by qPCR and western blotting, was suppressed in the two HER2-overexpressing cell lines (SKBR3, MMTV-neu) following OB versus N sera exposure, but did not vary in the other cell lines. Expression of Bcl-2 and cyclin D1, two genes negatively regulated by ERβ, was elevated in SKBR3 cells following exposure to OB versus N sera, but this difference was eliminated when the ERβ gene was silenced with siRNA. Herceptin, a HER2 antagonist, and siRNA to HER2 were used to evaluate the role of HER2 in sera-induced ERβ modulation. SKBR3 cell treatment with OB sera plus Herceptin increased ERβ expression three-fold. Similar results were obtained when HER2 expression was silenced with siRNA. OB sera also promoted greater SKBR3 cell viability and growth, but this variance was not present when ERβ was silenced or the cells were modified to overexpress ERβ. Based on this data, we conclude that obesity-associated systemic factors suppress ERβ expression in breast cancer cells via a HER2-mediated pathway, leading to greater cell viability and growth. Elucidation of the mechanism(s) mediating this effect could provide important insights into how ERβ expression is regulated as well as how obesity promotes a more aggressive disease.

Aberrant Splicing of Estrogen Receptor, HER2, and CD44 Genes in Breast Cancer

Breast cancer (BC) is the most common cause of cancer-related death among women under the age of 50 years. Established biomarkers, such as hormone receptors (estrogen receptor [ER]/progesterone receptor) and human epidermal growth factor receptor 2 (HER2), play significant roles in the selection of patients for endocrine and trastuzumab therapies. However, the initial treatment response is often followed by tumor relapse with intrinsic resistance to the first-line therapy, so it has been expected to identify novel molecular markers to improve the survival and quality of life of patients. Alternative splicing of pre-messenger RNAs is a ubiquitous and flexible mechanism for the control of gene expression in mammalian cells. It provides cells with the opportunity to create protein isoforms with different, even opposing, functions from a single genomic locus. Aberrant alternative splicing is very common in cancer where emerging tumor cells take advantage of this flexibility to produce proteins that promote cell growth and survival. While a number of splicing alterations have been reported in human cancers, we focus on aberrant splicing of ER, HER2, and CD44 genes from the viewpoint of BC development. ERα36, a splice variant from the ER1 locus, governs nongenomic membrane signaling pathways triggered by estrogen and confers 4-hydroxytamoxifen resistance in BC therapy. The alternative spliced isoform of HER2 lacking exon 20 (Δ16HER2) has been reported in human BC; this isoform is associated with transforming ability than the wild-type HER2 and recapitulates the phenotypes of endocrine therapy-resistant BC. Although both CD44 splice isoforms (CD44s, CD44v) play essential roles in BC development, CD44v is more associated with those with favorable prognosis, such as luminal A subtype, while CD44s is linked to those with poor prognosis, such as HER2 or basal cell subtypes that are often metastatic. Hence, the detection of splice variants from these loci will provide keys to understand the pathogenesis, predict the prognosis, and choose specific therapies for BC.

Differences in clinical importance of Bcl-2 in breast cancer according to hormone receptors status or adjuvant endocrine therapy

BACKGROUND

Bcl-2 plays an anti-apoptotic role, resulting in poor clinical outcome or resistance to therapy in most tumor types expressing Bcl-2. In breast cancer, however, Bcl-2 expression has been reported to be a favorable prognostic factor. The positive correlation of Bcl-2 with estrogen receptor (ER)/progesterone receptor (PR) status, and endocrine therapy frequently given for hormone receptor-positive tumors, may obscure the independent pathobiological role of Bcl-2. We constructed a large systematic study to determine whether Bcl-2 has an independent role in breast cancer.

METHODS

Bcl-2 expression was immunohistochemically evaluated and compared with other clinicopathological factors, including clinical outcome, in 1081 breast cancer cases with long follow-up, separately analyzing 634 cases without any adjuvant therapy and 447 cases with tamoxifen monotherapy. The χ (2)-test for independence using a contingency table, the Kaplan-Meier method with the log-rank test, and a Cox proportional hazards model were used for the comparison of clinicopathological factors, assessment of clinical outcome, and multivariate analyses, respectively.

RESULTS

In both patient groups, Bcl-2 expression strongly correlated with positive ER/PR status, low grade, negative human epidermal growth factor receptor 2 (HER2) status, and small tumor size, as previously reported. Bcl-2 expression did not independently predict clinical outcome in patients with ER-positive and/or PR-positive tumors or in those who received tamoxifen treatment; however, it was an independent unfavorable prognostic factor in patients with ER-negative/PR-negative or triple-negative (ER-negative/PR-negative/HER2-negative) tumors who received no adjuvant therapy. The latter was even more evident in postmenopausal women: those with hormone receptor-negative or triple-negative tumors lacking Bcl-2 expression showed a favorable outcome.

CONCLUSION

Bcl-2 expression is an independent poor prognostic factor in patients with hormone receptor-negative or triple-negative breast cancers, especially in the absence of adjuvant therapy, suggesting that the anti-apoptotic effect of Bcl-2 is clearly exhibited under such conditions. The prognostic value of Bcl-2 was more evident in postmenopausal women. The present findings also highlight Bcl-2 as a potential therapeutic target in breast cancers lacking conventional therapeutic targets such as triple-negative tumors. The favorable prognosis previously associated with Bcl-2-positive breast cancer probably reflects the indirect effect of frequently coexpressed hormone receptors and adjuvant endocrine therapy.

Autocrine interferon-γ may affect malignant behavior and sensitivity to tamoxifen of MCF-7 via estrogen receptor β subtype

Mitogenic actions of estrogens are mediated by two distinct estrogen receptors (ERs), which are critical in the progression and therapeutic response of breast cancer. ER expression is a dynamic phenomenon that is regulated by numerous factors, including cytokines, in the tumor microenvironment. Recently, studies have shown that autocrine production of IL-4 promotes cancer cell growth and there is negative correlation between tumor IL-4 and hormone receptor levels, suggesting that there is crosstalk between cytokine receptors and ER. Thus, we evaluated for interaction between the two ERs and the cytokines IL-4 and IFN-γ, and if this interaction modulates malignant behavior. We identified that ERβ exerts protective activity in the progression of breast cancer cell line MCF-7, which co-expresses ERα and ERβ. IFN-γ and IL-4 have the opposite effects on malignant biological behavior. Furthermore, we found positive correlation between IFN-γ and ERβ expression in MCF-7. We also determined that autocrine IFN-γ in MCF-7 increases mRNA expression of ERβ resulting in enhanced sensitivity to tamoxifen (TAM). These results indicate that ERβ and autocrine IFN-γ represent two putative targets for breast cancer therapy.

Estrogen receptor mutations and functional consequences for breast cancer

A significant number of estrogen receptor α (ERα)-positive breast tumors develop resistance to endocrine therapy and recur with metastatic disease. Several mechanisms of endocrine resistance have been proposed, including genetic alterations that lead to ERs with altered protein sequence. By altering the conformation of the protein and increasing the interaction with coactivators, point mutations in ESR1, the gene encoding ERα, promote an active form of the receptor in the absence of hormone that assists tumor cells to evade hormonal treatments. Recent studies have confirmed that ESR1 point mutations frequently occur in metastatic breast tumors that are refractory to endocrine therapy, and suggest the development of novel strategies that may be more effective in controlling ER signaling and benefit patients with recurrent and metastatic disease.

Prognostic and predictive value of ERβ1 and ERβ2 in the Intergroup Exemestane Study (IES)-first results from PathIES†

BACKGROUND

Intergroup Exemestane Study (IES) was a randomised study that showed a survival benefit of switching adjuvant endocrine therapy after 2-3 years from tamoxifen to exemestane. PathIES aimed to assess the potential prognostic and predictive value of ERβ1 and ERβ2 expression in primary tumours in order to determine benefit in the two treatment arms.

PATIENTS AND METHODS

Primary tumour samples were available for 1256 patients (27% IES population). ERβ1 and ERβ2 expression was dichotomised at the median IHC score (high if ERβ1 ≥ 191, ERβ2 ≥ 164). Hazard ratios (HRs) were estimated by multivariable Cox proportional hazards models adjusting for clinicopathological factors. Treatment effects with biomarker expressions were determined by interaction tests. Analysis explored effects of markers both as a continuous variable and with dichotomised cut-offs.

RESULTS

Neither ERβ1 nor ERβ2 were associated with disease-free survival (DFS) or overall survival (OS) in the whole cohort. In patients treated with continued tamoxifen, high ERβ1 expression compared with low was associated with better DFS [HR = 0.38:95% confidence interval (CI) 0.21-0.68, P = 0.001]. DFS benefit of exemestane over tamoxifen (HR = 0.40:95% CI 0.22-0.70) was found in the low ERβ1 subgroup (interaction P = 0.01). No significant difference with treatment was observed for ERβ2 expression in either DFS or OS.

CONCLUSION

In the PathIES population, exemestane appeared to be superior to tamoxifen among patients with low ERβ1 expression but not in those with high ERβ1 expression. This is the first trial of its kind to report a parameter potentially predicting benefit of an aromatase inhibitor when compared with tamoxifen and an independent validation is warranted.

ERβ expression and breast cancer risk prediction for women with atypias

Estrogen receptor (ER) β is highly expressed in normal breast epithelium and a putative tumor suppressor. Atypical hyperplasia substantially increases breast cancer risk, but identification of biomarkers to further improve risk stratification is needed. We evaluated ERβ expression in breast tissues from women with atypical hyperplasia and association with subsequent breast cancer risk. ERβ expression was examined by immunohistochemistry in a well-characterized 171-women cohort with atypical hyperplasia diagnosed 1967-1991. Nuclear ERβ percent and intensity was scored in the atypia and adjacent normal lobules. An ERβ sum score (percent + intensity) was calculated and grouped as low, moderate, or high. Competing risks regression was used to assess associations of ERβ expression with breast cancer risk. After 15-year median follow-up, 36 women developed breast cancer. ERβ expression was lower in atypia lobules in than normal lobules, by percent staining and intensity (both P < 0.001). Higher ERβ expression in the atypia or normal lobules, evaluated by percent staining, intensity or sum score, decreased the risk of subsequent breast cancer by 2-fold (P = 0.04) and 2.5-fold (P = 0.006). High normal lobule ERβ expression conferred the strongest protective effect in premenopausal women: the 20-year cumulative incidence of breast cancer was 0% for women younger than 45 years with high versus 31% for low-moderate ERβ expression (P = 0.0008). High ERβ expression was associated with a significantly decreased risk of breast cancer in women with atypical hyperplasia. These data suggest that ERβ may be a useful biomarker for risk stratification and a novel therapeutic target for breast cancer risk reduction.

Estrogen and cancers of the colorectum, breast, and lung in postmenopausal women

As estrogens play an important role in maintaining physiological function in various organs, the estrogen decrease after menopause is thought to cause various diseases frequently observed in postmenopausal or elderly women. With the aging of society and a decrease in infectious or vascular diseases, neoplasms have now become the most frequent cause of death in Japan. Cancers of the colorectum, breast, and lung have been rapidly increasing both in incidence and death, especially among postmenopausal women. Interestingly, all three of these cancers are associated with estrogens. In premenopausal women, ovarian estrogens plays major roles in the female reproductive organs through the classic estrogen receptor, ER-α. In postmenopausal women, however, estrogens produced/activated by peripherally localized estrogen-metabolizing enzymes such as aromatase, which converts androgen into estrogens, are thought to play physiologically and pathobiologically important roles in various organs through second ER, namely ER-β, distributing systemically. In this article, the association of estrogens with these cancers in postmenopausal or elderly women are reviewed, especially focusing on the role of ER-β and peripheral estrogen metabolism. The possibility of prevention or treatment of these diseases through estrogenic control is also discussed.

Unfolding the Role of Stress Response Signaling in Endocrine Resistant Breast Cancers

The unfolded protein response (UPR) is an ancient stress response that enables a cell to manage the energetic stress that accompanies protein folding. There has been a significant recent increase in our understanding of the UPR, how it integrates physiological processes within cells, and how this integration can affect cancer cells and cell fate decisions. Recent publications have highlighted the role of UPR signaling components on mediating various cell survival pathways, cellular metabolism and bioenergenics, and autophagy. We address the role of UPR on mediating endocrine therapy resistance and estrogen receptor-positive breast cancer cell survival.

ERβ1 inversely correlates with PTEN/PI3K/AKT pathway and predicts a favorable prognosis in triple-negative breast cancer

In contrast to the well-established role of estrogen receptor alpha (ERα) in breast cancer, the significance of estrogen receptor beta (ERβ) remains controversial, especially in triple-negative breast cancer (TNBC). We sought to investigate the clinical importance of wild-type ERβ (ERβ1) in TNBC based on a large population, and to explore the potential molecular pathways involved in. A total of 571 patients with invasive TNBC undergoing curative surgery were included in this study. Immunohistochemical staining for ERβ1, pAKT, PTEN, pERK, β-catenin, EGFR, p53, and E-cadherin was performed on tissue microarrays. Prognostic determinants for overall survival (OS) and disease-free survival (DFS), as well as the risk factors for distant metastasis-free survival (DMFS) and locoregional recurrence-free survival, were evaluated in univariate and multivariate analyses. Overexpression of ERβ1 was detected in 30.4% of tumor samples. Patients with ERβ1 tended to be postmenopausal, and less likely to develop lymphatic metastasis. Multivariate analysis demonstrated that ERβ1 predicted a better OS, DFS, and DMFS independently. Regarding other biomarkers, only pAKT was identified as an independent negative predictor for survival. Additionally, ERβ1 expression was inversely associated with pAKT and the loss of PTEN. Notably, further survival analysis according to status of ERβ1/pAKT indicated that ERβ1(+)/pAKT(-) predicted the most favorable prognosis for TNBC. On the contrary, ERβ1(-)/pAKT(+) was associated with the worst outcomes. In summary, our findings indicate that ERβ1 independently predicts a better prognosis for TNBC and potentially interacts with the PTEN/PI3K/pAKT pathway. The role of ERβ1-specific agonists combined with the inhibitors of pAKT merits further investigation.

Combination therapy with anti-DR5 antibody and tamoxifen for triple negative breast cancer

TRA-8, a monoclonal antibody targeting death receptor, has demonstrated high therapeutic effect for triple negative breast cancer (TNBC) in preclinical models. Tamoxifen, the standard of care for ERα-positive breast cancer, induces apoptosis via ERβ, which commonly presents in TNBC cells. The current study investigates the combination effects of TRA-8 and tamoxifen for TNBC. In vitro assays were implemented with two ERβ-positive TNBC cell lines, SUM159 and 2LMP, and in vivo therapy studies were followed using orthotopic breast tumor mouse models. IC50 of tamoxifen for SUM159 and 2LMP were 29 μM and 38 μM, respectively. Synergy between TRA-8 (0-1000 ng/mL) and tamoxifen (20 μM) was observed for both the cell lines. Tamoxifen (400 mg/kg diet) markedly suppressed the growth of SUM159 tumors for 6 weeks after therapy initiation, but it did not induce antitumor effect for 2LMP tumors. TRA-8 (0.1 mg, weekly, i.p.) successfully arrested the growth of both SUM159 and 2LMP tumors during therapy, but an antagonistic effect was observed when tamoxifen was combined. TRA-8 uptake into tumors was not changed by tamoxifen treatment. Histological analysis confirmed that caspase-3 activation induced by TRA-8 was significantly decreased when tamoxifen was used in combination. In conclusion, our findings suggest that the combined use of TRA-8 and tamoxifen may cause antagonistic effects for TNBC patients.

Estrogen receptor beta impacts hormone-induced alternative mRNA splicing in breast cancer cells

BACKGROUND

Estrogens play an important role in breast cancer (BC) development and progression; when the two isoforms of the estrogen receptor (ERα and ERβ) are co-expressed each of them mediate specific effects of these hormones in BC cells. ERβ has been suggested to exert an antagonist role toward the oncogenic activities of ERα, and for this reason it is considered an oncosuppressor. As clinical evidence regarding a prognostic role for this receptor subtype in hormone-responsive BC is still limited and conflicting, more knowledge is required on the biological functions of ERβ in cancer cells. We have previously described the ERβ and ERα interactomes from BC cells, identifying specific and distinct patterns of protein interactions for the two receptors. In particular, we identified factors involved in mRNA splicing and maturation as important components of both ERα and ERβ pathways. Guided by these findings, here we performed RNA sequencing to investigate in depth the differences in the early transcriptional events and RNA splicing patterns induced by estradiol in cells expressing ERα alone or ERα and ERβ.

RESULTS

Exon skipping was the most abundant splicing event in the post-transcriptional regulation by estradiol. We identified several splicing events induced by ERα alone and by ERα+ERβ, demonstrating for the first time that ERβ significantly affects estrogen-induced splicing in BC cells, as revealed by modification of a subset of ERα-dependent splicing by ERβ, as well as by the presence of splicing isoforms only in ERβ+cells. In particular, we observed that ERβ+BC cell lines exhibited around 2-fold more splicing events than the ERβ- cells. Interestingly, we identified putative direct targets of ERβ-mediated alternative splicing by correlating the genomic locations of ERβ and ERα binding sites with estradiol-induced differential splicing in the corresponding genes.

CONCLUSIONS

Taken together, these results demonstrate that ERβ significantly affects estrogen-induced early transcription and mRNA splicing in hormone-responsive BC cells, providing novel information on the biological role of ERβ in these tumors.

Is androgen receptor targeting an emerging treatment strategy for triple negative breast cancer?

Triple negative breast cancer (TNBC) is an aggressive breast cancer subtype. The absence of expression and/or amplification of estrogen and progesterone receptor as well as ERBB-2 prevent the use of currently available endocrine options and/or ERBB-2-directed drugs and indicates chemotherapy as the main current therapy. TNBC represents approximately 15% of breast cancer cases with high index of heterogeneity. Here, we review the role of androgen receptor in breast carcinogenesis and its association with alterations in the expression pattern and functional roles of regulatory molecules and signal transduction pathways in TNBC. Additionally, based on the so far preclinical and clinical published data, we evaluate the perspectives for using and/or developing androgen receptor targeting strategies for specific TNBC subtypes.

Involvement of multiple cellular pathways in regulating resistance to tamoxifen in BIK-suppressed MCF-7 cells

Majority of women with estrogen receptor (ER)-positive breast cancers initially respond to hormone therapies such as tamoxifen (TAM; antagonist of estrogen). However, many tumors eventually become resistant to TAM. Therefore, understanding the various cellular components involved in causing resistance to TAM is of paramount importance in designing novel entities for efficacious hormone therapy. Previously, we found that suppression of BIK gene expression induced TAM resistance in MCF-7 breast cancer cells. In order to understand the response of these cells to TAM and its association with resistance, a microarray analysis of gene expression was performed in the BIK-suppressed MCF-7 cells and compared it to the TAM-only-treated cells (controls). Several genes participating in various cellular pathways were identified. Molecules identified in the drug resistance pathway were 14-3-3z or YWHAZ, WEE1, PRKACA, NADK, and HSP90AA 1. Further, genes involved in cell cycle control, apoptosis, and cell proliferation were also found differentially expressed in these cells. Transcriptional and translational analysis of key molecules such as STAT2, AKT 3, and 14-3-3z revealed similar changes at the messenger RNA (mRNA) as well as at the protein level. Importantly, there was no cytotoxic effect of TAM on BIK-suppressed MCF-7 cells. Further, these cells were not arrested at the G0-G1 phase of the cell cycle although 30 % of BIK-suppressed cells were arrested at the G2 phase of the cycle on TAM treatment. Furthermore, we found a relevant interaction between 14-3-3z and WEE1, suggesting that the cytotoxic effect of TAM was prevented in BIK-suppressed cells because this interaction leads to transitory arrest in the G2 phase leading to the repair of damaged DNA and allowing the cells to proliferate.

Biologic roles of estrogen receptor-β and insulin-like growth factor-2 in triple-negative breast cancer

Triple-negative breast cancer (TNBC) occurs in 10–15% of patients yet accounts for almost half of all breast cancer deaths. TNBCs lack expression of estrogen and progesterone receptors and HER-2 overexpression and cannot be treated with current targeted therapies. TNBCs often occur in African American and younger women. Although initially responsive to some chemotherapies, TNBCs tend to relapse and metastasize. Thus, it is critical to find new therapeutic targets. A second ER gene product, termed ERβ, in the absence of ERα may be such a target. Using human TNBC specimens with known clinical outcomes to assess ERβ expression, we find that ERβ1 associates with significantly worse 5-year overall survival. Further, a panel of TNBC cell lines exhibit significant levels of ERβ protein. To assess ERβ effects on proliferation, ERβ expression in TNBC cells was silenced using shRNA, resulting in a significant reduction in TNBC proliferation. ERβ-specific antagonists similarly suppressed TNBC growth. Growth-stimulating effects of ERβ may be due in part to downstream actions that promote VEGF, amphiregulin, and Wnt-10b secretion, other factors associated with tumor promotion. In vivo, insulin-like growth factor-2 (IGF-2), along with ERβ1, is significantly expressed in TNBC and stimulates high ERβ mRNA in TNBC cells. This work may help elucidate the interplay of metabolic and growth factors in TNBC.

Identification of cytoplasmic proteins interacting with unliganded estrogen receptor α and β in human breast cancer cells

Estrogen receptor subtypes (ERα and ERβ) are transcription factors sharing a similar structure but exerting opposite roles in breast cancer cells. Besides the well-characterized genomic actions of nuclear ERs upon ligand binding, specific actions of ligand-free ERs in the cytoplasm also affect cellular functions. The identification of cytoplasmic interaction partners of unliganded ERα and ERβ may help characterize the molecular basis of the extra-nuclear mechanism of action of these receptors, revealing novel mechanisms to explain their role in breast cancer response or resistance to endocrine therapy. To this aim, cytoplasmic extracts from human breast cancer MCF-7 cells stably expressing tandem affinity purification-tagged ERα and ERβ and maintained in estrogen-free medium were subject to affinity-purification and MS analysis, leading to the identification of 84 and 142 proteins associated with unliganded ERα and ERβ, respectively. Functional analyses of ER subtype-specific interactomes revealed significant differences in the molecular pathways targeted by each receptor in the cytoplasm. This work, reporting the first identification of the unliganded ERα and ERβ cytoplasmic interactomes in breast cancer cells, provides novel experimental evidence on the nongenomic effects of ERs in the absence of hormonal stimulus. All MS data have been deposited in the ProteomeXchange with identifier PXD001202 (http://proteomecentral.proteomexchange.org/dataset/PXD001202).