Impact of Estrogen Receptor β on Gene Networks Regulated by Estrogen Receptor α in Breast Cancer Cells

Department of Cell and Developmental Biology, University of Illinois, Urbana-Champaign, Urbana, Illinois, United States
Endocrinology (Impact Factor: 4.5). 11/2006; 147(10):4831-42. DOI: 10.1210/en.2006-0563
Source: PubMed


Two subtypes of the estrogen receptor (ER), ERalpha and ERbeta, mediate the actions of estrogens, and although 70% of human breast cancers express ERbeta along with ERalpha, little is known about the possible comodulatory effects of these two ERs. To investigate this, we have used adenoviral gene delivery to produce human breast cancer (MCF-7) cells expressing different levels of ERbeta, along with their endogenous ERalpha, and have examined the effects of ERbeta and receptor occupancy, using ER subtype selective ligands, on genome-wide gene expression by microarray and pathway network analysis. ERbeta had diverse effects on gene expression, enhancing or counteracting ERalpha regulation for distinct subsets of estrogen target genes. Strikingly, ERbeta in the absence of estradiol (E2), elicited the stimulation or suppression of many genes that were normally only regulated by ERalpha with E2. In addition, ERbeta plus E2 elicited the expression of a unique group of genes that were not regulated by ERalpha plus E2 alone. The expression of genes in many functional categories were modulated by ERbeta, with the greatest numbers associated with transcription factors and signal transduction pathways. Regulation of multiple components in the TGFbeta and semaphorin pathways, and of genes controlling cell cycle progression and apoptosis, may contribute to the suppression of cell proliferation observed with ERbeta. Our observations suggest that the relative levels of ERbeta and ERalpha in breast cancers are likely to impact cell proliferation and the activities of diverse signaling pathways and their response to ER ligands and endocrine therapies.

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    • "indicate partly overlapping transcriptomes induced by the two ER subtypes (Chang et al, 2006). However, experimental studies in vitro and during tumour xenograft growth have shown opposing roles of the two receptors in terms of proliferation (Ström et al, 2004; Hartman et al, 2006). "
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    ABSTRACT: Background: The expression of oestrogen receptor (ER) α characterises a subset of breast cancers associated with good response to endocrine therapy. However, the clinical significance of the second ER, ERβ1, and its splice variant ERβcx is still unclear. Methods: We here report an assessment of ERα, ERβ1 and ERβcx by immunohistochemistry using quantitative digital image analysis of 340 primary tumours and corresponding sentinel lymph nodes. Results: No differences were seen in ER levels in primary tumours vs lymph node metastases. ERβ1 and ERβcx were equally distributed among age groups and tumour histological grades. Loss of ERβ1 in the primary tumour was strongly associated with poor survival. Its prognostic impact was particularly evident in young patients and in high-grade tumours. The worst outcome was seen in the tumours lacking both ERα and ERβ1. ERβcx expression in the primary tumour correlated with a higher risk of lymph node metastasis, and with poor survival when expressed in sentinel node lymphocytes. Conclusions: Our study reveals highly significant although antagonising roles of ERβ1 and ERβcx in breast cancer. Consequently, we suggest that the histopathological assessment of ERβ1 is of value as a prognostic and potentially predictive biomarker.
    British Journal of Cancer 07/2014; 111(5). DOI:10.1038/bjc.2014.398 · 4.84 Impact Factor
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    • "ER beta has been shown to inhibit human breast cancer cell proliferation by repressing transcription of the c-myc, cyclin D1 and cyclin A genes and increasing the expression of the cyclin-dependent kinase inhibitors p21Waf1/Cip1 and p27Kip1, leading to cell cycle arrest in the G2 phase [5,40,61]. Moreover, p21 up-regulation and cyclin D1 down-regulation have been identified as important events able to mediate AR signaling [25,41]. "
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    ABSTRACT: The two isoforms of estrogen receptor (ER) alpha and beta play opposite roles in regulating proliferation and differentiation of breast cancers, with ER-alpha mediating mitogenic effects and ER-beta acting as a tumor suppressor. Emerging data have reported that androgen receptor (AR) activation inhibits ER-positive breast cancer progression mainly by antagonizing ER-alpha signaling. However, to date no studies have specifically evaluated a potential involvement of ER-beta in the inhibitory effects of androgens. ER-beta expression was examined in human breast cancer cell lines using real-time PCR, Western blotting and small interfering RNA (siRNA) assays. Mutagenesis studies, electromobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP) analysis were performed to assess the effects of mibolerone/AR on ER-beta promoter activity and binding. In this study, we demonstrate that mibolerone, a synthetic androgen ligand, up-regulates ER-beta mRNA and protein levels in ER-positive breast cancer cells. Transient transfection experiments, using a vector containing the human ER-beta promoter region, show that mibolerone increases basal ER-beta promoter activity. Site-directed mutagenesis and deletion analysis reveal that an androgen response element (ARE), TGTTCT motif located at positions -383 and -377, is critical for mibolerone-induced ER-beta up-regulation in breast cancer cells. This occurs through an increased recruitment of AR to the ARE site within the ER-beta promoter region, along with an enhanced occupancy of RNA polymerase II. Finally, silencing of ER-beta gene expression by RNA interference is able to partially reverse the effects of mibolerone on cell proliferation, p21 and cyclin D1 expression. Collectively, these data provide evidence for a novel mechanism by which activated AR, through an up-regulation of ER-beta gene expression, inhibits breast cancer cell growth.
    Breast cancer research: BCR 02/2014; 16(1):R21. DOI:10.1186/bcr3619 · 5.49 Impact Factor
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    • "However, p27Kip1 is not regulated at the transcriptional level since its mRNA level does not change significantly in response to ERb1 (Hartman et al., 2009). Chang et al. showed that ERb1 regulated multiple components of TGFb signaling , consistent with the established role of TGFb in the suppression of breast cancer cell proliferation (Chang et al., 2006). Transplanting ERb1 expressing breast cancer cells into the mammary tissue of SCID/beige immunodeficient mice demonstrated inhibitory effects of ERb1 on tumor growth as well as "
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    ABSTRACT: 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.
    Molecular and Cellular Endocrinology 01/2014; 382(1):665–672. DOI:10.1016/j.mce.2013.08.005 · 4.41 Impact Factor
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