Expression of estrogen receptor β wt isoform (ERβ1) and ERβΔ5 splice variant mRNAs in sporadic breast cancer

Additional confirmation of successful cell suspension fractionation of metastatic axillary node tissue

We present herein an extension to our recently developed and published method termed "Fractionation of Nodal Cell Suspension" (FNCS). The method enables efficient subcellular fractionation into nuclear (N) and cytosolic (C) compartments of extremely fibrous and problematic metastatic axillary lymph node (mALN) tissue, using the entire nodule. For the purpose of the present study, a case of invasive lobular breast cancer (BC) patient with pT2N3aMx status and defined primary tumor markers (ERα 8, PR-B 8, and HER2 score 0) was available. Initially, the mALN tissue of this patient was analyzed by immunohistochemistry (IHC), and a positive correlation of nodal ERα, PR-B and HER2 biomarkers to those of the primary tumor was obtained. Subsequently, the mALN was FNCS fractionated into N and C, and Western blot (WB) analysis demonstrated a single band for ERα, PR-B and nuclear loading control (HDAC1) in nuclear, but not in the cytosolic compartments, confirming the efficiency of our fractionation protocol. At the same time, HER2 bands were not observed in either compartment, in accordance with HER2 negativity determined by IHC in both primary tumor and mALN tissue. In conclusion, by confirming the nuclear expression of ERα and PR-B biomarkers in metastatic loci, we demonstrate the purity of the FNCS-generated compartments - the protocol that offers a reliable tool for further analysis of nuclear versus cytosolic content in downstream analysis of novel biomarkers in the whole mALN of BC patients.

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.

The RNA Splicing Response to DNA Damage

The number of factors known to participate in the DNA damage response (DDR) has expanded considerably in recent years to include splicing and alternative splicing factors. While the binding of splicing proteins and ribonucleoprotein complexes to nascent transcripts prevents genomic instability by deterring the formation of RNA/DNA duplexes, splicing factors are also recruited to, or removed from, sites of DNA damage. The first steps of the DDR promote the post-translational modification of splicing factors to affect their localization and activity, while more downstream DDR events alter their expression. Although descriptions of molecular mechanisms remain limited, an emerging trend is that DNA damage disrupts the coupling of constitutive and alternative splicing with the transcription of genes involved in DNA repair, cell-cycle control and apoptosis. A better understanding of how changes in splice site selection are integrated into the DDR may provide new avenues to combat cancer and delay aging.

Triple-negative breast cancer: investigating potential molecular therapeutic target

INTRODUCTION

Triple-negative breast cancer (TNBC) makes up about 10 - 20% of all breast cancers and the lack of hormone receptors and human epidermal growth factor receptor-2/Neu expression is responsible for poor prognosis, no targeted therapies and trouble in the clinical management. Tumor heterogeneity, also within the same tumor, is a major cause for this difficulty. Based on the introduction of new biological drugs against different kinds of tumor, many efforts have been made for classification of genetic alterations present in TNBC, leading to the identification of several oncogenes and tumor suppressor genes involved in breast cancer carcinogenesis.

AREAS COVERED

In this review we investigated the molecular alteration present in TNBC which could lead to the creation of new targeted therapies in the future, with the aim to counteract this disease in the most effective way.

EXPERT OPINION

In this context some hormone receptors like G-protein-coupled receptor 30 and androgen receptors may be a fascinating area to investigate; also, angiogenesis, represented not only by the classical VEGF/VEGFR relationship, but also by other molecules, like semaphorins, fibroblast growth factor and heparin-binding-EGF-like, is a mechanism in which new developments are expected. In this perspective, one technique that may show promise is the gene therapy; in particular the gene transfer could correct abnormal genetic function in cancer cells.

Estrogen receptors and human disease: an update

A myriad of physiological processes in mammals are influenced by estrogens and the estrogen receptors (ERs), ERα and ERβ. As we reviewed previously, given the widespread role for estrogen in normal human physiology, it is not surprising that estrogen is implicated in the development or progression of a number of diseases. In this review, we are giving a 5-year update of the literature regarding the influence of estrogens on a number of human cancers (breast, ovarian, colorectal, prostate, and endometrial), endometriosis, fibroids, and cardiovascular disease. A large number of sophisticated experimental studies have provided insights into human disease, but for this review, the literature citations were limited to articles published after our previous review (Deroo and Korach in J Clin Invest 116(3):561-570, 2006) and will focus in most cases on human data and clinical trials. We will describe the influence in which estrogen's action, through one of or both of the ERs, mediates the aforementioned human disease states.

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.

Polymorphisms of estrogen receptors: risk factors for invasive melanoma - a prospective study

Cross-sectional studies have reported associations between a number of polymorphisms in the estrogen receptor alpha (ERα) gene and the body mass index, hypertension, coronary flow reserve, coronary atherosclerosis, and osteoporosis. There are currently no data examining the genetic polymorphisms of the ERα and estrogen receptor beta (ERβ) genes in melanoma patients. The aims of this study were to investigate the associations of genetic polymorphisms of the ERα and ERβ genes with melanoma risk. The study group consisted of consecutive patients who visited the Department of Dermatology of the University of Florence between March 2005 and July 2007 for surgical excision of melanoma. In our study, homozygosity for the wild-type alleles showed different results at the PvuII, XbaI, and AluI restriction sites. Only the AluI site showed a lower proportion of the A allele in the melanoma group compared to the control group; the P and X alleles were lower in the control group than in the melanoma group. The distribution of wild-type alleles is important because these alleles have a protective role in the expression of altered proteins, which involves the ERs in our case. Because of the phenotypic prevalence of the wild-type allele, the heterozygotes did not express the polymorphism. The homozygosity of the polymorphic-type alleles shows that a alleles are more frequent in the case group than in the control group, with proportions of 43.8 and 39.5%, respectively. These results suggest that a polymorphism at the AluIrestriction site correlates with a higher proportion of melanoma. Thus, the polymorphism of ERβ could ascribe to a higher susceptibility to melanoma.

Levels of estrogen receptor B splice variant (ERBΔ5) mRNA correlates with progesterone receptor in breast carcinomas

It is well known that breast tumors which are estrogen positive ER(+) are more likely to respond to hormone therapy. However, a certain percentage of ER(+)/PR(+) tumors do not respond to this therapy. Identification of the second estrogen receptor, named estrogen receptor beta (ER?), as well as the existence of numerous isoforms/splice variants of both ER? and ER?, suggests that a complex regulation of estrogen action exists. In this study, we analyzed the expression ratio of ER?1 isoform and ER??5 splice variant mRNAs, and its correlation with ER/PR status by quantitative RT-PCR and clinical and histopathological parameters. We found that the relative proportion of ER??5 in the total ER?1 transcript 'pool' inversely correlates with the PR level (p = -0,359, p< 0,003, Spearman). It may be that the ER??5 variant modulates the ER? activity of downstream targets. In addition, we suggest that the determination of the expression profiles of ER? and ER? isoforms and splice variants in the defined groups of patients are necessary for elucidating their involvement in endocrine resistance.

Highly concordant coexpression of aromatase and estrogen receptor beta in non-small cell lung cancer

Estrogen receptor expression has been reported in non-small cell lung cancer. We examined the correlation between aromatase, a key enzyme in the synthesis of estrogen, and estrogen receptor expressions in 105 non-small cell lung cancer cases. All patients were older than 60 years, and all female patients were postmenopausal. Estrogen receptor alpha and progesterone receptor were detected in only 1 and 14 cases, respectively. Estrogen receptor beta and aromatase were positive in 75 and 89 cases respectively. Estrogen receptor beta expression in non-small cell lung cancer showed an inverse correlation with lymph node metastasis (P < .05). Only among females, both estrogen receptor beta and aromatase expressions were correlated with higher Ki-67 labeling index and younger age (P < .05). Among 89 aromatase-positive cases, 70 were positive for estrogen receptor beta, demonstrating a significant concordance (P < .05). Simultaneous immunohistochemical staining for aromatase and estrogen receptor beta showed a high rate of double positive association. Male non-small cell lung cancer cases with double positivity for aromatase and estrogen receptor beta demonstrated lower status in N factor by TNM classification (P < .05). In addition, among 89 aromatase-positive cases, a low-Allred total score of estrogen receptor beta showed a significant relationship with large tumor size and high T factor by TNM classification (P < .05). In conclusion, frequent coexpression of aromatase and estrogen receptor beta in non-small cell lung cancer might suggest some functional correlation between aromatase and estrogen receptor beta, whereas estrogen receptor beta negativity might be correlated with malignant progression of non-small cell lung cancer.

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.

ERalpha-negative and triple negative breast cancer: molecular features and potential therapeutic approaches

Triple negative breast cancer (TNBC) is a type of aggressive breast cancer lacking the expression of estrogen receptors (ER), progesterone receptors (PR) and human epidermal growth factor receptor-2 (HER-2). TNBC patients account for approximately 15% of total breast cancer patients and are more prevalent among young African, African-American and Latino women patients. The currently available ER-targeted and Her-2-based therapies are not effective for treating TNBC. Recent studies have revealed a number of novel features of TNBC. In the present work, we comprehensively addressed these features and discussed potential therapeutic approaches based on these features for TNBC, with particular focus on: 1) the pathological features of TNBC/basal-like breast cancer; 2) E(2)/ERbeta-mediated signaling pathways; 3) G-protein coupling receptor-30/epithelial growth factor receptor (GPCR-30/EGFR) signaling pathway; 4) interactions of ERbeta with breast cancer 1/2 (BRCA1/2); 5) chemokine CXCL8 and related chemokines; 6) altered microRNA signatures and suppression of ERalpha expression/ERalpha-signaling by micro-RNAs; 7) altered expression of several pro-oncongenic and tumor suppressor proteins; and 8) genotoxic effects caused by oxidative estrogen metabolites. Gaining better insights into these molecular pathways in TNBC may lead to identification of novel biomarkers and targets for development of diagnostic and therapeutic approaches for prevention and treatment of TNBC.

Correlation of body mass index and menopausal status with the intra-tumoral estrogen system in invasive breast cancer

OBJECTIVE

Obesity increases breast cancer risk in post-menopausal women. This is, in part, due to elevated non-glandular aromatase activity, resulting in higher estradiol serum levels. We tested the hypothesis that obesity and menopausal status influence the intra-tumoral estrogen system of breast cancer tissue.

DESIGN

Breast cancer tissue and fasting serum were collected from 26 female patients. After microdissection of the frozen samples, RNA was isolated, and expression of estrogen receptor (ER)alpha, ERbeta1, ERbeta2, ERbeta5, CYP19 aromatase and steroid sulfatase was measured on mRNA level by means of real time RT-PCR. Fasting estradiol serum levels were analysed by ELISA.

RESULTS

Post-menopausal women older than 70 years exhibited a significantly higher expression both of steroid sulfatase and ERalpha than did pre-menopausal women younger than 50 years. We identified a significant positive correlation between body mass index (BMI) and lymphovascular/vascular invasion. A significant inverse correlation between ERalpha and ERbeta2 expression was identified in invasive breast cancer tissue irrespective of BMI or menopausal status.

CONCLUSION

In conclusion, we report an association between menopausal status - but not BMI - and the intra-tumoral expression of steroid sulfatase and ERalpha. Our observation that BMI was associated with invasiveness supports the hypothesis that metabolic factors are able to affect essential features of breast cancer.

Do Estrogen Receptor beta Polymorphisms Play A Role in the Pharmacogenetics of Estrogen Signaling?

Estrogen hormones play critical roles in the regulation of many tissue functions. The effects of estrogens are primarily mediated by the estrogen receptors (ER) alpha and beta. ERs are ligand-activated transcription factors that regulate a complex array of genomic events that orchestrate cellular growth, differentiation and death. Although many factors contribute to their etiology, estrogens are thought to be the primary agents for the development and/or progression of target tissue malignancies. Many of the current modalities for the treatment of estrogen target tissue malignancies are based on agents with diverse pharmacology that alter or prevent ER functions by acting as estrogen competitors. Although these compounds have been successfully used in clinical settings, the efficacy of treatment shows variability. An increasing body of evidence implicates ERalpha polymorphisms as one of the contributory factors for differential responses to estrogen competitors. This review aims to highlight the recent findings on polymorphisms of the lately identified ERbeta in order to provide a functional perspective with potential pharmacogenomic implications.

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.