Our lab has previously reported the identification of a novel endogenous 19-nor steroid, estradienolone (ED), in pregnant women that strongly bound to sex hormone binding globulin. Estrogen-receptor related receptors (ERRs), which have no known natural ligands, are a family of orphan receptors consisting of 3 isoforms: ERRalpha, ERRbeta and ERRgamma. The ERRs have been shown to actively modulate estrogenic responses, to play an essential role in pregnancy, and are implicated in breast cancer prognosis. My results show that ED acts as an antagonist of the ERRalpha confirming preliminary results obtained by our group. Studies of cellular responses demonstrate that ED has strong anti-mitogenic properties. ED inhibited the growth of both estrogen receptor (ER)-positive (MCF-7) and ER-negative (MDA-MB-231) breast cancer cells in a dose-dependent manner but did not have any effects on the proliferation of the non-cancerous immortalized epithelial breast MCF-10A cells. The finding that ED inhibits proliferation of both ER negative and ER positive breast cancer cells, and regulate ERR transcriptional activity may have important ramifications in breast cancer therapy.

This thesis investigates estrogens' modulation of three aspects of social cognition (aggression and agonistic behaviour, social learning, and social recognition). Sex-typical agonistic behaviour (males: overt attacks, females: more subtle dominance behaviours) was increased in gonadectomized mice by estrogen receptor alpha (ERα) agonist 1,3,5-tris(4-hydroxyphenyl)-4-propyl-1H-pyrazole (PPT), while non-overt agonistic behaviour was increased in male and female gonadally intact mice by ERβ agonist 7-Bromo-2-(4-hydroxyphenyl)-1,3-benzoxazol-5-ol (WAY-200070). Estrogens also affected the social transmission of food preferences (STFP). Acute estrogen and ERβ agonists WAY-200070 and 2,3-bis(4-hydroxyphenyl)propionitrile (DPN) prolonged the preference for the demonstrated food when administered pre-acquisition, likely by affecting motivation or the nature of the social interaction, while acute PPT blocked the STFP. All mice receiving any of the three treatments chronically showed a prolonged demonstrated food preference, suggesting a loss of ER specificity. Individual differences in social recognition may relate to increased oxytocin (OT) and vasopressin (AVP) mRNA, and ERα and ERβ gene activation, in the medial preoptic area, and decreased mRNA for ERs, OT receptor (OTR), AVP and AVP receptors 1a and 1b in the lateral amygdala. Additionally, dorsolateral septum ERs, progesterone receptor, and OTR may relate to social interest without affecting social recognition. Our and others' results suggest that estrogens, OT and AVP are all involved in social behaviours and mediate social recognition, social learning, social interactions, and aggression. ERs differently modulate the two types of social learning investigated here: ERα is critical for social recognition, but impairs social learning, while ERβ is less important in social recognition, and prolongs the demonstrated food preference in the STFP. This may be due to differences in receptor brain distributions or in downstream neurochemical systems that mediate these behaviours. The results of this thesis suggest that estrogens, through the various systems they modulate, have a key role to play in social behaviour. Further investigations of how estrogens effect change in these systems at the molecular and cellular level, as well as the critical brain areas and downstream effectors involved in these complex behaviours, are needed, and could contribute to therapeutic interventions in socially-based, sexually dimorphic disorders, like the autism spectrum disorders, and women receiving hormone replacement therapy for negative peri- or post-menopausal symptoms. / National Science and Engineering Research Council (PGS-D, CGS-M)

Les œstrogènes, et en particulier l’œstradiol E2, régulent un nombre considérable de fonctions physiologiques au sein de l’organisme et permettent notamment l’établissement et le maintien des fonctions reproductives chez tous les vertébrés. L’E2 agit localement dans de multiples organes cibles via l’intermédiaire de ses récepteurs : ERα et ERβ. Par son action proliférative contribuant au renouvellement de l’épithélium mammaire, l’E2 ainsi que son récepteur ERα ont été associés au développement pathologique de tumeurs mammaires. Celles-ci sont qualifiées d’hormono-dépendantes car elles répondent pour la majorité d’entre elles à l’utilisation de l’hormonothérapie visant à bloquer leur croissance. Malheureusement, on estime que 30 à 40% des tumeurs mammaires finissent par présenter une résistance aux traitements anti-oestrogéniques, par des mécanismes extrêmement complexes. Les travaux présentés dans ce manuscrit ont pour objectifs de mieux comprendre les mécanismes moléculaires et cellulaires impliqués dans le phénomène d’échappement des cellules tumorales mammaires au contrôle hormonal. Dans le cadre de cette thèse, nous nous sommes intéressés à deux facteurs capables de moduler l’activité d’ERα : l’hypoxie, qui désigne l’appauvrissement en oxygène du microenvironnement cellulaire, et la voie RhoA/MKL1 fréquemment mise en place au cours de la transition épithélio-mésenchymateuse. L’hypoxie est une caractéristique majeure des tumeurs solides, et des études lui suggèrent un rôle dans l’apparition de résistance endocrine. Nous montrons que le stress hypoxique inhibe fortement l’expression d’ERα, principalement au niveau protéique, et qu’il abolit la prolifération et la survie cellulaire induites par l’E2. L’analyse transcriptomique démontre qu’un certain nombre de gènes cibles d’ERα sont également régulés par l’hypoxie, qui peut soit réprimer (CXCL12…) ou bien augmenter leur expression (AREG…). Par ailleurs, l’analyse du cistrome d’ERα démontre une perte massive du nombre d’ERBSs (Estrogen Receptor Binding Site) par l’hypoxie, mais également une apparition d’ERBSs hypoxie-spécifiques. Nos résultats suggèrent que le fort recouvrement de régulation entre ERα et l’hypoxie puisse moduler l’efficacité des thérapies antihormonales. Enfin, l’équipe a démontré que l’activation de la voie RhoA/MKL1 provoque une forte inhibition de la fonction AF1 d’ERα. Afin de mieux appréhender les effets de cette voie de signalisation sur l’activité d’ERα, une lignée cellulaire MCF7 exprimant stablement un mutant constitutivement actif du facteur MKL1 a été générée. Nous montrons que son expression modifie profondément le contexte cellulaire en provoquant le basculement d’un phénotype luminal vers un phénotype basal-like. L’analyse transcriptomique de la réponse à l’E2 montre que le changement d’orientation cellulaire induit par MKL1 abolit toute régulation transcriptionnelle des gènes cibles d’ERα. Ce changement d’orientation cellulaire s’accompagne d’une reprogrammation massive du cistrome d’ERα avec une perte importante de ses sites de fixation à la chromatine, mais également de façon inattendue, un enrichissement en nouveaux ERBSs. Enfin, nous montrons une forte augmentation des interactions « non-génomiques » d’ERα avec des partenaires cytoplasmiques tels que PI3K, MSK1 et Src. Ces données suggèrent que dans des cellules agressives de type mésenchymal exprimant ERα, l’activité du récepteur repose majoritairement sur son action « non-génomique ». De façon intéressante, l’utilisation de l’anti-œstrogène pur ICI 182 780 n’a aucun effet inhibiteur sur ces interactions, pour lesquelles un rôle fonctionnel reste à établir. / Estrogens, and in particular estradiol E2, regulate a considerable number of physiological functions in the body and allow the establishment and maintenance of reproductive functions in all vertebrates. E2 acts locally in multiple target organs via its receptors: ERα and ERβ. By its proliferative action contributing to the renewal of the mammary epithelium, E2 as well as its ERα receptor have been associated with the pathological development of mammary tumors. These are qualified as hormone-dependent because they, for the majority of them, respond to the use of hormone therapy to block their growth. Unfortunately, it is estimated that 30-40% of mammary tumors end up with resistance to anti-estrogen treatments, through extremely complex mechanisms. The work presented in this manuscript aims to better understand the molecular and cellular mechanisms involved in the escape of mammary tumor cells to hormonal control. In this thesis, we looked at two factors that can modulate the ERα activity: hypoxia, which refers to oxygen depletion in the cellular microenvironment, and the RhoA/MKL1 pathway that is frequently activated during the epithelial-mesenchymal transition. Hypoxia is a major feature of solid tumors, and studies suggest a role in the development of endocrine resistance in breast cancer. We show that hypoxic stress strongly inhibits the expression of ERα, mainly at the protein level, and that it abolishes E2-induced cell proliferation and survival. Transcriptomic analysis shows that a certain number of ERα target genes are also regulated by hypoxia, which can either repress (CXCL12) or increase their expression (AREG ...). Moreover, the analysis of the ERα cistrome demonstrates a massive loss of the number of ERBSs (Estrogen Receptor Binding Site) by hypoxia, but also an appearance of hypoxia-specific ERBSs. Our results suggest that the strong regulatory overlap between ERα and hypoxia may modulate the efficacy of anti-hormonal therapies. Finally, the team demonstrated that the activation of the RhoA/MKL1 pathway causes a strong inhibition of the ERα AF1 function. In order to better understand the effects of this signaling pathway on ERα activity, an MCF7 cell line stably expressing a constitutively active mutant of the MKL1 factor was generated. We show that its expression profoundly modifies the cellular context by causing the switch from a luminal phenotype to a basal-like phenotype. The transcriptomic analysis of the E2 response shows that the MKL1 induced change in cell fate abolishes any transcriptional regulation of ERα target genes. This change in cellular orientation is accompanied by massive reprogramming of the ERα cistrome with a significant loss of its chromatin binding sites, but also unexpectedly, an enrichment of new ERBSs. Finally, we show a strong increase of "non-genomic" ERα interactions with cytoplasmic partners such as PI3K, MSK1 and Src. These data suggest that in aggressive mesenchymal cells expressing ERα, the receptor activity is mainly based on its "non-genomic" action. Interestingly, the use of pure anti-estrogen ICI 182 780 has no inhibitory effect on these interactions, for which a functional role remains to be established.

Introdução: Estimativas mostram que mais de dois terços das mulheres com câncer de mama possuem receptores hormonais positivos, e recebem terapia endócrina como tratamento, sendo tamoxifeno (TAM) o tratamento padrão (EBCTCG 2005; Davies et al., 2012). Porém, muitas pacientes se tornam resistentes com o passar do tempo. Estudos prévios mostraram que a expressão do receptor de estrogênio β (REβ) aumenta a resposta ao tratamento com TAM em células de câncer de mama, assim como a coexpressão de REα e REβ esta associada com maior ação proliferativa de TAM (Treeck et al., 2010; Sun et al., 2014). Também foi observada a existência de “cross-talk” entre os RE e a família do receptor do fator de crescimento epidérmico (HER) na resposta ao tratamento com TAM (Lindberg et al., 2011; Blows et al., 2010). Objetivo: Verificar a expressão do REβ, e suas interações com REα e receptores HER, durante o tratamento com TAM e em células resistentes ao TAM. Métodos: A expressão do REβ foi analisada em dois bancos de dados contendo informações de pacientes com câncer de mama. A expressão de RNAm dos RE, receptores HER e vias de sinalização PTEN, Akt e MAPK foram avaliadas após tratamento com TAM, em células resistentes ao TAM e em células silenciadas para os genes dos RE. Também foi avaliada a viabilidade celular após tratamento com TAM e nas células silenciadas para os genes dos RE. Resultados: Pacientes com câncer de mama apresentaram expressão reduzida do REβ, e os subtipos de câncer de mama REα positivos apresentaram baixa expressão do REβ quando comparados aos subtipos REα negativos. Células expressando níveis moderados de REβ apresentaram melhor resposta ao tratamento com TAM. Diminuição nos níveis dos RE é acompanhada por aumento nos níveis dos receptores ErbB2 e ErbB3, aumento de PTEN e diminuição de Akt e MAPK3 após tratamento com TAM. ERβ modula a ação antiproliferativa do TAM através da via de MAPK3. Células resistentes ao TAM apresentaram baixos níveis dos RE e altos níveis dos receptores EGFR, ErbB3 e ErbB4. Conclusão: Estes resultados demonstram que o REβ, e suas interações com REα e receptores HER, possuem papel importante na resposta ao tratamento com TAM. / Introduction: Approximately two-thirds of all breast cancer patients overexpress hormonal receptors, and are treated with endocrine therapy, being tamoxifen (TAM) the standard treatment. However many of initial responders to TAM as first-line experience relapse. Several mechanisms have been proposed to explain the occurrence of acquired TAM resistance. Previous studies showed that estrogen receptor β (ERβ) expression is associated with better response to tamoxifen treatment, as the co-expression of ERα and ERβ is associated with TAM antiproliferative effects. Moreover, there is growing interest about the cross-talk between ERs and ErbB family in response to endocrine therapy. Suggesting that TAM can acts through ERβ and/or ErbB family as compensatory pathways. Objective: To evaluate the expression of ERβ and the relation of ERβ with ERα and ErbB family in response to TAM treatment and in TAM resistant cells. Methods: ERβ expression was analyzed in two different databases of breast cancer patients. The mRNA levels of ER, HER receptors and PTEN, Akt and MAPK signal pathways were measured after TAM treatment, in TAM resistance cells and in cells silenced for ER genes. The cellular viability was also measured after TAM treatment, in TAM resistance cells and in cells silenced for ER genes. Results: Breast cancer patients presented reduced ERβ expression and the ERα-positive breast cancer subtypes presented lower ERβ levels when compared to ERα-negative breast cancer subtypes. Cells expressing moderates levels of ERβ presented better response to TAM treatment. Down-regulation of ERs induced by TAM treatment are accompanied with an increase in ErbB2 and ErbB3, reduced AKT and MAPK3 mRNA levels and increased PTEN levels. ERβ modulates TAM anti-proliferative effects through MAPK3 pathway. TAM– resistant cells expressed decreased ER mRNA levels and increased EGFR, ErbB3 and ErbB4 levels. Demonstrating that the cross-talk between ERs and HER family influence the response to TAM treatment. Conclusion: These results provide additional data indicating the importance of ERβ, and the relation with ERα and HER receptors, to predict TAM responsiveness.

Introdução: Estimativas mostram que mais de dois terços das mulheres com câncer de mama possuem receptores hormonais positivos, e recebem terapia endócrina como tratamento, sendo tamoxifeno (TAM) o tratamento padrão (EBCTCG 2005; Davies et al., 2012). Porém, muitas pacientes se tornam resistentes com o passar do tempo. Estudos prévios mostraram que a expressão do receptor de estrogênio β (REβ) aumenta a resposta ao tratamento com TAM em células de câncer de mama, assim como a coexpressão de REα e REβ esta associada com maior ação proliferativa de TAM (Treeck et al., 2010; Sun et al., 2014). Também foi observada a existência de “cross-talk” entre os RE e a família do receptor do fator de crescimento epidérmico (HER) na resposta ao tratamento com TAM (Lindberg et al., 2011; Blows et al., 2010). Objetivo: Verificar a expressão do REβ, e suas interações com REα e receptores HER, durante o tratamento com TAM e em células resistentes ao TAM. Métodos: A expressão do REβ foi analisada em dois bancos de dados contendo informações de pacientes com câncer de mama. A expressão de RNAm dos RE, receptores HER e vias de sinalização PTEN, Akt e MAPK foram avaliadas após tratamento com TAM, em células resistentes ao TAM e em células silenciadas para os genes dos RE. Também foi avaliada a viabilidade celular após tratamento com TAM e nas células silenciadas para os genes dos RE. Resultados: Pacientes com câncer de mama apresentaram expressão reduzida do REβ, e os subtipos de câncer de mama REα positivos apresentaram baixa expressão do REβ quando comparados aos subtipos REα negativos. Células expressando níveis moderados de REβ apresentaram melhor resposta ao tratamento com TAM. Diminuição nos níveis dos RE é acompanhada por aumento nos níveis dos receptores ErbB2 e ErbB3, aumento de PTEN e diminuição de Akt e MAPK3 após tratamento com TAM. ERβ modula a ação antiproliferativa do TAM através da via de MAPK3. Células resistentes ao TAM apresentaram baixos níveis dos RE e altos níveis dos receptores EGFR, ErbB3 e ErbB4. Conclusão: Estes resultados demonstram que o REβ, e suas interações com REα e receptores HER, possuem papel importante na resposta ao tratamento com TAM. / Introduction: Approximately two-thirds of all breast cancer patients overexpress hormonal receptors, and are treated with endocrine therapy, being tamoxifen (TAM) the standard treatment. However many of initial responders to TAM as first-line experience relapse. Several mechanisms have been proposed to explain the occurrence of acquired TAM resistance. Previous studies showed that estrogen receptor β (ERβ) expression is associated with better response to tamoxifen treatment, as the co-expression of ERα and ERβ is associated with TAM antiproliferative effects. Moreover, there is growing interest about the cross-talk between ERs and ErbB family in response to endocrine therapy. Suggesting that TAM can acts through ERβ and/or ErbB family as compensatory pathways. Objective: To evaluate the expression of ERβ and the relation of ERβ with ERα and ErbB family in response to TAM treatment and in TAM resistant cells. Methods: ERβ expression was analyzed in two different databases of breast cancer patients. The mRNA levels of ER, HER receptors and PTEN, Akt and MAPK signal pathways were measured after TAM treatment, in TAM resistance cells and in cells silenced for ER genes. The cellular viability was also measured after TAM treatment, in TAM resistance cells and in cells silenced for ER genes. Results: Breast cancer patients presented reduced ERβ expression and the ERα-positive breast cancer subtypes presented lower ERβ levels when compared to ERα-negative breast cancer subtypes. Cells expressing moderates levels of ERβ presented better response to TAM treatment. Down-regulation of ERs induced by TAM treatment are accompanied with an increase in ErbB2 and ErbB3, reduced AKT and MAPK3 mRNA levels and increased PTEN levels. ERβ modulates TAM anti-proliferative effects through MAPK3 pathway. TAM– resistant cells expressed decreased ER mRNA levels and increased EGFR, ErbB3 and ErbB4 levels. Demonstrating that the cross-talk between ERs and HER family influence the response to TAM treatment. Conclusion: These results provide additional data indicating the importance of ERβ, and the relation with ERα and HER receptors, to predict TAM responsiveness.

Carvacrol is a phenol monoterpene found in aromatic plants specially in Lamiaceae family, which has been evaluated in an experimental model of breast cancer. However, any proposed mechanism based on its antitumor effect has not been reported. In our previous study, carvacrol showed a protective effect on 7,12-dimethylbenz[α]anthracene- (DMBA-) induced breast cancer in female rats. The main objective in this research was to evaluate by using in silico study the carvacrol on HER2, PI3Kα, mTOR, hERα, PR, and EGFR receptors involved in breast cancer progression by docking analysis, molecular dynamic, and drug-likeness evaluation. A multilevel computational study to evaluate the antitumor potential of carvacrol focusing on the main targets involved in the breast cancer was carried out. The in silico study starts with protein-ligand docking of carvacrol followed by ligand pathway calculations, molecular dynamic simulations, and molecular mechanics energies combined with the Poisson–Boltzmann (MM/PBSA) calculation of the free energy of binding for carvacrol. As result, the in silico study led to the identification of carvacrol with strong binding affinity on mTOR receptor. Additionally, in silico drug-likeness index for carvacrol showed a good predicted therapeutic profile of druggability. Our findings suggest that mTOR signaling pathway could be responsible for its preventive effect in the breast cancer. / Revisión por pares

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About 70% of breast tumors express the estrogen receptor alpha (ERα). Antiestrogens (AEs) are used to treat all stages of ER+ breast cancer. There are two types of AEs: Selective Estrogen Receptor Modulators (SERMs) and Selective Estrogen Receptor Downregulators (SERDs). SERMs such as Tamoxifen (Tam) have tissue-specific partial agonist activity, while SERDs such as Fulvestrant or Faslodex (ICI182, 780) fully repress estrogen target genes regardless of the tissue and cell type. Previously, it has been reported that SERDs induce ERα ubiquitination and degradation. ERα is also SUMOylated in the presence of SERDs. Abrogating SUMOylation of ERα using a deSUMOylase (SENP1) resulted in a partial de-repression of estrogen target genes in the presence of SERDs. Mapping the domains using deletion mutagenesis in the presence of ICI 182,780 showed that C-terminal domain (CDEF regions) is required of the ICI induced modification but not the N-terminal domain (AB region). Thus, a detailed dissection of the structural determinants for the selective action of SERDs on ERα SUMOylation and ubiquitination remained unknown. Our work shows that pure antiestrogens like ICI182,780 induce SUMOylation and ubiquitination of ERα but not ERβ in live cells. Utilizing the fact that domains of ERα and ERβ display sequence homology, we designed chimeras to map the minimal domain required for ERα modification in the presence of antiestrogens. Interestingly, swapping domains between ERα and ERβ showed that the Ligand Binding Domain (LBD) of ERα is sufficient to confer the induction of ERα modification in the presence of AEs such as Raloxifene (Ral) and ICI182,780. Further dissecting this region, we also found that helices 3 to 6 (H3H6) located in the LBD region is sufficient to confer the induction of SUMOylation and ubiquitination in the ICI182,780. Importantly, the lysine residues in this region between ERα and ERβ are conserved, which suggests that conformational differences in the LBD determine the capacity of ICI182, 780 bound ERα to be modified by SUMO and ubiquitin. Replacement of Leucine at position 536 in helix 12 (H12) of ERα’s LBD by a Valine residue or mutating Aspartate at position 351 abolished the increase in SUMOylation and ubiquitination observed in the presence of Ral. This suggested that Ral, a SERM, required a different set of determinants than ICI182,780 present in the LBD of ERα. vi Our work has also showed that saturating concentrations (increasing the amount of drug added will not result in a higher response) of ICI 182,780 modified and fully repressed constitutively active mutations such as Y537C, N or S and D538G. Other mutation such V534E and L536R/Q mutants exhibited some residual activity and were not modified in the presence of saturating concentrations of ICI182,780. Interestingly, the loss of SUMOylation correlated with the partial resistance to AEs. Structure function analysis of residues at position 536 indicates amino acids with a bulky hydrophobic side chain residue at this position result in preservation of ERα modifications in the presence of ICI 182,780. However, Using BRET-FECT, we have demonstrated that ERαwt/L536R heterodimerize and have intermediate levels of SUMOylation compared to ERαwt in the presence of ICI 182,780. Our results shed light onto the molecular basis for the diverse pharmacological properties of antiestrogens and should help guide the design of novel SERDs for breast cancer treatment. / Environ 70% des cancers du sein expriment le récepteur des oestrogènes alpha (ERα). Les anti-oestrogènes (AEs) sont utilisés pour traiter tous les stades de cancer du sein ER+. Il y a deux types d’AEs : les Selective ER Modulators (SERMs) et les Selective ER Downregulators (SERDs). Les SERMs, comme le Tamoxifen (Tam), ont une activité agoniste partielle tissu-spécifique, alors que les SERDs, tel Fulvestrant ou Faslodex (ICI182,780), répriment entièrement les gènes cibles d’ER, quel que soit l’organe ou le type cellulaire. Il a précédemment été montré que les SERDs induisent l’ubiquitination et la dégradation d’ERα. ERα est aussi SUMOylé en présence des SERDs. Supprimer la SUMOylation d’ERα en utilisant une déSUMOylase (SENP1) résulte en une dérépression partielle des gènes cibles d’ER en présence de SERDs. La délétion successive des différents domaines d’ERα en présence d’ICI182,780 a révélé que la région C-terminale (domaines CDEF) est requise pour la modification induite par ICI, mais pas la région N-terminale (domaines AB). Ainsi, la dissection détaillée des déterminants structuraux responsables de l’activité sélective des SERDs pour la SUMOylation et l’ubiquitination d’ERα reste à entreprendre. Nos travaux montrent que les AEs purs comme ICI182,780 induisent la SUMOylation d’ERα, mais pas d’ERβ, dans des cellules en culture. Tirant profit de l’homologie de séquences des différents domaines d’ERα et ERβ, nous avons conçu des chimères pour cartographier la région minimale requise pour la modification d’ERα en présence d’AEs. De manière intéressante, l’interversion des domaines d’ERα et ERβ a montré que le domaine de liaison au ligand (LBD) d’ERα est suffisant pour permettre l’induction de la modification d’ERα en présence d’AEs tels le Raloxifene (Ral) et ICI182,780. En décortiquant davantage ce domaine, nous avons trouvé que les hélices 3 à 6 (H3H6) du LBD sont suffisantes pour induire la SUMOylation et l’ubiquitination d’ERα en présence d’ICI182,780. De manière importante, les résidus Lysine de cette région sont conservées entre ERα et ERβ, ce qui suggère que des différences conformationnelles entre les deux LBD déterminent la capacité d’ERα lié par ICI182,780 d’être modifié par SUMO et l’ubiquitine. La mutation de la Leucine à la position 536 dans l’hélice H12 du LBD d’ERα par une Valine, ou la mutation de l’Aspartate à la position 351 abolissent l’augmentation de la SUMOylation et l’ubiquitination observée en présence de iv Ral. Cela suggère que Ral, un SERM, requière différents déterminants structuraux du LBD d’ERα qu’ICI182,780. Nos travaux ont aussi montré que des concentrations saturantes (l’augmentation de la quantité de drogue ajoutée ne mènera pas à une réponse plus élevée) d’ICI182,780 modifient et répriment entièrement des mutants constitutivement actifs d’ERα comme Y537C, N ou S et D538G. D’autres mutants, tels V534E et L536R/Q, présentent une activité résiduelle et ne sont pas modifiés sous traitement avec des concentrations saturantes d’ICI182,780. De façon intéressante, la perte de SUMOylation corrèle avec la résistance partielle aux AEs. Une analyse structure – fonction des résidus à la position 536 indique que les acides aminés avec une chaine latérale hydrophobe volumineuse à cette position permettent de préserver les modifications d’ERα en présence d’ICI182,780. Cependant, en utilisant la technique BRET-FECT, nous avons démontré que les récepteurs ERα sauvage et L536R forment un hétérodimère qui présente des niveaux intermédiaires de SUMOylation en présence d’ICI182,780. Nos résultats révèlent les bases moléculaires des diverses propriétés pharmacologiques des AEs et devraient aider à guider la conception de nouveaux SERDs pour le traitement des cancers du sein.

No description available.