Influence of Cellular ER /ER Ratio on the ER -Agonist Induced Proliferation of Human T47D Breast Cancer Cells (original) (raw)
Related papers
2008
Breast cancer cells show overexpression of estrogen receptor (ER) a relative to ERb compared to normal breast tissues. This observation has lead to the hypothesis that ERb may modulate the proliferative effect of ERa. This study investigated how variable cellular expression ratios of the ERa and ERb modulate the effects on cell proliferation induced by ERa or ERb agonists, respectively. Using human osteosarcoma (U2OS) ERa or ERb reporter cells, propyl-pyrazole-triol (PPT) was shown to be a selective ERa and diarylpropionitrile (DPN) a preferential ERb modulator. The effects of these selective estrogen receptor modulators (SERMs) and of the model compound E2 on the proliferation of T47D human breast cancer cells with tetracyclinedependent expression of ERb (T47D-ERb) were characterized. E2-induced cell proliferation of cells in which ERb expression was inhibited was similar to that of the T47D wild-type cells, whereas this E2-induced cell proliferation was no longer observed when ERb expression in the T47D-ERb cells was increased. In the T47D-ERb cell line, DPN also appeared to be able to suppress cell proliferation when levels of ERb expression were high. In the T47D-ERb cell line, PPT was unable to suppress cell proliferation at all ratios of ERa/ERb expression, reflecting its ability to activate only ERa and not ERb. It is concluded that effects of estrogen-like compounds on cell proliferation are dependent on the actual ERa/ERb expression levels in these cells or tissues and the potential of the estrogen agonists to activate ERa and/or ERb.
2008
Breast cancer cells show overexpression of estrogen receptor (ER) a relative to ERb compared to normal breast tissues. This observation has lead to the hypothesis that ERb may modulate the proliferative effect of ERa. This study investigated how variable cellular expression ratios of the ERa and ERb modulate the effects on cell proliferation induced by ERa or ERb agonists, respectively. Using human osteosarcoma (U2OS) ERa or ERb reporter cells, propyl-pyrazole-triol (PPT) was shown to be a selective ERa and diarylpropionitrile (DPN) a preferential ERb modulator. The effects of these selective estrogen receptor modulators (SERMs) and of the model compound E2 on the proliferation of T47D human breast cancer cells with tetracyclinedependent expression of ERb (T47D-ERb) were characterized. E2-induced cell proliferation of cells in which ERb expression was inhibited was similar to that of the T47D wild-type cells, whereas this E2-induced cell proliferation was no longer observed when ERb...
Maturitas, 2014
Objective: Local application of estradiol (E2) to treat vulvovaginal atrophy in postmenopausal breast cancer patients receiving aromatase inhibitors is known to elevate serum estradiol levels and thereby might counteract breast cancer therapy. Thus, vaginal application of estriol (E3) has been recommended for these patients. However, it is unclear to what extent E3 stimulates breast cancer cell growth. In this study, we examined the effect of E3 on growth and gene expression of two human breast cancer cell lines. Methods: We used an established in vitro cell culture assay and compared the effect of E2 and E3 on growth of the estrogen receptor alpha-positive breast cancer cell lines MCF-7 and T-47D testing a wide range of hormone concentrations of 10 −12-10 −7 M. E3 effects on gene expression were examined by means of reporter gene assays, RT-qPCR and Western blot analysis. Results: E3 acted as a potent estrogen and exerted a mitogenic effect on T-47D and MCF-7 cells at concentrations of 10 −9 M (288 pg/ml) and higher. With regard to activation of an estrogen response element (ERE) in breast cancer cells, effects of E3 were visible at 10 −10 M. The same concentrations of E3 activated expression of the estrogen-responsive gene PR and of the proliferation genes cyclin A2, cyclin B1, Ki-67, c-myc and b-myb, providing molecular mechanisms underlying the observed growth increase. Conclusions: Like E2, low levels of E3 were able to trigger a robust estrogenic response in breast cancer cells. Thus, our data suggest caution regarding use of E3 by breast cancer survivors.
Oncogene, 2005
The mitogenic effect of 17b-estradiol (E2) on the breast is mediated by estrogen receptor alfa (ERa), hence ERa antagonists are effective in the treatment of breast cancer. The possible use of estrogen receptor beta (ERb) as a target in treatment of breast cancer is under investigation. The mouse mammary cell line HC11 expresses both ERs and was used to study the role of the two receptors in proliferation. E2 had no effect on proliferation. The ERaselective agonist 4,4 0 ,4 00 -(4-propyl-(1H)-pyrazole-1,3,5triyl)trisphenol (PPT) stimulated proliferation. The ERb-selective agonist 2,3-bis(4-hydroxy-phenyl)-propionitrile (DPN) inhibited cell growth and induced apoptosis. PPT upregulated while DPN downregulated cyclin D1 and proliferating cell nuclear antigen (PCNA). Upon inhibition of ERa expression with RNA interference, E2 caused a decrease in cyclin D1 and PCNA, and increased apoptosis. When ERb expression was blocked, E2 induced proliferation and cells gained the capacity to grow in soft agar. In summary, in HC11 mammary epithelial cells, ERa drives proliferation in response to E2 while ERb is growth inhibitory. The lack of effect of E2 on HC11 cell growth is the result of the combined actions of ERa (proliferation) and ERb (apoptosis). We suggest that use of ERb agonists will be a useful addition in treatment of breast cancer, which, at present, is only aimed at inhibition of ERa. Oncogene (2005) 24, 6605-6616.
PLOS One, 2012
Estrogens play essential roles in the progression of mammary and prostatic diseases. The transcriptional effects of estrogens are transduced by two estrogen receptors, ERa and ERb, which elicit opposing roles in regulating proliferation: ERa is proliferative while ERb is anti-proliferative. Exogenous expression of ERb in ERa-positive cancer cell lines inhibits cell proliferation in response to estrogen and reduces xenografted tumor growth in vivo, suggesting that ERb might oppose ERa's proliferative effects via formation of ERa/b heterodimers. Despite biochemical and cellular evidence of ERa/b heterodimer formation in cells co-expressing both receptors, the biological roles of the ERa/b heterodimer remain to be elucidated. Here we report the identification of two phytoestrogens that selectively activate ERa/b heterodimers at specific concentrations using a cell-based, two-step high throughput small molecule screen for ER transcriptional activity and ER dimer selectivity. Using ERa/b heterodimer-selective ligands at defined concentrations, we demonstrate that ERa/b heterodimers are growth inhibitory in breast and prostate cells which co-express the two ER isoforms. Furthermore, using Automated Quantitative Analysis (AQUA) to examine nuclear expression of ERa and ERb in human breast tissue microarrays, we demonstrate that ERa and ERb are co-expressed in the same cells in breast tumors. The co-expression of ERa and ERb in the same cells supports the possibility of ERa/b heterodimer formation at physio-and pathological conditions, further suggesting that targeting ERa/b heterodimers might be a novel therapeutic approach to the treatment of cancers which coexpress ERa and ERb.
PLoS ONE, 2012
Estrogens play essential roles in the progression of mammary and prostatic diseases. The transcriptional effects of estrogens are transduced by two estrogen receptors, ERa and ERb, which elicit opposing roles in regulating proliferation: ERa is proliferative while ERb is anti-proliferative. Exogenous expression of ERb in ERa-positive cancer cell lines inhibits cell proliferation in response to estrogen and reduces xenografted tumor growth in vivo, suggesting that ERb might oppose ERa's proliferative effects via formation of ERa/b heterodimers. Despite biochemical and cellular evidence of ERa/b heterodimer formation in cells co-expressing both receptors, the biological roles of the ERa/b heterodimer remain to be elucidated. Here we report the identification of two phytoestrogens that selectively activate ERa/b heterodimers at specific concentrations using a cell-based, two-step high throughput small molecule screen for ER transcriptional activity and ER dimer selectivity. Using ERa/b heterodimer-selective ligands at defined concentrations, we demonstrate that ERa/b heterodimers are growth inhibitory in breast and prostate cells which co-express the two ER isoforms. Furthermore, using Automated Quantitative Analysis (AQUA) to examine nuclear expression of ERa and ERb in human breast tissue microarrays, we demonstrate that ERa and ERb are co-expressed in the same cells in breast tumors. The co-expression of ERa and ERb in the same cells supports the possibility of ERa/b heterodimer formation at physio-and pathological conditions, further suggesting that targeting ERa/b heterodimers might be a novel therapeutic approach to the treatment of cancers which coexpress ERa and ERb.
Estrogen receptor beta exerts growth-inhibitory effects on human mammary epithelial cells
Breast Cancer Research and Treatment, 2009
Estrogen receptor b (ERb) is widely expressed in mammary epithelium. ERb expression is reported to decline during carcinogenesis of the breast and other tissues. In this study, we examined the consequences of a loss of ERb expression in mammary epithelial cells. We knocked down ERb transcript levels in human mammary epithelial MCF-10A cells and in MCF-7 breast cancer cells by means of stable transfection with a specific shRNA plasmid. ERb knockdown resulted in a significant growth increase of both cell types in a ligand-independent manner. This effect was accompanied by elevated cyclin A2 expression in MCF-10A cells and by decreased expression of growth-inhibitory p21/ WAF and epithelial cell marker cytokeratine 8 in both cell lines. Transfection of ERb shRNA did not alter the absent proliferative estrogen response of MCF-10A cells, but conferred sensitivity to selective estrogen receptor modulator tamoxifen to this cell line. In contrast, ERb knockdown diminished estrogen responsiveness of MCF-7 breast cancer cells and also weakened the effect of tamoxifen on this cell line. These ligand-dependent effects only observed in MCF-7 cells exhibiting a high ERa/b ratio were accompanied by smaller estrogenic repression of p21/WAF expression, an impaired tamoxifen-triggered induction of this gene and by relative downregulation of ERa and cyclin A2 transcript levels. Our data suggest that ERb exerts antiproliferative effects both on MCF-10A and MCF-7 cells in a ligand-and ERa-independent manner by regulation of p21/WAF or cyclin A2 gene expression. Knockdown of ERb in both cell types was sufficient to significantly decrease transcript levels of epithelial cell marker cytokeratin 8. The results of this study support the hypothesis that ERb acts as a tumor suppressor in mammary epithelium.
Archives of Gynecology and Obstetrics, 2013
Introduction Coexpression of estrogen receptors (ER) a and b is present in about half of all breast cancer cases. Whereas ERa is a well-established target for endocrine therapy with the selective estrogen receptor modulator tamoxifen, the applicability of ERb as target in breast cancer therapy is unclear. In this study, we examined the effects of two synthetic ERb agonists alone and in combination with tamoxifen on ERa/b-positive breast cancer cells. Methods We treated MCF-7 and T-47D breast cancer cells with the ERb agonists ERB-041 and WAY-200070 and measured the effects on cell growth. In addition, transcriptome analyses were performed by means of Affymetrix GeneChip arrays. Results When given alone, ERb agonists ERB-041 and WAY-200070 did not affect the growth of MCF-7 or T-47D cells. In contrast, addition of these drugs to tamoxifen increased its growth-inhibitory effect on both cell lines. This effect was more pronounced under serumfree conditions, but was also observed in the presence of serum in T-47D cells. Transcriptome analyses revealed a set of genes regulated after addition of ERb agonists including S100A8 and CD177. Conclusion The observed enhanced growth-inhibitory effects of a combination of tamoxifen and ERb agonists in vitro encourage further studies to test its possible use in the clinical setting.
Regulation of specific target genes and biological responses by estrogen receptor subtype agonists
Current Opinion in Pharmacology, 2010
Estrogenic effects are mediated through two estrogen receptor (ER) subtypes, ERa and ERb. Estrogens are the most commonly prescribed drugs to treat menopausal conditions, but by non-selectively triggering both ERa and ERb pathways in different tissues they can cause serious adverse effects. The different sizes of the binding pockets and sequences of their activation function domains indicate that ERa and ERb should have different specificities for ligands and biological responses that can be exploited for designing safer and more selective estrogens. ERa and ERb regulate different genes by binding to different regulatory elements and recruiting different transcription and chromatin remodeling factors that are expressed in a cell-specific manner. ERa-selective and ERbselective agonists have been identified that demonstrate that the two ERs produce distinct biological effects. ERa and ERb agonists are a promising new approach for treating specific conditions associated with menopause.