Association of oestrogen receptor beta 2 (ER beta 2/ER beta cx) with outcome of adjuvant endocrine treatment for primary breast cancer--a retrospective study

ERβ Isoforms Have Differential Clinical Significance in Breast Cancer Subtypes and Subgroups

ERβ, an ER subtype first identified in 1996, is highly expressed in different types of BCa including ERα-negative BCa and TNBC. Many studies on ERβ expression investigated mostly on ERβ1 protein expression in ERα-positive and ERα-negative BCa combined. The results are conflicting. This may be due to the complexity of ERβ isoforms, subject heterogeneity, and various study designs targeting different ERβ isoforms and either ERβ protein or mRNA expression, as well as to the lack of a standardized testing protocol. Herein, we simultaneously investigated both mRNA and protein expression of ERβ isoforms 1, 2, and 5 in different BCa subtypes and clinical characteristics. Patient samples (138) and breast cancer cell lines (BCC) reflecting different types of BCa were tested for ERα and ERβ mRNA expression using quantitative real-time PCR, as well as for protein expression of ERα, ERβ1, ERβ2, and ERβ5 isoforms, PR, HER2/neu, Ki-67, CK 5/6, and p53 using immunohistochemistry. Associations of ERβ isoform expression with clinical characteristics and overall survival (OS) were analyzed. ERβ1, 2, and 5 isoforms are differentially expressed in different BCa subtypes including ERα-negative and TNBC. Each ERβ isoform seemingly plays a distinct role and is associated with clinical tumor characteristics and patient outcomes. ERβ isoform expression is significantly associated with >15% Ki-67 positivity and poor prognostic markers, and it predicts poorer OS, mostly in the subgroups. High ERβ2 and 5 isoform expression in ERα-negative BCa and TNBC is predictive of poor OS. Further investigation of ERβ isoforms in a larger cohort of BCa subgroups is needed to evaluate the role of ERβ for the potential usefulness of ERβ as a prognostic and predictive marker and for therapeutic use. The inconsistent outcomes of ERβ isoform mRNA or protein expression in many studies suggest that the standardization of ERβ testing would facilitate the use of ERβ in a clinical setting.

Estrogen Receptor β Expression and Its Clinical Implication in Breast Cancers: Favorable or Unfavorable?

There are two estrogen receptor (ER) genes (ESR1/ERα and ESR2/ERβ) in humans. Of those. ERβ, the second ER isotype identified in 1996, is differentially expressed in different phenotypes and molecular subtypes of breast cancer (BCa), and is highly expressed in ERα-negative BCa and triple-negative BCa (TNBC). This review summarizes the potential clinical relevance of ERβ in BCa and the challenges associated with studies on the role of ERβ in BCa. The experimental and clinical studies evaluating clinical outcomes and associations with clinical characteristics and responses to endocrine therapy on targeting ERβ reviewed herein indicate that ERβ is a clinically important biomarker in BCa. The reviewed studies also suggest that each ERβ isoform has a distinct role in BCa subtypes and the potential of novel- targeted therapies in BCa, especially ERα-negative BCa and TNBC. However, the findings of many studies on ERβ are inconsistent, and the exact role of ERβ in BCa remains elusive; this may potentially be attributed to the complexity of ERβ isoforms, but also to the lack of standardized testing protocol. Thus, successful clinical application of ERβ requires the development of standardized, reproducible, and objective measurement methods for ERβ that can be widely and routinely applied in clinical setting.

Estrogen Receptor Beta: The Promising Biomarker and Potential Target in Metastases

The discovery of the Estrogen Receptor Beta (ERβ) in 1996 opened new perspectives in the diagnostics and therapy of different types of cancer. Here, we present a review of the present research knowledge about its role in endocrine-related cancers: breast, prostate, and thyroid, and colorectal cancers. We also discuss the reasons for the controversy of its role in carcinogenesis and why it is still not in use as a biomarker in clinical practice. Given that the diagnostics and therapy would benefit from the introduction of new biomarkers, we suggest ways to overcome the contradictions in elucidating the role of ERβ.

Hormone Receptor Expression on Endocrine Therapy in Patients with Breast Cancer: A Meta-Analysis

OBJECTIVE

To evaluate the role of hormone receptor expression on endocrine therapy in patients with breast cancer.

METHODS

The databases were used to collect the effect of high expression and low expression of hormone receptors on the efficacy of endocrine therapy in breast cancer. Two evaluators independently screened the literature based on preset inclusion and exclusion criteria. The quality of the article was evaluated using a modified Newcastle-Ottawa Scale (NOS) system. The survival data included in the literature were extracted and the ln(hazard ratio (HR)) and se[ln(HR)] of the overall survival (OS), disease-free survival (DFS), and recurrence-free survival (RFS) rates were calculated according to different level of hormone receptors. The RevMan 5.3 software was used to evaluate the meta-analysis.

RESULTS

A total of 13 relevant literature were included in the study. There were 8318 estrogen receptor (ER)-positive and 7926 progesterone receptor (PR)-positive patients. Overall survival, DFS, and RFS rates in high expression of ER(+) patients were significantly higher in low expression of ER(+) patients (OS HR = .59, 95% confidence interval (CI): .46-.76, P < .0001; DFS HR = .62, 95%CI: .50-.76, P < .00001; RFS HR = .44, 95% CI: .33-.58, P < .00001). In patients with high expression of PR(+), OS, DFS, and RFS rates were significantly higher than those with low expression of PR(+) (OS HR = .66, 95% CI: .57-.78, P < .00001; DFS HR = .52, 95% CI: .42-.65, P < .00001; RFS HR = .24, 95% CI: .11-.53, P = .0004).

CONCLUSION

The expression of ER and PR are powerful predictors of adjuvant endocrine therapy response. Breast cancer patients with high expression of hormone receptors benefit more from endocrine therapy and have better prognosis.

Oestrogen receptor β (ERβ) regulates osteogenic differentiation of human dental pulp cells

Estradiol (E₂) has many important actions in the tissues of the oral cavity. Disruption of E₂ metabolism or alterations in systemic E₂ concentrations have been associated with compromised periodontal health. In many instances such changes occur secondarily to the well characterised effects of E₂ on bone physiology -especially maintenance of bone mineral density (BMD). Despite these important epidemiological findings, little is known about the mechanism of action of E₂ in oral tissues or the expression and function of oestrogen receptor (ER) isoforms in these tissues. We have isolated human dental pulp cells (hDPCs), which are able to differentiate towards an osteogenic lineage under appropriate culture conditions. We show that hDPCs express ERα, ERβ1, ERβ2 and the cell membrane associated G protein-coupled ER (GPR30). Following osteogenic differentiation of hDPCs, ERβ1 and ERβ2 were up regulated approximately 50-fold while ERα and GPR30 were down regulated, but to a much lesser degree (approximately 2-fold). ERβ was characterised as a 59kDa protein following Western blot analysis with validated antibodies and ERβ was detected in both nuclear and cytoplasmic cell compartments following immunofluorescence (IF) and immunohistochemical (IHC) analysis of cultured cells. Furthermore isoform specific antibodies detected both ERβ1 and ERβ2 in DPC cultures and in situ analysis of ERβ expression in decalcified tooth/pulp sections identified the odontoblast layer of pulp cells juxtaposed to the tooth enamel as strongly reactive for both ERβ isoforms. Finally the use of isoform specific agonists identified ERβ as the main receptor responsible for the pro-osteogenic effect of oestrogenic hormones in this tissue. Our data suggest that oestrogens stimulated osteogenic differentiation in hDPCs and that this action is mediated principally through the ERβ isoform. These findings may have important consequences for the investigation and treatment of oral and periodontal pathologies which are associated with imbalances in oestrogen concentrations and action.

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.

Altered expression of estrogen receptor β2 is associated with different biological markers and clinicopathological factors in papillary thyroid cancer

Estrogen and estrogen receptor (ER)-α and -β play a role in the development and progression of thyroid cancer. ERβ2 is one major splicing variant of ERβ. In this study, we investigated the clinical significance of ERβ2 protein expression in the papillary thyroid carcinoma (PTC) lesion. ERβ2 expression was immunohisto-chemically examined in formalin-fixed, paraffin-embedded thyroid tissues from 106 patients with PTC by Elivision™ plus two-step system as previously described. The relationships between ERβ2 expression and clinicopathological/biological factors were then analyzed. ERβ2 protein was expressed in all the PTC patients studied. It was positively associated with Ki-67 expression in female PTC patients with advanced reproductive age (>45 years, in low-estrogen status) and with VEGF expression in male PTC patients with reproductive age (18~45 years, in low-estrogen status) (P=0.005 and P=0.044, respectively). There was no association between ERβ2 expression and tumor size, extrathyroidal extension and tumor-node-metastasis stage in PTC patients. In addition, ERβ2 expression was lower in female patients of reproductive age (18~45 years, in relatively high-estrogen status) with lymph node metastasis than that in those patients without lymph node metastasis (P=0.035). The present results suggest that the expression of ERβ2 in PTC is associated with the progression of the disease. Its potential effect may vary with different estrogen status. Further study will assess the underlying molecular mechanisms of ERβ2 in PTC.

Expression and prognostic value of estrogen receptor β in patients with triple-negative and triple-positive breast cancer

The aim of the present study was to investigate the expression of estrogen receptor β (ERβ) in triple-negative and triple-positive breast cancer patients, and evaluate its utility as a prognostic factor. Between January 2000 and December 2010, primary tumor tissue samples were collected from 234 subjects, including 107 triple-negative and 127 triple-positive breast cancer patients. The samples were embedded in paraffin and immunohistochemical staining was conducted to determine the expression levels of ERβ. The Kaplan-Meier method was used to analyze patient survival rates. ERβ expression was observed in 38/107 patients (35.5%) with triple-negative breast cancer and 63/127 patients (49.6%) with triple-positive breast cancer. The ERβ expression rate was significantly decreased in the patients with triple-negative breast cancer, as compared with those with triple-positive breast cancer (P=0.03). Analysis of the survival rates indicated that patients with triple-negative breast cancer and positive ERβ expression exhibited poor disease progression-free survival (DFS) compared with those with negative ERβ expression (P=0.021). However, no statistically significant difference was observed in the DFS between the triple-positive breast cancer patients with positive and negative ERβ expression. Therefore, the expression of ERβ varies between triple-negative and triple-positive breast cancer patients. In addition, positive expression of ERβ indicates a poor prognosis in triple-negative breast cancer patients; however, this is not the case for triple-positive breast cancer patients.

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.

Lobular breast cancers lack the inverse relationship between ER/PR status and cell growth rate characteristic of ductal cancers in two independent patient cohorts: implications for tumor biology and adjuvant therapy

BACKGROUND

Although invasive lobular carcinoma (ILC) of the breast differs from invasive ductal carcinoma (IDC) in numerous respects - including its genetics, clinical phenotype, metastatic pattern, and chemosensitivity - most experts continue to manage ILC and IDC identically in the adjuvant setting. Here we address this discrepancy by comparing early-stage ILC and IDC in two breast cancer patient cohorts of differing nationality and ethnicity.

METHODS

The clinicopathologic features of 2029 consecutive breast cancer patients diagnosed in Hong Kong (HK) and Australia (AUS) were compared. Interrelationships between tumor histology and other clinicopathologic variables, including ER/PR and Ki67, were analysed.

RESULTS

Two hundred thirty-nine patients were identified with ILC (11.8%) and 1790 patients with IDC. AUS patients were older (p <0.001) and more often postmenopausal (p <0.03) than HK patients. As expected, ILC tumors were lower in grade and proliferative rate, and more often ER-positive and HER2-negative, than IDC (p <0.002); yet despite this, ILC tumors were as likely as IDC to present with nodal metastases (p >0.7). Moreover, whereas IDC tumors exhibited a strongly negative relationship between ER/PR and Ki67 status (p <0.0005), ILC tumors failed to demonstrate any such inverse relationship (p >0.6).

CONCLUSION

These data imply that the primary adhesion defect in ILC underlies a secondary stromal-epithelial disconnect between hormonal signaling and tumor growth, suggesting in turn that this peritumoral feedback defect could reduce both the antimetastatic (adjuvant) and tumorilytic (palliative) efficacy of cytotoxic therapies for such tumors. Hence, we caution against assuming similar adjuvant chemotherapeutic survival benefits for ILC and IDC tumors with similar ER and Ki67, whether based on immunohistochemical or gene expression assays.

Expression and prognostic value of estrogen receptor beta in breast cancer patients

This study is to determine the expression of estrogen receptor beta (ERβ) in breast cancer patients and to evaluate its relationship with clinicopathological parameters of breast cancer and its effects on the prognosis of breast cancer patients. Paraffin-embedded primary tumor tissue sections from 490 breast cancer patients were collected consecutively from January 2000 to December 2010. They had complete clinical data and follow-up records. Immunohistochemical staining was conducted to determine ERβ expression. The Kaplan-Meier method was used for survival analysis. Difference in survival was analyzed by the Log-Rank test. The Cox proportional hazard model was performed to evaluate the prognostic value of ERβ expression in breast cancer patients. The ERβ high and over expression rate in 490 breast patients was 22.4% (110/490). ERβ expression was not associated with clinicopathological parameters of breast cancer. The mean survival time in patients with ERβ negative expression, ERβ low expression, ERβ high expression and ERβ over expression was 9.9 years, 9.2 years, 8.6 years and 5.6 years. Statistically, patients with ERβ high and over expression had significantly shorter disease-free survival (DFS) time compared with the patients with ERβ negative and low expression. The Cox multivariate analysis revealed that ERβ high and over expression, the pathologic stages of tumor and chemotherapy were the independent predictors for poor DFS in breast cancer patients. ERβ expression is an independent prognostic factor of breast cancer patients and its high and over expression indicates poor prognosis of breast cancer. There was no correlation between ERβ expression and clinicopathological parameters in breast cancer.

Estrogen receptor beta in breast cancer

Estrogen is essential for growth and development of the mammary glands and has been associated with the promotion and growth of breast cancer and in line with this, most human breast cancers are initially estrogen-dependent and undergo regression when deprived of their supporting hormone. Estrogen exerts many of its effects via two nuclear estrogen receptors (ERs), ERα and ERβ. The discovery of a second ER, ERβ, demanded a full re-evaluation of estrogen action in all target tissues and different estrogen associated diseases, including human breast cancer. However, despite over 15 years of research, the exact role, if any, of ERβ in human breast cancer remains elusive. The main challenges now are to develop highly selective anti-ERβ antibodies that are applied to large well characterized human breast cancer samples to validate their diagnostic potential and to explore ERβ-selective agonists in animal models of breast cancer to validate their therapeutic potential.

Insight into the mechanisms of action of estrogen receptor β in the breast, prostate, colon, and CNS

Estrogen and its receptors (ERs) influence many biological processes in physiology and pathology in men and women. ERs are involved in the etiology and/or progression of cancers of the prostate, breast, uterus, ovary, colon, lung, stomach, and malignancies of the immune system. In estrogen-sensitive malignancies, ERβ usually is a tumor suppressor and ERα is an oncogene. ERβ regulates genes in several key pathways including tumor suppression (p53, PTEN); metabolism (PI3K); survival (Akt); proliferation pathways (p45(Skp2), cMyc, and cyclin E); cell-cycle arresting factors (p21(WAF1), cyclin-dependent kinase inhibitor 1 (CDKN1A)), p27(Kip1), and cyclin-dependent kinases (CDKs); protection from reactive oxygen species, glutathione peroxidase. Because they are activated by small molecules, ERs are excellent targets for pharmaceuticals. ERα antagonists have been used for many years in the treatment of breast cancer and more recently pharmaceutical companies have produced agonists which are very selective for ERα or ERβ. ERβ agonists are being considered for preventing progression of cancer, treatment of anxiety and depression, as anti-inflammatory agents and as agents, which prevent or reduce the severity of neurodegenerative diseases.

Potential clinical significance of ERβ ON promoter methylation in sporadic breast cancer

The aim of the study was to assess how hypermethylation of the ON promoter of the estrogen receptor beta (ERβ) gene affects its expression (at the mRNA and protein level) and to correlate these with some clinical and histopathological parameters. A total of 131 samples of frozen breast cancer tissue was analyzed. A custom-designed, two-step PCR method was used to measure the methylation index of the ERβ gene ON promoter region. Quantitative reverse transcriptase-polymerase chain reaction (qRT-PCR) was performed to quantify mRNA of the ERβ1 isoform, while ERβ1 protein was determined using the Western blot method. There was a significant difference in the methylation index of the ERβ gene ON promoter between the groups of patients with negative and positive axillary lymph node status (P = 0.03). In addition, the methylation index of the ON promoter was positively correlated with estrogen receptor alfa (ERα) protein levels (ρ = 0.31, P = 0.02). There was a significant difference in the methylation index of the ON promoter between the progesterone receptor (PR)-negative and PR-positive groups of patients (P = 0.01). ERβ1 protein levels were negatively correlated with ERα protein (ρ = -0.27, P < 0.01). The methylation index of the ON promoter could be a more reliable additional parameter for prediction and/or prognosis in breast cancer than ERβ1-mRNA and/or protein levels.

Significance of rs1271572 in the estrogen receptor beta gene promoter and its correlation with breast cancer in a southwestern Chinese population

Background

To characterize single nucleotide polymorphisms (SNPs) within the promoter region of the estrogen receptor beta (ERβ) gene and to analyze the association of ERβ SNPs with susceptibility to breast cancer. Genotype frequencies of five SNPs (rs3020449, rs3020450, rs2987983, rs1271572 and rs1887994) in the promoter region of the ERβ gene in 873 women with breast cancer, 645 women with fibroadenoma and 700 healthy women were determined using an allele-specific tetra-primer polymerase chain reaction (PCR). Kaplan-Meier survival analysis was performed to evaluate the association of selected rs1271572 with prognosis in breast cancer. Electrophoretic mobility-shift assays were conducted to explore the binding of SNP rs1271572 containing probes to transcriptional factor Ying Yang 1 (YY1).

Results

Women with the homozygous TT genotype of rs1271572 had a significantly higher risk in developing breast cancer. Breast cancer patients with the TT genotype of rs1271572 had lower five-year survival rates than those with other genotypes and were more likely to suffer brain metastases. The rs1271572 G→T SNP abrogated YY1 binding and reduced the transcription activity of the promoter 0 N in the ERβ gene in vitro.

Conclusions

TT genotype of rs1271572 is associated with increased risk for breast cancer in Chinese women and is associated with unfavored prognosis in Chinese breast cancer patients. TT genotype of rs1271572 inhibited expression of ERβ gene by down regulating transcriptional activity of the promoter 0 N in the ERβ gene. Our data revealed that the TT genotype of rs1271572 resulted in loss of the YY1 binding site and reduced the transcription activity of the promoter 0 N in the ERβ gene.

Taxa de sobrevida na mulher com câncer de mama: estudo de revisão

Revisão integrativa que identificou nas publicações da LILACS, SciELO e PubMed, período 2004-2009, fatores contribuintes para a elevação das taxas de sobrevida em cinco anos e sobrevida livre de doenças em cinco anos das mulheres com câncer de mama. Os resultados, 40 publicações, demonstraram maior incidência da doença nas idades 50-60 e 40-49 anos. Programas de rastreamento, elevação da escolaridade, do padrão socioeconômico, métodos diagnósticos genéticos, imuno-histoquímicos e citológicos, associação das novas terapêuticas com as convencionais são fatores contribuintes para elevação das taxas de sobrevidas, da qualidade de vida e do cuidado à mulher com câncer de mama.

Evaluation of ER-α, ER-Β1 and ER-Β2 expression and correlation with clinicopathologic factors in invasive luminal subtype breast cancers

PURPOSE

Luminal subtype breast cancer is defined as oestrogen receptor (ER)- and/or progesterone receptor (PR)- positive breast cancer. We detected the expression of ER-α, ER-Β1 and ER-Β2 in the tissue samples of invasive luminal subtype breast cancer patients, evaluated the correlations between these ER statuses and prognosis, and tried to clarify whether the status of ER-α isoforms provides clinically useful information further to what is already provided by the traditional ER-α/PR assay.

METHODS

The expression of ER-α, ER-Β1 and ER-Β2 in the paraffin-embedded sections of 162 invasive luminal subtype breast cancer patients was detected with an immunohistochemical staining method. With mid-long-term follow-up, the features of ER-α, ER-Β1 and ER-Β2 status and the correlations between clinical characteristics and the prognosis were analysed.

RESULTS

ER-Β1-positive status was correlated with PR (rs=0.217, p<0.01). The median follow-up time was 92 months (range, 4-98 months). Univariate analysis suggested that ER-Β1 status was significantly correlated to diseasefree survival (DFS) time (log rank=3.98, p=0.046), especially in patients with positive lymph nodes (log rank=6.20, p=0.013). In patients with smaller tumour size (=20 mm), negative ER-Β2 status was significantly correlated to overall survival time (log rank=3.87, p=0.049).

CONCLUSIONS

In invasive luminal subtype breast cancers, ER-Β1 is correlated with good prognosis and could be regarded as one of the factors for evaluating DFS time, especially in lymph node-positive patients. There may be some interactions between ER-Β1 and PR. In clinical practice, besides routine detection of ER-α and PR in invasive luminal subtype breast cancers, immunohistochemical staining of ER-Β1 and ER-Β2 should be considered in order to achieve more useful information. Further studies are needed to confirm our findings.

Estrogen receptor-beta and breast cancer: translating biology into clinical practice

Estrogen receptor (ER) β was discovered over a decade ago. The design of most studies on this receptor was based on knowledge of its predecessor, ERα. Although breast cancer (BCa) has been a main focus of ERβ research, its precise roles in breast carcinogenesis remain elusive. Data from in vitro models have not always matched those from observational or clinical studies. Several inherent factors may contribute to these discrepancies: (a) several ERβ spliced variants are expressed at the protein level, and isoform-specific antibodies are unavailable for some variants; (b) post-translational modifications of the receptor regulate receptor functions; (c) the role of the receptor differs significantly depending on the type of ligands, cis-elements, and co-regulators that interact with the receptor; and (d) the diversity of distribution of the receptor among intracellular organelles of BCa cells. This review addresses the gaps in knowledge in ERβ research as it pertains to BCa regarding the following questions: (1) is ERβ a tumor suppressor in BCa?; (2) do ERβ isoforms play differential roles in breast carcinogenesis?; (3) do nuclear signaling and extranuclear ERβ signaling differ in BCa?; (4) what are the consequences of post-translational modifications of ERβ in BCa?; (5) how do co-regulators and interacting proteins increase functional diversity of ERβ?; and (6) how do the types of ligand and regulatory cis-elements affect the action of ERβ in BCa?. Insights gained from these key questions in ERβ research should help in prevention, diagnosis/prognosis, and treatment of BCa.

Different associations of estrogen receptor β isoforms, ERβ1 and ERβ2, expression levels with tumor size and survival in early- and late-onset breast cancer

BACKGROUND

In breast cancer, little is known about the consequences of co-expression of ERα with the second estrogen receptor, ERβ, and its isoforms in light of their joint prognostic value. Previously reported correlations have been based mostly on independent ERα and ERβ expression levels in breast tumors.

PURPOSE

To address whether the expression ratio of ERα and ERβ and its isoforms may be a more important parameter than their absolute levels, we analyzed relative mRNA expression ratios of ERβ1 to ERβ2 and ERα in 74 clinical samples of invasive breast cancer including 39 early-onset and 35 late-onset breast cancers. Expression levels were correlated with clinical and histopathological parameters and disease-free interval.

RESULTS

A specific correlation of ERβ1 expression levels with tumor size was detected in early-onset breast cancer patients and of ERβ2 levels with tumor size in late-onset patients. Expression of both ERβ isoforms inversely correlated with expression of the two estrogen regulated genes, progesterone receptor and pS2 in both groups. Higher levels of ERβ2 than ERβ1 isoform were associated with a better outcome in late-onset patients.

CONCLUSIONS

Our results suggest that different isoforms of ERβ may be involved in suppression of tumor growth in young and elder patients and may have different prognostic values.

Comparative evaluation of ERα and ERβ significance in breast cancer: state of the art

Over 30 years of clinical data have unequivocally established estrogen receptor (ER)-α as a critical clinical biomarker and valid therapeutic target to fight breast cancer. However, ERα remains imperfect with respect to both of these activities, mainly because the mechanisms by which estrogens mediate their activity are far more complex than originally anticipated. The cloning of a second estrogen receptor, ERβ, has led to a full re-evaluation of our original view of the action of estrogen in breast tissues. Important challenges remain with respect to the design, selection and normalization of the most appropriate methods for assaying the expression and functionality of both receptors. Solving these challenges remains a priority in order to decide upon specific endocrine therapies and save patients who are still dying from a potentially curable disease.

Differential expression pattern of estrogen receptors, aromatase, and sulfotransferase in breast cancer tissue and corresponding lymph node metastases

Patients with hormone receptor positive breast cancer who are treated with endocrine therapy generally have a good prognosis. However, resistance to hormonal therapy and progression occurs, and the reasons for this are manifold. It has been proposed that the local estrogenic environment has a role in the process of local invasion and progression. We have determined the expression pattern of estrogen receptor α, estrogen receptor β, and the epithelial and stromal expression of the estrogen-metabolizing enzymes aromatase and sulfotransferase by immunohistochemistry in tissue arrays, containing 50 paraffin-embedded sets of tissues obtained from breast cancer and from corresponding metastatic axillary lymph nodes of the same patients. We have found statistically significant higher estrogen receptors α and β expression in primary tumors than in corresponding lymph node metastases (p = 0.0004 and p = 0.003, respectively). Aromatase was also expressed more frequently in epithelial as well as in stromal cells of the malignant tumor when compared to according lymph node metastases (p = 0.08 and p = 0.12, respectively). While in lymph node metastases only estrogen receptor α and stromal aromatase expression were correlated (p = 0.01), significant associations were seen between the estrogen receptor β and sromal aromatase, and epithelial sulfotransferase (p = 0.0006 and p = 0.03, respectively) in the primary tumor. We hypothesize that the decreased expression of local estrogens by aromatase, in combination with a decreased expression of estrogen receptors α and β in lymphatic metastases, renders these metastases hormone insensitive and could contribute to the poor response to endocrine therapy that is often seen in nodal-positive tumors.

Divergent mechanisms for trophic actions of estrogens in the brain and peripheral tissues

17β-estradiol (E(2)) can enhance reproductive, cognitive, and affective functions; however, the mechanisms by which E(2) has these effects need to be better understood. Pleiotrophic effects of E(2) can occur via traditional and novel actions at various forms of estrogen receptors (ERs). In the central nervous system, trophic effects of E(2) may be related to beneficial effects of hormone replacement therapy (HRT). However, in peripheral reproductive tissues, E(2)'s capacity to evoke growth can increase risk of cancers. This review focuses on investigations aimed at elucidating divergent mechanisms of steroids to promote trophic effects in the brain, independent of effects on peripheral reproductive tissues. First, actions of estrogens via ERα or ERβ for peripheral growth (carcinogen-induced tumors, uterine growth) and hippocampus-dependent behaviors (affect, cognition) are described. Second, factors that influence these effects of estrogens are described (e.g. experience, timing/critical windows, non-ER mechanisms). Third, effects of estrogens at ERβ related to actions of progestogens, such as 5α-pregnan-3α-ol-20-one (3α,5α-THP) are described. In summary, effects of E(2) may occur via multiple mechanisms, which may underlie favorable effects in the brain with minimal peripheral trophic effects.

Expression of oestrogen receptor beta isoforms is regulated by transcriptional and post-transcriptional mechanisms

Although ERs (oestrogen receptors) mediate breast tumour behaviour, the precise role of ERbeta remains unclear. This is mainly because analyses have been complicated by the presence in breast tissue of three ERbeta protein variants (ERbeta1, ERbeta2 and ERbeta5) that derive from differential 3' splicing. We have recently identified the first known mechanisms responsible for the differential control of isoform expression, involving regulation of translation via 5'-UTRs (untranslated regions). In the present study, we have uncovered further complexity involving the influence of multiple promoters and cross-talk between 5'- and 3'-UTRs. We demonstrate that full-length ERbeta mRNAs are transcribed from three separate promoters; two promoters are well-established within the literature, whereas the third represents a novel finding. Each promoter produces transcripts with distinct 5'-UTRs. The differential 3' splicing that produces transcripts coding for the ERbeta isoforms also defines isoform-specific 3'-UTRs. We identified exact 3'-UTR sequences for each isoform, and have shown that alternative polyadenylation sites are used in a cell-type specific manner to produce transcripts with 3'-UTRs of different lengths. Critically, we show that 5'- and 3'-UTRs combine to specify the efficiencies with which individual transcripts are translated, with 3'-UTR length having a key influence. In addition, we demonstrate how 17beta-oestradiol, a key driver of breast cancer development, affects the regulation of ERbeta expression at both transcriptional and translational levels.

Differential regulation of oestrogen receptor β isoforms by 5' untranslated regions in cancer

Oestrogen receptors (ERs) are critical regulators of the behaviour of many cancers. Despite this, the roles and regulation of one of the two known ERs – ERβ– are poorly understood. This is partly because analyses have been confused by discrepancies between ERβ expression at mRNA and proteins levels, and because ERβ is expressed as several functionally distinct isoforms. We investigated human ERβ 5′ untranslated regions (UTRs) and their influences on ERβ expression and function. We demonstrate that two alternative ERβ 5′UTRs have potent and differential influences on expression acting at the level of translation. We show that their influences are modulated by cellular context and in carcinogenesis, and demonstrate the contributions of both upstream open reading frames and RNA secondary structure. These regulatory mechanisms offer explanations for the non-concordance of ERβ mRNA and protein. Importantly, we also demonstrate that 5′UTRs allow the first reported mechanisms for differential regulation of the expression of the ERβ isoforms 1, 2 and 5, and thereby have critical influences on ERβ function.

Oestrogen receptor splice variants in the pathogenesis of disease

The full-length oestrogen receptor (ER) exists in most vertebrates as two separately encoded isoforms. ER splice variants represent truncated or otherwise modified versions of the full-length alpha or beta isoforms of the parent receptor. ERalpha is found on chromosome 6q and encodes a 595 amino acid protein, while ERbeta is found on chromosome 14q and encodes a 530 amino acid protein. These receptors possess differing ligand affinities, are differentially expressed in a tissue-specific fashion and may act antagonistically. Their altered expression has been implicated in the pathophysiology of a diverse range of conditions from cancer progression in hormone-responsive tissues to neurodegenerative disease. Variously co-expressed with full-length ERs, ER splice variants may have a positive or negative influence on transcription either by modifying the effect of the parent receptor or through their own intrinsic activity. To date, the vast majority of studies have used generic primers or antibodies against the full-length receptors and would not distinguish ER-mediated effects associated with various splice variants. Thus the evidence base of the influence of ER splice variants in normal developmental physiology and in the pathogenesis of disease is weak and greater understanding of their role will undoubtedly lead to new therapeutic strategies for disease intervention and treatment. This review aims to compile the current evidence for the presence of ER splice variants in humans, their physiological roles and clinical sequelae.

Rational management of endocrine resistance in breast cancer: a comprehensive review of estrogen receptor biology, treatment options, and future directions

Endocrine therapy for breast cancer was introduced more than 100 years ago. In the last 30 years, it has been demonstrated that tamoxifen significantly improves outcomes for patients with hormone-responsive breast tumors. Aromatase inhibitors, which suppress the production of estrogen, are recognized today as an effective alternative for estrogen-receptor-positive breast cancer in postmenopausal women. However, despite an initial response to treatment, many tumors eventually recur or progress. When selecting subsequent endocrine therapy, it is helpful to understand the mechanisms of hormone resistance, consider the goals of treatment, and evaluate the clinical potential of each available drug. The objective of this article was to review the underlying mechanisms of action and resistance for each type of hormone therapy, evaluate the most recent data regarding the use of endocrine agents after disease progression or recurrence, and explore potential combinations of hormone therapies with novel molecules that target key growth factor signaling pathways.

A candidate molecular signature associated with tamoxifen failure in primary breast cancer

Introduction

Few markers are available that can predict response to tamoxifen treatment in estrogen receptor (ER)-positive breast cancers. Identification of such markers would be clinically useful. We attempted to identify molecular markers associated with tamoxifen failure in breast cancer.

Methods

Eighteen initially ER-positive patients treated with tamoxifen requiring salvage surgery (tamoxifen failure [TF] patients) were compared with 17 patients who were disease free 5 years after surgery plus tamoxifen adjuvant therapy (control patients). cDNA microarray, real-time quantitative PCR, and immunohistochemistry on tissue microarrays were used to generate and confirm a gene signature associated with tamoxifen failure. An independent series of 33 breast tumor samples from patients who relapsed (n = 14) or did not relapse (n = 19) under tamoxifen treatment from a different geographic location was subsequently used to explore the gene expression signature identified.

Results

Using a screening set of 18 tumor samples (from eight control patients and 10 TF patients), a 47-gene signature discriminating between TF and control samples was identified using cDNA arrays. In addition to ESR1/ERα, the top-ranked genes selected by statistical cross-analyses were MET, FOS, SNCG, IGFBP4, and BCL2, which were subsequently validated in a larger set of tumor samples (from 17 control patients and 18 TF patients). Confirmation at the protein level by tissue microarray immunohistochemistry was observed for ER-α, γ-synuclein, and insulin-like growth factor binding protein 4 proteins in the 35 original samples. In an independent series of breast tumor samples (19 nonrelapsing and 14 relapsing), reduced expression of ESR1/ERα, IGFBP4, SNCG, BCL2, and FOS was observed in the relapsing group and was associated with a shorter overall survival. Low mRNA expression levels of ESR1/ERα, BCL2, and FOS were also associated with a shorter relapse-free survival (RFS). Using a Cox multivariate regression analysis, we identified BCL2 and FOS as independent prognostic markers associated with RFS. Finally, the BCL2/FOS signature was demonstrated to have more accurate prognostic value for RFS than ESR1/ERα alone (likelihood ratio test).

Conclusions

We identified molecular markers including a BCL2/FOS signature associated with tamoxifen failure; these markers may have clinical potential in the management of ER-positive breast cancer.

ERbeta in breast cancer--onlooker, passive player, or active protector?

The role of estrogen exposure in breast cancer risk is well-documented, and both estrogen synthesis and actions through the estrogen receptor (ER) have been targeted by therapies to control hormone-dependent breast cancer. The discovery of a second ER form and its therapeutic implications sparked great interest. Both the original ERalpha and the more recently identified ERbeta subtypes bind and respond similarly to many physiological and pharmacological ligands. However, differences in phytoestrogen binding have been noted, and subtype-specific ligands have been developed. Cell-based assays show that ERbeta and its variants are generally less active on gene transcription than ERalpha, and may influence ERalpha activity; however, both gene- and cell-specific responses occur, and nongenomic activities are less well explored. Specific ligands, and methods to disrupt or eliminate receptor subtype expression in animal and cell models, demonstrate that the ERs have both overlapping and distinct biological functions. Overall, in cell-based studies, ERalpha appears to play a predominant role in cell proliferation, and ERbeta is suggested to be antiproliferative. The potential for distinct populations of breast tumors to be identified based on ER subtype expression, and to exhibit distinct clinical behaviors, is of greatest interest. Several studies suggest that the majority of ER-positive tumors contain both subtypes, but that some tumors contain only ERbeta and may have distinct clinical behaviors and responses. Expression of ERbeta together with ERalpha favors positive responses to endocrine therapy in most studies, and additional studies to determine if the addition of ERbeta to ERalpha as a tumor marker is of clinical benefit are warranted. In contrast, the positive association between ERbeta and HER2 expression in high-grade ERalpha-negative breast cancer does not favor positive responses to endocrine therapy. Expression of ERbeta in specific clinical subpopulations, and the potential for therapies targeting ERbeta specifically, is discussed.

Nuclear and cytoplasmic expression of ERbeta1, ERbeta2, and ERbeta5 identifies distinct prognostic outcome for breast cancer patients

PURPOSE

Previous conflicting results about the prognostic significance of estrogen receptor (ER)-beta in breast cancer may be explained by contribution of isoforms, of which five exist. Our aim was to elucidate the prognostic significance of ERbeta1, ERbeta2, and ERbeta5 by immunohistochemistry in a large cohort of breast carcinomas with long-term follow-up.

EXPERIMENTAL DESIGN

Tissue microarrays were stained with ERbeta1, ERbeta2, and ERbeta5 antibodies and scored as percentage of positive tumor cells and using the Allred system. Nuclear and cytoplasmic staining was evaluated and correlated with histopathologic characteristics, overall survival (OS), and disease-free survival (DFS).

RESULTS

Nuclear ERbeta2 and ERbeta5, but not ERbeta1, significantly correlated with OS (P = 0.006, P = 0.039, and P = 0.099, respectively), and ERbeta2 additionally with DFS (P = 0.013). ERbeta2 also predicted response to endocrine therapy (P = 0.036); correlated positively with ERalpha, progesterone receptor, androgen receptor, and BRCA1; and correlated inversely with metastasis and vascular invasion. Tumors coexpressing ERbeta2 and ERalpha had better OS and DFS. Cytoplasmic ERbeta2 expression, alone or combined with nuclear staining, predicted significantly worse OS. Notably, patients with only cytoplasmic ERbeta2 expression had significantly worse outcome (P = 0.0014).

CONCLUSIONS

This is the first study elucidating the prognostic role of ERbeta1, ERbeta2, and ERbeta5 in a large breast cancer series. ERbeta2 is a powerful prognostic indicator in breast cancer, but nuclear and cytoplasmic expression differentially affect outcome. Measuring these in clinical breast cancer could provide a more comprehensive picture of patient outcome, complementing ERalpha.

Post-transcriptional regulation of gene expression by alternative 5′-untranslated regions in carcinogenesis

Post-transcriptional regulation, via 5′-UTRs (5′-untranslated regions), plays an important role in the control of eukaryotic gene expression. Recent analyses of the mammalian transcriptome suggest that most of the genes express multiple alternative 5′-UTRs and inappropriate expression of these regions has been shown to contribute to the development of carcinogenesis. The present review will focus on the complex post-transcriptional regulation of ERβ (oestrogen receptor β) expression. In particular, results from our laboratory suggest that the expression of alternative 5′-UTRs plays a key role in determining the level of ERβ protein expression. We have also shown that these alternative ERβ 5′-UTRs have a tissue-specific distribution and are differentially expressed between various normal and tumour tissues. Our results also suggest that alternative 5′-UTRs can influence downstream splicing events, thereby perhaps affecting ERβ function. These results suggest that alternative 5′-UTRs may have an overall influence on ER activity and this may have important implications for our understanding of cancer biology and treatment.

The potential role of ER beta isoforms in the clinical management of breast cancer

The discovery of a second oestrogen receptor, ER beta, was a subject of much interest, as this suggested a means to improve the prognostic stratification of invasive breast cancer, better predict response to endocrine therapy, develop new chemotherapeutic/chemopreventative drugs and perhaps prevent inappropriate treatment. However, this has not proved to be straightforward with the discovery of five ER beta isoforms and numerous exon deletion variants. This review sets out to identify the present state of knowledge regarding the clinicopathological role of ER beta isoforms and discusses possible reasons for conflicting results arising from recent research findings.