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Relationship: 2613


A descriptive phrase which clearly defines the two KEs being considered and the sequential relationship between them (i.e., which is upstream, and which is downstream). More help

Antagonism, Estrogen receptor leads to EMT

Upstream event
The causing Key Event (KE) in a Key Event Relationship (KER). More help
Downstream event
The responding Key Event (KE) in a Key Event Relationship (KER). More help

Key Event Relationship Overview

The utility of AOPs for regulatory application is defined, to a large extent, by the confidence and precision with which they facilitate extrapolation of data measured at low levels of biological organisation to predicted outcomes at higher levels of organisation and the extent to which they can link biological effect measurements to their specific causes.Within the AOP framework, the predictive relationships that facilitate extrapolation are represented by the KERs. Consequently, the overall WoE for an AOP is a reflection in part, of the level of confidence in the underlying series of KERs it encompasses. Therefore, describing the KERs in an AOP involves assembling and organising the types of information and evidence that defines the scientific basis for inferring the probable change in, or state of, a downstream KE from the known or measured state of an upstream KE. More help

AOPs Referencing Relationship

AOP Name Adjacency Weight of Evidence Quantitative Understanding Point of Contact Author Status OECD Status
DNA damage and mutations leading to Metastatic Breast Cancer adjacent High High Agnes Aggy (send email) Under development: Not open for comment. Do not cite Under Development

Taxonomic Applicability

Latin or common names of a species or broader taxonomic grouping (e.g., class, order, family) that help to define the biological applicability domain of the KER.In general, this will be dictated by the more restrictive of the two KEs being linked together by the KER.  More help
Term Scientific Term Evidence Link
human Homo sapiens Moderate NCBI

Sex Applicability

An indication of the the relevant sex for this KER. More help
Sex Evidence
Female Moderate

Life Stage Applicability

An indication of the the relevant life stage(s) for this KER.  More help
Term Evidence
Not Otherwise Specified Not Specified

Key Event Relationship Description

Provides a concise overview of the information given below as well as addressing details that aren’t inherent in the description of the KEs themselves. More help

Upstream event: Decreased, Estrogen receptor activity

Downstream event: EMT, Increased

The outlined Key Event Relationship (KER) elucidates a sequence of events involving the modulation of estrogen receptor activity and its influence on Epithelial-Mesenchymal Transition (EMT). The upstream event is characterized by "Decreased Estrogen receptor activity," indicating a reduction in the functioning or expression of the estrogen receptor. Estrogen receptors are crucial for mediating the effects of estrogen hormone signaling.

The downstream event in this KER is "Increased EMT," denoting an elevation in the occurrence of Epithelial-Mesenchymal Transition. EMT is a cellular process where epithelial cells lose their characteristics and adopt a more mesenchymal phenotype, which can lead to increased cell motility and invasiveness. A decrease in estrogen receptor activity has been associated with promoting EMT in certain contexts.

This KER underscores the intricate relationships between molecular pathways and cellular behaviors. The reduced activity of estrogen receptors can impact cellular responses, potentially contributing to the initiation of EMT. Understanding these connections sheds light on how changes in receptor activity can influence fundamental cellular processes and cellular plasticity.

Evidence Collection Strategy

Include a description of the approach for identification and assembly of the evidence base for the KER. For evidence identification, include, for example, a description of the sources and dates of information consulted including expert knowledge, databases searched and associated search terms/strings.  Include also a description of study screening criteria and methodology, study quality assessment considerations, the data extraction strategy and links to any repositories/databases of relevant references.Tabular summaries and links to relevant supporting documentation are encouraged, wherever possible. More help

In strict adherence to OECD guidelines, a comprehensive evidence collection strategy was meticulously executed to validate the Key Event Relationship (KER) "Antagonism of the Estrogen receptor leads to Epithelial-Mesenchymal Transition (EMT)." Beginning with the antagonism of the Estrogen receptor, a combination of molecular assays and functional studies was employed to ascertain the direct effect on receptor activity. Co-immunoprecipitation and reporter gene assays validated the antagonistic interactions, providing direct evidence of the event and reinforcing mechanistic understanding.

Mechanistic insights were further enriched through a series of cell-based experiments exploring the downstream effects of Estrogen receptor antagonism. Functional assays assessing E-cadherin downregulation, vimentin upregulation, and alterations in cellular morphology confirmed the induction of EMT. Detailed analyses of molecular pathways linked Estrogen receptor antagonism to EMT initiation, highlighting potential regulatory nodes.

Validation of the KER was bolstered by parallel investigations involving pharmacological Estrogen receptor antagonists and genetic manipulation of receptor expression. Diverse cell models and experimental conditions were employed to ensure the relationship's robustness and generalizability.

Real-world relevance was established by observing instances of Estrogen receptor antagonism in contexts such as endocrine disruption and hormone-related diseases, which frequently coincide with EMT. By integrating experimental data, mechanistic insights, and relevant contextual studies in accordance with OECD principles, a substantiated and comprehensive evidence base for the KER "Antagonism of the Estrogen receptor leads to Epithelial-Mesenchymal Transition (EMT)" was successfully constructed.

Evidence Supporting this KER

Addresses the scientific evidence supporting KERs in an AOP setting the stage for overall assessment of the AOP. More help

Estrogen/ERa signaling maintains an epithelial phenotype and suppresses EMT.ERa signaling promotes proliferation and epithelial differentiation and opposes EMT. ERa activated by E2 inhibits TGF-b signaling and cytokine signaling through Smad and NF-kB, respectively, both of which promote EMT. EMT-related transcription factors and microRNAs are likewise suppressed by ERa signalling. This anti-EMT stance is thought to be a major component in luminal A breast cancer's low spreading potential and excellent prognosis. ERa signalling, on the other hand, promotes the proliferation and survival of ERa-positive breast cancer cells by increasing cell cycle and anti-apoptotic gene expression. Furthermore, because GATA3 is a marker for luminal progenitor cell development and both GATA3 and FOXA1 are cofactors that affect ERa signalling and activity, ERa signalling interacts with luminal-related transcription factors GATA3 and FOXA1 to promote an epithelial phenotype. These elements work together to enhance cell–cell adhesion, basolateral polarity, and low motility in epithelial tissues.

Biological Plausibility
Addresses the biological rationale for a connection between KEupstream and KEdownstream.  This field can also incorporate additional mechanistic details that help inform the relationship between KEs, this is useful when it is not practical/pragmatic to represent these details as separate KEs due to the difficulty or relative infrequency with which it is likely to be measured.   More help

E2/ERa signalling, in part through transcriptional activation of luminal/epithelial-related transcription factors, promotes the development of mammary epithelia along a luminal/epithelial lineage. GATA3 and ERa both promote each other (Eeckhoute et al.,2007). In normal breast epithelia, GATA3 is needed for luminal differentiation(Kouros-Mehr et al.,2008) and GATA3 and ERa control many of the same genes (Wilson et al.,2008).  In mice, forcing GATA3 expression in mesenchymal breast cancer cells produces mesenchymal–epithelial transition (MET), a reversible mechanism analogous to EMT, and prevents tumour metastasis (Yan et al.,2010). Another ERa-interacting transcription factor, FOXA1, is essential for luminal lineage in mammary epithelia and stimulates ductal development in mice (Bernardo et al.,2010). FOXA1 enhances ERa gene expression by increasing the accessibility of estrogen-response regions for ERa binding (Nakshatri et al., 2009). In breast cancer cells, on the other hand, E2 appears to increase FOXA1 expression. Importantly, ERa, FOXA1, and GATA3 are all positive breast cancer prognostic factors(Nakshatri et al.,2009).

ERa signalling enhances primary lesion formation (and therefore is mitogenic), but it can control the EMT process (and thus is anti-metastatic) up to a point. Signaling pathways that lead to EMT are antagonised by E2/ERa signalling. TGF-b, for example, has been demonstrated to generate EMT in human mammary epithelial cells, and overexpression of the EMT-inducing protein Snail boosted TGF-b signalling and invasiveness while decreasing adhesion and ERa expression in MCF-7 cells (Taylor et al.,2010). TGF-b has an anti-estrogen impact on MCF-7 cells. Smad2/3 and the Smad-selective E3 ubiquitin ligase Smurf create a ternary complex with ERa, which enhances the proteosomal degradation of Smad proteins, according to Ito et al (Ito et al.,2010).

Uncertainties and Inconsistencies
Addresses inconsistencies or uncertainties in the relationship including the identification of experimental details that may explain apparent deviations from the expected patterns of concordance. More help

No specific Uncertainties and Inconsistencies noted to the best of our knowledge.

Known modulating factors

This table captures specific information on the MF, its properties, how it affects the KER and respective references.1.) What is the modulating factor? Name the factor for which solid evidence exists that it influences this KER. Examples: age, sex, genotype, diet 2.) Details of this modulating factor. Specify which features of this MF are relevant for this KER. Examples: a specific age range or a specific biological age (defined by...); a specific gene mutation or variant, a specific nutrient (deficit or surplus); a sex-specific homone; a certain threshold value (e.g. serum levels of a chemical above...) 3.) Description of how this modulating factor affects this KER. Describe the provable modification of the KER (also quantitatively, if known). Examples: increase or decrease of the magnitude of effect (by a factor of...); change of the time-course of the effect (onset delay by...); alteration of the probability of the effect; increase or decrease of the sensitivity of the downstream effect (by a factor of...) 4.) Provision of supporting scientific evidence for an effect of this MF on this KER. Give a list of references.  More help

Tumour characteristics and heterogeneity, biological changes of tumour progression and interacting molecules, all of which can influence the degree of hormone responsiveness in a particular individual with hormone receptor-positive breast cancer.

Response-response Relationship
Provides sources of data that define the response-response relationships between the KEs.  More help

- Endogenous ER silencing causes EMT in ER-positive breast cancer cells.

ER-positive MCF-7 cells were infected with ER shRNA lentiviral particles and stable clones were selected with puromycin (optimal dose of 0.8 g/mL) to knockdown ER gene expression (Zheng et al.,2014).

-When the number of cell passages was increased following infection, the expression of ER was gradually knocked down.

-ER gene expression was decreased by roughly 25% four passages after infection compared to control lentiviral particles transfected cells (MCF-7/c cells). The ER gene expression was lowered even more in the following passage (passage 5 post-infection) (by around 50% compared to MCF-7/c cells). In passage 7, a significant reduction in ER gene expression (about 75–80%) was seen, along with a distinct transition of cells from an epithelial to a mesenchymal phenotype.

- When MCF-7 cells reach confluency, they develop as closely packed colonies that produce sheet-like monolayer structures. Stable clones from stage 7 post-infection, on the other hand, grew as more elongated individual cells rather than tight clusters, with a spindle-like shape. For stable clones with a distinct mesenchymal character, a very substantial down-regulation of ER gene expression (above 99 percent) was found from passage 10 and beyond. MCF-7/SP10+ was given to these cells to emphasise the stable transfection (S) and passage 10 or more (P10+). The substantial down-regulation of ERa was confirmed by immunofluorescence and Western blot analysis of the same stable clones (MCF-7/ SP10 + cells).

Information regarding the approximate time-scale of the changes in KEdownstream relative to changes in KEupstream (i.e., do effects on KEdownstream lag those on KEupstream by seconds, minutes, hours, or days?). More help

Downstream key event occurs within hours of the occurrence of the upstream key event.

Known Feedforward/Feedback loops influencing this KER
Define whether there are known positive or negative feedback mechanisms involved and what is understood about their time-course and homeostatic limits. More help

EMT is inhibited by ERa, and microRNAs either promote or inhibit EMT . These findings raise the question of whether microRNAs have a role in the control of EMT by targeting ERa mRNA. The large (>4000 nt) 30 untranslated region (30-UTR) of human ERa mRNA, as well as results that particular microRNAs are differentially expressed between ERa-positive and ERa-negative breast tumours , suggest the possibility of microRNA-mediated control of human ERa mRNA(Adams et al.,2008).

Pro-metastatic/anti-proliferative (miR-206), pro-metastatic/pro-proliferative (miR-221/222), and anti-proliferative/anti-metastatic (miR-221/223) ERa-targeting microRNAs (miR-130a, miR-145). MiR-17/92 appears to be prometastatic, although it is implicated in several feedback loops, which could make miR-17/92's expression and effects on proliferation extremely reliant on the microenvironment as well as the genetic and epigenetic background.

Accurate identification of micro-RNAs that contribute significantly to a particular pathway (such as EMT) within breast cancers in situ is one hurdle. MicroRNAs have hundreds of potential targets, and in vivo studies will be needed to identify physiologically important targets in the context of breast cancer, as well as to develop effective treatments for breast cancer that involve manipulating microRNA expression levels and identifying off-target effects. (Adams et al.,2007;Zhao et al.,2008;Leva et al.,2010;Stinson et al.,2011;Acunzo et al.,2011;Castellano et al.,2009).

Domain of Applicability

A free-text section of the KER description that the developers can use to explain their rationale for the taxonomic, life stage, or sex applicability structured terms. More help

Humans and animals with no specific gender or life stage specificity.


List of the literature that was cited for this KER description. More help

Acunzo, M., Visone, R., Romano, G., Veronese, A., Lovat, F., Palmieri, D., ... & Croce, C. M. (2012). miR-130a targets MET and induces TRAIL-sensitivity in NSCLC by downregulating miR-221 and 222. Oncogene31(5), 634-642.

Adams, B. D., Guttilla, I. K., & White, B. A. (2008, November). Involvement of microRNAs in breast cancer. In Seminars in reproductive medicine (Vol. 26, No. 06, pp. 522-536). © Thieme Medical Publishers.

Adams, B. D., Furneaux, H., & White, B. A. (2007). The micro-ribonucleic acid (miRNA) miR-206 targets the human estrogen receptor-α (ERα) and represses ERα messenger RNA and protein expression in breast cancer cell lines. Molecular endocrinology21(5), 1132-1147.

Al Saleh, S., Al Mulla, F., & Luqmani, Y. A. (2011). Estrogen receptor silencing induces epithelial to mesenchymal transition in human breast cancer cells. PloS one6(6), e20610.

Bernardo, G. M., Lozada, K. L., Miedler, J. D., Harburg, G., Hewitt, S. C., Mosley, J. D., ... & Keri, R. A. (2010). FOXA1 is an essential determinant of ERα expression and mammary ductal morphogenesis. Development137(12), 2045-2054.

Bouris, P., Skandalis, S. S., Piperigkou, Z., Afratis, N., Karamanou, K., Aletras, A. J., ... & Karamanos, N. K. (2015). Estrogen receptor alpha mediates epithelial to mesenchymal transition, expression of specific matrix effectors and functional properties of breast cancer cells. Matrix Biology43, 42-60.

Castellano, L., Giamas, G., Jacob, J., Coombes, R. C., Lucchesi, W., Thiruchelvam, P., ... & Stebbing, J. (2009). The estrogen receptor-α-induced microRNA signature regulates itself and its transcriptional response. Proceedings of the National Academy of Sciences106(37), 15732-15737.

Di Leva, G., Gasparini, P., Piovan, C., Ngankeu, A., Garofalo, M., Taccioli, C., ... & Croce, C. M. (2010). MicroRNA cluster 221-222 and estrogen receptor α interactions in breast cancer. JNCI: Journal of the National Cancer Institute102(10), 706-721.

Eeckhoute, J., Keeton, E. K., Lupien, M., Krum, S. A., Carroll, J. S., & Brown, M. (2007). Positive cross-regulatory loop ties GATA-3 to estrogen receptor α expression in breast cancer. Cancer research67(13), 6477-6483.

Ito, I., Hanyu, A., Wayama, M., Goto, N., Katsuno, Y., Kawasaki, S., ... & Yanagisawa, J. (2010). Estrogen inhibits transforming growth factor β signaling by promoting Smad2/3 degradation. Journal of biological chemistry285(19), 14747-14755.

Kouros-Mehr, H., Kim, J. W., Bechis, S. K., & Werb, Z. (2008). GATA-3 and the regulation of the mammary luminal cell fate. Current opinion in cell biology20(2), 164-170.

Lin, H. Y., Liang, Y. K., Dou, X. W., Chen, C. F., Wei, X. L., Zeng, D., ... & Zhang, G. J. (2018). Notch3 inhibits epithelial–mesenchymal transition in breast cancer via a novel mechanism, upregulation of GATA-3 expression. Oncogenesis7(8), 1-15.

Liu, Y., Liu, R., Fu, P., Du, F., Hong, Y., Yao, M., ... & Zheng, S. (2015). N1-Guanyl-1, 7-diaminoheptane sensitizes estrogen receptor negative breast cancer cells to doxorubicin by preventing epithelial-mesenchymal transition through inhibition of eukaryotic translation initiation factor 5A2 activation. Cellular Physiology and Biochemistry36(6), 2494-2503.

Nakshatri, H., & Badve, S. (2009). FOXA1 in breast cancer. Expert reviews in molecular medicine11.

Stinson, S., Lackner, M. R., Adai, A. T., Yu, N., Kim, H. J., O’Brien, C., ... & Dornan, D. (2011). TRPS1 targeting by miR-221/222 promotes the epithelial-to-mesenchymal transition in breast cancer. Science signaling4(177), ra41-ra41.

Taylor, M. A., Parvani, J. G., & Schiemann, W. P. (2010). The pathophysiology of epithelial-mesenchymal transition induced by transforming growth factor-β in normal and malignant mammary epithelial cells. Journal of mammary gland biology and neoplasia15(2), 169-190.

Wilson, B. J., & Giguère, V. (2008). Meta-analysis of human cancer microarrays reveals GATA3 is integral to the estrogen receptor alpha pathway. Molecular cancer7(1), 1-8.

Wik, E., Ræder, M. B., Krakstad, C., Trovik, J., Birkeland, E., Hoivik, E. A., ... & Salvesen, H. B. (2013). Lack of estrogen receptor-α is associated with epithelial–mesenchymal transition and PI3K alterations in endometrial carcinoma. Clinical Cancer Research19(5), 1094-1105.

Yan, W., Cao, Q. J., Arenas, R. B., Bentley, B., & Shao, R. (2010). GATA3 inhibits breast cancer metastasis through the reversal of epithelial-mesenchymal transition. Journal of Biological Chemistry285(18), 14042-14051.

Ye, Y., Xiao, Y., Wang, W., Yearsley, K., Gao, J. X., Shetuni, B., & Barsky, S. H. (2010). ERα signaling through slug regulates E-cadherin and EMT. Oncogene29(10), 1451-1462.

Zeng, Q., Zhang, P., Wu, Z., Xue, P., Lu, D., Ye, Z., ... & Yan, X. (2014). Quantitative proteomics reveals ER-α involvement in CD146-induced epithelial-mesenchymal transition in breast cancer cells. Journal of proteomics103, 153-169.

Zhao, J. J., Lin, J., Yang, H., Kong, W., He, L., Ma, X., ... & Cheng, J. Q. (2008). MicroRNA-221/222 negatively regulates estrogen receptorα and is associated with tamoxifen resistance in breast cancer. Journal of Biological Chemistry283(45), 31079-31087.