Estrogen receptor | EPFL Graph Search

Estrogen receptors (ERs) are a group of proteins found inside cells. They are receptors that are activated by the hormone estrogen (17β-estradiol). Two classes of ER exist: nuclear estrogen receptors (ERα and ERβ), which are members of the nuclear receptor family of intracellular receptors, and membrane estrogen receptors (mERs) (GPER (GPR30), ER-X, and Gq-mER), which are mostly G protein-coupled receptors. This article refers to the former (ER). Once activated by estrogen, the ER is able to translocate into the nucleus and bind to DNA to regulate the activity of different genes (i.e. it is a DNA-binding transcription factor). However, it also has additional functions independent of DNA binding. As hormone receptors for sex steroids (steroid hormone receptors), ERs, androgen receptors (ARs), and progesterone receptors (PRs) are important in sexual maturation and gestation. Proteomics There are two different forms of the estrogen receptor, usually referred to as α and β, eac

In vivo investigation of estrogenic activity by fluorescence techniques

Hanna Jankevics

Hormone binding nuclear receptors are transcription factors that activate gene transcription by binding to specific DNA sequences in the gene promoter region and then recruiting the necessary coactivator proteins for transcriptional activation. The knowledge of the function of these receptors, e.g. how they activate or repress transcription are deduced mainly from in vitro biochemical experiments. A general model has been proposed that these receptors and the recruited coactivator proteins form relatively stable complexes with gene promoters. Only recently, in the last four years, additional in vivo data measured with fluorescence recovery after photobleaching (FRAP) have shown that many hormone receptors and coactivators are very mobile inside the nucleus and their association to chromatin is very dynamic, much faster than what has been anticipated from earlier biochemical studies. Although the mobility is reported to be high for the hormone binding receptors, there are consistent reports about reduced mobility in the presence of agonists and antagonists. However, little is known about the significance of the altered mobility. Open questions are, whether the change of mobility is due to increasing interactions with other proteins, e.g. by forming larger protein complexes or if it is due to interactions with chromatin and other relative immobile domains of the nucleus. In this work, fluorescence correlation spectroscopy (FCS) has been employed to monitor the mobility of both a hormone binding receptor, the estrogen receptor (ER), and coactivator proteins belonging to the steroid receptor coactivator (SRC)-family inside the nucleus, to investigate how their mobility is influenced by different ligands. The main advantages of FCS compared to FRAP are (i) its sensitivity which enables measurements of proteins of low abundance in live cells and (ii) its higher temporal resolution which allows us to resolve different diffusing species in the millisecond range. This work has been divided into four major parts. The first contains the construction and characterization of activity of fluorescently labeled molecules. The second part describes the optimization of the experimental conditions for measuring the mobility of yellow fluorescent protein (YFP) in living cells. The third part reports on the effects of YFP-labeled ER inside the nucleus in the presence of different ligands. Finally the fourth part investigates the effects of different ligands on the interaction between receptor and coactivator in living cells. The main results of this thesis are the following: The finding of the different mobility patterns of YFP-ER in the presence of agonists and antagonists indicate that the different ligands induce multiple discrete diffusive states; some are re-occuring for different ligands while others are characteristic for particular ligands. The potency of the different ligands to induce a lower mobility of the YFP-ER was estimated, and the relative order of the potencies to induce the lower mobility corresponds well to the relative order of their affinities for ER. ER and coactivator proteins were shown to interact in the absence of ligands and there are also clear indications of the co-existence of multiple ER-SRC complexes in the presence of agonists. The full antagonist abolishes these interactions completely in the case of the full-length coactivator and only partly when a truncated coactivator, containing only the receptor interaction domain, was used.

EPFL2004

Intraductal xenografts model estrogen receptor-positive (ER+) breast cancer dormancy and reveal a critical role for epithelial-mesenchymal transition (EMT) in its establishment

Patrik Aouad

Compared to estrogen receptor-negative (ER-) breast cancer (BC), ER+ BC often manifests with a latent disease that recurs decades after initial diagnosis. The mechanisms governing dormancy and distant recurrence of ER+ tumors remain elusive due to the lack of preclinical models. Here, we compared the tumor progression of ER+ and triple negative (TN; ER-, progesterone receptor and human epidermal growth factor receptor 2-negative) BCs by grafting cell lines- and patient-derived tumor cells into the milk ducts of immunocompromised mice. In the intraductal model, both ER+ and TN BC cells disseminate already during the in situ stage. TN disseminated tumor cells (DTCs) proliferate and form macro-metastases, while DTCs from ER+ BC xenografts have low proliferative indices, are arrested in the G0/G1 phase of the cell cycle, and express the dormancy marker p27. Dormant DTCs display mesenchymal and niche-specific characteristics, as revealed by three-dimensional single cell resolution imaging, and show molecular features of Epithelial-Mesenchymal Transition (EMT) with decreased CDH1, and in-creased ZEB1, ZEB2, and VIM expression levels. Surprisingly, EMT is neither detected in primary tumor cells, nor required for their invasion or dissemination, but is acquired upon their establishment in distant sites. In ex vivo cultures, dormant lung and brain DTCs, revert back to a proliferative state within 3 weeks through a Mesenchymal-Epithelial Transition (MET). In vivo, CDH1 restoration in dormant DTCs overcomes dormancy and increases the growth and proliferation of lung metastases, while decreasing the expression of EMT-transcription factors (MET). We conclude that the intraductal model provides exciting new experimental opportunities to study ER+ BC metastasis dormancy, and reveals that EMT could be exploited therapeutically to promote dormancy and prevent distant recurrence.

EPFL2021

Epithelial-mesenchymal plasticity determines estrogen receptor positive breast cancer dormancy and epithelial reconversion drives recurrence

Giovanna Ambrosini, Patrik Aouad, Cathrin Brisken, Fabio De Martino, Kelly Spry Maggs, Hazel Margaret Quinn, Georgios Sflomos, Céline Marie Victoria Stibolt, Yueyun Zhang

More than 70% of human breast cancers (BCs) are estrogen receptor α-positive (ER+). A clinical challenge of ER+ BC is that they can recur decades after initial treatments. Mechanisms governing latent disease remain elusive due to lack of adequate in vivo models. We compare intraductal xenografts of ER+ and triple-negative (TN) BC cells and demonstrate that disseminated TNBC cells proliferate similarly as TNBC cells at the primary site whereas disseminated ER+ BC cells proliferate slower, they decrease CDH1 and increase ZEB1,2 expressions, and exhibit characteristics of epithelial-mesenchymal plasticity (EMP) and dormancy. Forced E-cadherin expression overcomes ER+ BC dormancy. Cytokine signalings are enriched in more active versus inactive disseminated tumour cells, suggesting microenvironmental triggers for awakening. We conclude that intraductal xenografts model ER + BC dormancy and reveal that EMP is essential for the generation of a dormant cell state and that targeting exit from EMP has therapeutic potential.

2022