The potential role of estrogen receptor β2 in breast cancer

Upregulation of collagen type X alpha 1 promotes the progress of triple-negative breast cancer via Wnt/β-catenin signaling

Triple-negative breast cancer (TNBC) is a malignant tumor with high degree of malignancy and lack of effective target treatment. The research aims to explore the role and mechanism of X collagen alpha-1 chain protein (COL10A1 gene) in TNBC. UALCAN and Kaplan-Meier were used to detect the expression of COL10A1 and its role in the prognosis of breast cancer patients. The cells with stably expressing high levels of COL10A1 were obtained by recombinant lentivirus infection. The expression of COL10A1 in cells was temporarily downregulated by siRNA interference fragments. Real-time quantitative polymerase chain reaction and western blot analysis were utilized to detect the changes of COL10A1 mRNA and protein expression. The biological functions of the cells were evaluated by colony formation, cell counting kit-8, cell invasion and wound healing experiments. In addition, the effect of COL10A1 on angiogenesis was investigated by tube formation assay. Xenograft tumor model was used to confirm the effect of COL10A1 on tumorigenicity in vivo and multiplex fluorescent immunohistochemistry to detect multiple proteins simultaneously. The possible molecular mechanism of the function of COL10A1 was speculated through the detection of proteins in functionally related pathways. COL10A1 is highly expressed and is significantly associated with worse overall survival (OS) and recurrence-free survival (RFS) in TNBC. Overexpression of COL10A1 increased the clone formation rate and cell migration capacity of TNBC cells. In the COL10A1 overexpression group, the clone formation rates of MD-MB-231 and BT-549 cells (21.5 ± 0.62, 27.83 ± 3.72)% were significantly higher than those in the control group(15.23 ± 2.79, 19.4 ± 1.47)%, and the relative migration ratio (47.40 ± 3.09, 41.26 ± 4.33)% were higher than those in the control group (34.48 ± 2.03, 21.80 ± 1.03)%. When the expression of COL10A1 was downregulated, the ability of clone formation and wound-healing migration capacity in TNBC cells was weakened. Upregulated COL10A1 in TNBC cells generated more junctions and longer total segments between vascular endothelial cells, and promoted angiogenesis of the cells, and thus enhanced the tumorigenesis. In TNBC, it was found that COL10A1 might affect epithelial-mesenchymal transition (EMT) of the cells through Wnt/β-catenin signaling pathway by the detection of the related pathway proteins. COL10A1 is highly expressed in TNBC, and its high expression leads to poor OS and RFS. COL10A1 may enhance TNBC cell proliferation, migration and tumor-related angiogenesis, and promote tumorigenesis in vivo via Wnt/β-catenin signaling.

Anticancer or carcinogenic? The role of estrogen receptor β in breast cancer progression

Estrogen receptor β (ERβ) is closely related to breast cancer (BC) progression. Traditional concepts regard ERβ as a tumor suppressor. As studies show the carcinogenic effect of ERβ, some people have come to a new conclusion that ERβ serves as a tumor suppressor in estrogen receptor α (ERα)-positive breast cancer, while it is a carcinogen in ERα-negative breast cancer. However, we re-examine the role of ERβ and find this conclusion to be misleading based on the last decade's research. A large number of studies have shown that ERβ plays an anticancer role in both ERα-positive and ERα-negative breast cancers, and its carcinogenicity does not depend solely on the presence of ERα. Herein, we review the anticancer and oncogenic effects of ERβ on breast cancer progression in the past ten years, discuss the mechanism respectively, analyze the main reasons for the inconsistency and update ERβ selective ligand library. We believe a detailed and continuously updated review will help correct the one-sided understanding of ERβ, promoting ERβ-targeted breast cancer therapy.

Dysregulation of splicing variants and spliceosome components in breast cancer

The dysregulation of the splicing process has emerged as a novel hallmark of metabolic and tumor pathologies. In breast cancer (BCa), which represents the most diagnosed cancer type among women worldwide, the generation and/or dysregulation of several oncogenic splicing variants have been described. This is the case of the splicing variants of HER2, ER, BRCA1, or the recently identified by our group, In1-ghrelin and SST5TMD4, which exhibit oncogenic roles, increasing the malignancy, poor prognosis, and resistance to treatment of BCa. This altered expression of oncogenic splicing variants has been closely linked with the dysregulation of the elements belonging to the macromolecular machinery that controls the splicing process (spliceosome components and the associated splicing factors). In this review, we compile the current knowledge demonstrating the altered expression of splicing variants and spliceosomal components in BCa, showing the existence of a growing body of evidence supporting the close implication of the alteration in the splicing process in mammary tumorigenesis.

Epigenetic restoration and activation of ERβ: an inspiring approach for treatment of triple-negative breast cancer

BACKGROUND

Triple-negative breast cancer (TNBC) is one of the most aggressive subtypes of breast cancer. TNBC lacks targeted therapy receptors, rendering endocrine and HER2-targeted therapies ineffective. TNBC is typically treated with cytotoxic chemotherapy followed by surgery. Targeting epigenetic modifications could potentially be a new effective TNBC target therapy. The aim of this study is to examine the effects of epigenetic drugs, decitabine as DNA methyltransferase inhibitor (DNMTI) and vorinostat as histone deacetylase inhibitor (HDACI), and the ERβ agonist DPN on ERα and ERβ re-expressions in the MDA-MB-231 cells as a model of TNBC.

METHODS

Using MTT assay, the IC50 of decitabine, vorinostat, and DPN on MDA-MB-231 cells were determined. The effects of all drugs alone or in combinations on MDA-MB-231 cells were evaluated. qRT-PCR was used to determine ERα & ERβ gene expression. Caspase-3 activity and the protein expression levels of VEGF, Cyclin D1, and IGF-1 were assessed.

RESULTS

Both ERα and ERβ mRNA were re-expressed in different high levels in all treated groups, especially in the triple therapy group compared with control. Significantly, the triple drugs therapy showed the lowest levels of VEGF, Cyclin D1, and IGF-1 and the highest level of Caspase-3 activity, indicating a possible antitumor effect of ERβ activation through decreasing proliferation and angiogenesis and increasing apoptosis in MDA-MB-231 cells.

CONCLUSIONS

The antiproliferative effect of ERβ could be retained when co-expressed with Erα using a powerful epigenetic combination of Decitabine and vorinostat with DPN.

Correlation of prognostic factors of carcinoma breast with Ki 67 proliferation assay

Prognostic factors are important for the diagnosis of breast cancer as it helps in identification of high risk patients.  The objective of the study is to assess the proliferation index, Ki-67 and correlate it with other markers. The present study was a cohort study conducted in the Department of General Surgery at Tertiary Care Teaching Hospital over a period of 1 year with a sample size of 98. All the patients meeting the inclusion and exclusion criteria are recruited sequentially by convenient sampling until the sample size is attained, with the agreement of the institutional ethics committee. A total of 98 patients with a mean age of 53.61 ± 12.48 years were studied in the final analysis. The mean duration of lump was 4.62 ± 2.18 months and only 6.12% had the complaint of pain.  Majority of them had stage IIIB carcinoma at 43.88%, followed by stage IIA at 27.55%, 15.31% stage IIB, 13.27% stage IIIA.  At cut off 20, 69(70.40%) had ki67 proliferation index ≥20 and 29(29.59%) had<20. Correlation of Ki-67 Index with expression of estrogen receptor status had a p value of 0.019 and with progesterone receptor status, p 0.003 which was significant. 

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.

Estrogens and Progestogens in Triple Negative Breast Cancer: Do They Harm?

Triple-negative breast cancers (TNBC) occur more frequently in younger women and do not express estrogen receptor (ER) nor progesterone receptor (PR), and are therefore often considered hormone-insensitive. Treatment of premenopausal TNBC patients almost always includes chemotherapy, which may lead to premature ovarian insufficiency (POI) and can severely impact quality of life. Hormone replacement therapy (HRT) is contraindicated for patients with a history of hormone-sensitive breast cancer, but the data on safety for TNBC patients is inconclusive, with a few randomized trials showing increased risk-ratios with wide confidence intervals for recurrence after HRT. Here, we review the literature on alternative pathways from the classical ER/PR. We find that for both estrogens and progestogens, potential alternatives exist for exerting their effects on TNBC, ranging from receptor conversion, to alternative receptors capable of binding estrogens, as well as paracrine pathways, such as RANK/RANKL, which can cause progestogens to indirectly stimulate growth and metastasis of TNBC. Finally, HRT may also influence other hormones, such as androgens, and their effects on TNBCs expressing androgen receptors (AR). Concluding, the assumption that TNBC is completely hormone-insensitive is incorrect. However, the direction of the effects of the alternative pathways is not always clear, and will need to be investigated further.

Insights into the Role of Estrogen Receptor β in Triple-Negative Breast Cancer

Estrogen receptors (ERα and ERβ) are ligand-activated transcription factors that play different roles in gene regulation and show both overlapping and specific tissue distribution patterns. ERβ, contrary to the oncogenic ERα, has been shown to act as an oncosuppressor in several instances. However, while the tumor-promoting actions of ERα are well-known, the exact role of ERβ in carcinogenesis and tumor progression is not yet fully understood. Indeed, to date, highly variable and even opposite effects have been ascribed to ERβ in cancer, including for example both proliferative and growth-inhibitory actions. Recently ERβ has been proposed as a potential target for cancer therapy, since it is expressed in a variety of breast cancers (BCs), including triple-negative ones (TNBCs). Because of the dependence of TNBCs on active cellular signaling, numerous studies have attempted to unravel the mechanism(s) behind ERβ-regulated gene expression programs but the scenario has not been fully revealed. We comprehensively reviewed the current state of knowledge concerning ERβ role in TNBC biology, focusing on the different signaling pathways and cellular processes regulated by this transcription factor, as they could be useful in identifying new diagnostic and therapeutic approaches for TNBC.

Role of 17β-Estradiol on Cell Proliferation and Mitochondrial Fitness in Glioblastoma Cells

Gliomas are the most common primary tumors of the central nervous system (CNS) in the adult. Previous data showed that estrogen affects cancer cells, but its effect is cell-type-dependent and controversial. The present study aimed to analyze the effects of estradiol (E2, 5 nM) in human glioblastoma multiforme U87-MG cells and how it may impact on cell proliferation and mitochondrial fitness. We monitored cell proliferation by xCELLigence technology and mitochondrial fitness by assessing the expression of genes involved in mitochondrial biogenesis (PGC1α, SIRT1, and TFAM), oxidative phosphorylation (ND4, Cytb, COX-II, COX IV, NDUFA6, and ATP synthase), and dynamics (OPA1, MNF2, MNF1, and FIS1). Finally, we evaluated Nrf2 nuclear translocation by immunocytochemical analysis. Our results showed that E2 resulted in a significant increase in cell proliferation, with a significant increase in the expression of genes involved in various mechanisms of mitochondrial fitness. Finally, E2 treatment resulted in a significant increase of Nrf2 nuclear translocation with a significant increase in the expression of one of its target genes (i.e., heme oxygenase-1). Our results suggest that E2 promotes proliferation in glioblastoma cells and regulate the expression of genes involved in mitochondrial fitness and chemoresistance pathway.

Aberrant alternative splicing in breast cancer

Alternative splicing is critical for human gene expression regulation, which plays a determined role in expanding the diversity of functional proteins. Importantly, alternative splicing is a hallmark of cancer and a potential target for cancer therapeutics. Based on the statistical data, breast cancer is one of the top leading causes of cancer-related deaths in women worldwide. Strikingly, alternative splicing is closely associated with breast cancer development. Here, we seek to provide a general review of the relationship between alternative splicing and breast cancer. We introduce the process of alternative splicing and its regulatory role in cancers. In addition, we highlight the functions of aberrant alternative splicing and mutations of splicing factors in breast cancer progression. Moreover, we discuss the role of alternative splicing in cancer drug resistance and the potential of being targets for cancer therapeutics.

Characteristics, behaviour and role of biomarkers in metastatic triple-negative breast cancer

AIMS

Characterising the factors responsible for metastatic triple-negative breast cancer (TNBC) is of significant importance, considering its high mortality rate and scant data. In this study, we evaluated the characteristics, clinical behaviour and role of biomarkers (androgen receptor (AR), oestrogen receptor beta (ERβ) and p53) in metastatic TNBC.

METHODS

Immunohistochemistry was performed for AR, ERβ and p53 on 125 primary TNBCs with known metastasis and correlated with clinicopathological parameters and outcome. AR and p53 mRNA profiling was also carried out on 34 tumours from the same series and correlated with outcomes.

RESULTS

In this cohort, grade 3 and pT2 tumours predominated. The most common site for metastasis was the lung and pleura (41, 32.8%), and 15 (12.0%) cases demonstrated metastasis in multiple sites. Among these, 92% of tumours metastasised without preceding local recurrences. Five- and ten-year overall survival (OS) rates were 27% and 7.2%, while 5- and 10- year survival rates after metastasis were 9.6% and 3.2% respectively. AR, ERβ and p53 protein expressions were observed in 16%, 96.8% and 58.1% of tumours, respectively. A combinational phenotype of AR-ERβ+p53+ tumours was associated with poorer OS (HR 1.543, 95%CI 1.030 to 2.310, p=0.035). Higher AR mRNA levels were significantly associated with favourable OS (p=0.015) and survival after metastasis (p=0.027).

CONCLUSIONS

Metastatic TNBC harboured aggressive behaviour and displayed predominantly visceral metastasis with most metastatic events occurring without intervening local recurrences. A combinational phenotype of AR-ERβ+p53+ was significantly associated with poorer OS.

Implication of environmental estrogens on breast cancer treatment and progression

Breast cancer is the most diagnosed malignancy among women in the United States. Approximately 70% of breast tumors express estrogen receptor alpha and are deemed ER-positive. ER-positive breast tumors depend upon endogenous estrogens to promote ER-mediated cellular proliferation. Decades of research have led to a fundamental understanding of the role ER signaling in this disease and this knowledge has led to significant advancements in the clinical use of antiestrogens for breast cancer treatment. However, adjuvant breast cancer recurrence and metastatic disease progression due to endocrine therapy resistance are prominent and unresolved issues. The established role that estrogens play in breast cancer pathogenesis explains why some patients initially respond to endocrine therapy but also why a significant number of patients become refractory to antiestrogen treatment. It is been hypothesized that exposure to environmental steroid hormone mimics and/or acquired mechanisms of resistance may explain why endocrine therapy fails in a subset of breast cancer patients. This review will highlight: 1) the relationship between ER signaling and breast cancer pathogenesis, 2) the implication of environmental exposures on steroid hormone regulated processes including breast cancer, and 3) the unresolved issue of endocrine therapy resistance.

Differential Effects of Estrogen Receptor β Isoforms on Glioblastoma Progression

The estrogen receptor β (ERβ) functions as a tumor suppressor in glioblastoma (GBM) cells. However, the in vivo significance of endogenous ERβ and the roles of its isoforms in GBM are incompletely understood. Using ERβ isoform-specific PCR screening, we found that GBM cells predominantly express ERβ1 and ERβ5, along with low levels of ERβ2 and ERβ4. We observed greater ERβ5 expression in higher grades of glioma than in lower grades. In CRISPR-based ERβ knockout (KO) cells and ERβ KO cells uniquely expressing ERβ1 or ERβ5 only, ERβ1 significantly reduced proliferation. Compared with parental GBM cells, ERβ KO cells exhibited high migratory and invasive potentials, and reexpression of ERβ1 resulted in the reduction of this phenotype. Interestingly, ERβ5 expression increased foci formation and anchorage-independent growth of NIH3T3 cells and increased motile structure formation, including filopodia and ruffles in GBM cells. Only ERβ1-expressing tumors resulted in longer mouse survival. RNA-Seq analysis revealed unique pathways modulated by ERβ1 and ERβ5. Compared with ERβ KO cells, ERβ1 cells exhibited lower activation of mTOR signaling molecules, including p-mTOR, p-S6K, and p-S6, and ERβ5-expressing cells had enhanced mTOR downstream signaling. Unique proteins including several that function as regulators of mTOR, immunomodulatory, and apoptosis pathways bound to ERβ1 and ERβ5 isoforms. Our work confirms the tumor-suppressive potential of ERβ1 and reveals the acquired oncogenic ability of ERβ5 in GBM cells. ERβ isoform status and their unique interactions with oncogenic pathways may have important implications in GBM progression.Significance: These findings suggest that only ERβ isoform 1 has tumor suppressor function in GBM and that ERβ isoform switching contributes to GBM progression. Cancer Res; 78(12); 3176-89. ©2018 AACR.

The ERβ4 variant induces transformation of the normal breast mammary epithelial cell line MCF-10A; the ERβ variants ERβ2 and ERβ5 increase aggressiveness of TNBC by regulation of hypoxic signaling

Triple negative breast cancer (TNBC) still remains a challenge to treat in the clinic due to a lack of good targets for treatment. Although TNBC lacks expression of ERα, the expression of ERβ and its variants are detected quite frequently in this cancer type and can represent an avenue for treatment. We show that two of the variants of ERβ, namely ERβ2 and ERβ5, control aggressiveness of TNBC by regulating hypoxic signaling through stabilization of HIF-1α. RNA-seq of patient derived xenografts (PDX) from TNBC shows expression of ERβ2, ERβ4 and ERβ5 variants in more than half of the samples. Furthermore, expression of ERβ4 in the immortalized, normal mammary epithelial cell line MCF-10A that is resistant to tumorsphere formation caused transformation and development of tumorspheres. By contrast, ERβ1, ERβ2 or ERβ5 were unable to support tumorsphere formation. We have previously shown that all variants except ERβ1 stabilize HIF-1α but only ERβ4 appears to have the ability to transform normal mammary epithelial cells, pointing towards a unique property of ERβ4. We propose that ERβ variants may be good diagnostic tools and also serve as novel targets for treatment of breast cancer.

Estrogen receptor β2 induces proliferation and invasiveness of triple negative breast cancer cells: association with regulation of PHD3 and HIF-1α

The two estrogen receptor (ER) subtypes, ERα and ERβ, belong to the nuclear receptor superfamily. The human ERβ variant ERβ2 is proposed to be expressed at higher levels than ERβ1 in many breast tumors and it has been suggested that ERβ2, in contrast to ERβ1, is associated with aggressive phenotypes of various cancers. However, the role of endogenous ERβ2 in breast cancer cells remains elusive. In this study, we identified that triple negative breast cancer (TNBC) cell lines express endogenous ERβ2, but not ERα or ERβ1. This allows novel studies of endogenous ERβ2 functions independent of ERα and ERβ1. We show that overexpression of ERβ2 in TNBC cells increased whereas knockdown of endogenous ERβ2 decreased cell proliferation and cell invasion. To elucidate the molecular mechanism responsible for these cellular phenotypes, we assayed ERβ2 dependent global gene expression profiles. We show that ERβ2 decreases prolyl hydroxylase 3 (PHD3) gene expression and further show that this is associated with increased hypoxia inducible factor 1α (HIF-1α) protein levels, thus providing a possible mechanism for the invasive phenotype. These results are further supported by analysing the expression of ERβ2 and PHD3 in breast tumor samples where a negative correlation between ERβ2 and PHD3 expression was observed. Together, we demonstrate that ERβ2 has an important role in enhancing cell proliferation and invasion, beyond modulation of ERβ and ERβ1 signalling which might contribute to the invasive characteristics of TNBC. The invasive phenotype could potentially be mediated through transcriptional repression of PHD3 and increased HIF-1α protein levels.

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.

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.

Bisphenol A (BPA) Exposure In Utero Leads to Immunoregulatory Cytokine Dysregulation in the Mouse Mammary Gland: A Potential Mechanism Programming Breast Cancer Risk

Bisphenol-A (BPA) is a ubiquitous estrogen-like endocrine disrupting compound (EDC). BPA exposure in utero has been linked to breast cancer and abnormal mammary gland development in mice. The recent rise in incidence of human breast cancer and decreased age of first detection suggests a possible environmental etiology. We hypothesized that developmental programming of carcinogenesis may involve an aberrant immune response. Both innate and adaptive immunity play a role in tumor suppression through cytolytic CD8, NK, and Th1 T-cells. We hypothesized that BPA exposure in utero would lead to dysregulation of both innate and adaptive immunity in the mammary gland. CD1 mice were exposed to BPA in utero during gestation (days 9-21) via osmotic minipump. At 6 weeks, the female offspring were ovariectomized and estradiol was given at 8 weeks. RNA and protein were extracted from the posterior mammary glands, and the mRNA and protein levels were measured by PCR array, qRT-PCR, and western blot. In mouse mammary tissue, BPA exposure in utero significantly decreased the expression of members of the chemokine CXC family (Cxcl2, Cxcl4, Cxcl14, and Ccl20), interleukin 1 (Il1) gene family (Il1β and Il1rn), interleukin 2 gene family (Il7 receptor), and interferon gene family (interferon regulatory factor 9 (Irf9), as well as immune response gene 1 (Irg1). Additionally, BPA exposure in utero decreased Esr1 receptor gene expression and increased Esr2 receptor gene expression. In utero exposure of BPA resulted in significant changes to inflammatory modulators within mammary tissue. We suggest that dysregulation of inflammatory cytokines, both pro-inflammatory and anti-inflammatory, leads to a microenvironment that may promote disordered cell growth through inhibition of the immune response that targets cancer cells.

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.

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.