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Simple Summary The alteration of mismatch repair (MMR) genes leads to microsatellite instability and plays a key role in colorectal cancer (CRC) pathogenesis and prognosis. The transcription factor NRIP1 is involved in intestinal tumorigenesis and is a good prognostic marker in CRC. In this study, we demonstrate that NRIP1 induces MSH2 and MSH6 MMR gene transcription and reduces microsatellite instability. A dominant-negative truncated NRIP1 mutant amplifies the MMR-deficient phenotype and appears as a key player in MSI-driven tumorigenesis since it significantly correlates with a short overall survival of patients with advanced CRC, especially MLH1-deficient ones. Abstract Microsatellite instability (MSI) is related to the alteration of mismatch repair (MMR) genes and plays a key role in colorectal cancer (CRC) pathogenesis. We previously reported that the transcription factor Nuclear Receptor Interacting Protein 1 (NRIP1) is involved in sporadic intestinal tumorigenesis. The aim of this study was to decipher its role in MSI CRC. By using different mouse models and engineered cell lines, we demonstrated that NRIP1 increased MSH2 and MSH6 MMR gene transcription and mRNA/protein levels. In human CRC cells, NRIP1 expression was associated with decreased MSI and the hypermutator phenotype, and with resistance to chemotherapy drugs. Using a cohort of 194 CRC patients, we detected in 22% of the cases a MSI-induced frameshift mutation in the NRIP1 coding sequence. This genetic alteration generates a truncated protein with a dominant negative activity that increased human CRC cell proliferation and impaired the regulation of MSH2 and MSH6 gene expression. Moreover, the NRIP1 mutant correlated with a decreased overall survival of patients with advanced CRC, especially when MLH1-deficient. By decreasing the expression of MSH2 and MSH6 gene expression, the NRIP1 variant may amplify MLH1-dependent CRC progression and behave as a new prognostic marker of advanced MSI CRC.

Le récepteur humain Pregnane X Receptor (hPXR, NR1I2) est impliqué dans la biosynthèse, la distribution et le métabolisme de stéroïdes, d’acides biliaires et de xénobiotiques, parmi lesquels de nombreux pesticides. Quand des xénobiotiques se lient au hPXR, ce complexe forme un hétérodimère avec le récepteur X des rétinoïdes (RXR) et induit l’expression de gènes de détoxication comme les gènes codant pour les enzymes de phase I (CYP), de phase II (conjugaison) ou des protéines de transport (transporteurs de la famille ABC), résultant en une clairance des stéroïdes, des drogues et xénobiotiques par le foie et l’intestin (Timsit et al, 2007). L’activation de hPXR a été associée à des interactions médicamenteuses, la perturbation endocrinienne, la chimiorésistance, la croissance et l’agressivité de cancers du côlon et du foie (Planque et al, 2016 ; Wang et al, 2011 ; Kodama et al, 2015 ; Pondugula et al, 2016). Des études récentes ont révélé l’activité hPXR d’échantillons environnementaux de milieux aquatiques comme les effluents urbains et industriels, les eaux de surface et les sédiments de rivière (Creusot et al, 2011 ; Dagnino et al, 2012). Comparativement au PXR humain, il apparaît que le PXR de poisson zèbre (zfPXR) est activé par un plus faible nombre de pesticides (Ekins et al, 2008 ; Krasowski et al, 2011 ; Milnes et al, 2008) et que certains d’entre eux ont une meilleure affinité pour zfPXR que pour hPXR, suggérant d’importantes différences entre les deux récepteurs. De plus, les rôles du PXR dans le métabolisme du poisson ne sont pas encore pleinement élucidés. Dans ce contexte, nous avons cherché à caractériser les interactions entre les pesticides et le PXR chez l'homme et le poisson zèbre et à étudier le rôle de zfPXR dans le métabolisme du poisson. À cette fin, nous avons testé l'activité PXR d'échantillons environnementaux et de pesticides à l'aide de lignées cellulaires luminescentes exprimant soit hPXR soit zfPXR. Les pesticides les plus puissants ont ensuite été testés pour leur capacité à réguler l'expression des gènes cibles de PXR et à agir sur la prolifération cellulaire et la résistance aux médicaments dans ces cellules. Ces travaux seront combinés à des approches de modélisation (zfPXR) et de cristallographie (hPXR) pour étudier les interactions structurelles des pesticides avec hPXR et zfPXR, et à une approche in vivo utilisant le poisson zèbre pour étudier les effets des pesticides sur les gènes régulés par PXR. Dans l'ensemble, nos données permettent de mieux comprendre le rôle et les mécanismes d'action du PXR chez l'homme et le poisson zèbre et mettent en évidence des différences inter-espèces pour une meilleure évaluation des risques d'exposition aux pesticides pour la santé humaine et l'environnement.

International audience; Estrogens play a pivotal role in breast cancer etiology, and endocrine therapy remains the main first line treatment for estrogen receptor‐alpha (ER α)‐positive breast cancer. ER are transcription factors whose activity is finely regulated by various regulatory complexes, including histone deacetylases (HDACs). Here, we investigated the role of HDAC 9 in ER α signaling and response to antiestrogens in breast cancer cells. Various Michigan Cancer Foundation‐7 (MCF 7) breast cancer cell lines that overexpress class II a HDAC 9 or that are resistant to the partial antiestrogen 4‐hydroxy‐tamoxifen (OHTam) were used to study phenotypic changes in response to ER ligands by using transcriptomic and gene set enrichment analyses. Kaplan–Meier survival analyses were performed using public transcriptomic datasets from human breast cancer biopsies. In MCF 7 breast cancer cells, HDAC 9 decreased ER α mRNA and protein expression and inhibited its transcriptional activity. Conversely, HDAC 9 mRNA was strongly overexpressed in OHT am‐resistant MCF 7 cells and in ER α‐negative breast tumor cell lines. Moreover, HDAC 9‐overexpressing cells were less sensitive to OHT am antiproliferative effects compared with parental MCF 7 cells. Several genes (including MUC 1, SMC 3 and S100P) were similarly deregulated in OHT am‐resistant and in HDAC 9‐overexpressing MCF 7 cells. Finally, HDAC 9 expression was positively associated with genes upregulated in endocrine therapy‐resistant breast cancers and high HDAC 9 levels were associated with worse prognosis in patients treated with OHT am. These results demonstrate the complex interactions of class II a HDAC 9 with ER α signaling in breast cancer cells and its effect on the response to hormone therapy

As compared to (xeno-)estrogens, natural and synthetic ligands of the progesterone receptor (PR) have been scarcely studied on aquatic organisms while the potential risk posed by environmental progestins has been recently pointed out. However, there is still a lack of data to accurately characterize the hazards posed by these compounds. In that respect, the capacity of synthetic progestins to interact with fish nuclear progesterone receptor was poorly investigated. In the present work we aimed at assessing potential endocrine disruption of these compounds towards zebrafish nPR and to compare their effects with that of human nPR to identify possible interspecies differences. Two human cell lines co-expressing either human PR (hPR) or the zebrafish PR (ZfPR) and luciferase gene, namely HELN-hPRB and U2OS-zfPR cells, were developed and characterized using promegestone (R5020) as a reference agonist ligand. R5020 induced luciferase activity in both cell lines in a concentration-dependent manner. These effects were completely blocked by co-exposing the cells with mifepristone (RU486), a potent PR antagonist. A large set of natural and synthetic progestins (25) was screened in the two cell lines. All of the compounds except the natural zebrafish progestin 17α,20β-dihydroxy-4-pregnen-3-one (DHP) activated the hPR. About half of the progestins induced a maximum effect of 100% when compared to R5020 while the other half partially induced luciferase activity. In contrast to cells expressing hPR, progestins behaved very differently with the zfPR since only five of them were active on zfPR. Interestingly, we found that DHP strongly activated zfPR but not hPR. To assess whether some progestins were partial agonists, they were coexposed with R5020. Half of them antagonized the activity induced by R5020 on hPR and are thus partial hPR agonists. All the active progestins on zfPR antagonized R5020 and are therefore partial zfPR agonists. Two new luciferase reporter cell lines were developed and characterized, providing novel information regarding the activity of a large set of progestins on the zfPR. These models allowed us to highlight major interspecies differences. These results support the need to further determine the effects of zfPR agonist progestins on PR-dependent physiological processes in order to characterize the hazards posed by progestins in fish.

International audience; Endocrine-disrupting chemicals (EDCs) are exogenous substances interfering with hormone biosynthesis, metabolism, or action, and consequently causing disturbances in the endocrine system. Various pathways are activated by EDCs, including interactions with nuclear receptors (NRs), which are primary targets of numerous environmental contaminants. The main NRs targeted by environmental contaminants are the estrogen (ER α, β) and the androgen (AR) receptors. ERs and AR have pleiotropic regulatory roles in a diverse range of tissues, notably in the mammary gland, the uterus, and the prostate. Thus, dysfunctional ERs and AR signaling due to inappropriate exposure to environmental pollutants may lead to hormonal cancers and infertility. The pregnane X receptor (PXR) is also recognized by many environmental molecules. PXR has a protective role of the body through its ability to regulate proteins involved in the metabolism, the conjugation, and the transport of many exogenous and endogenous compounds. However, the permanent activation of this receptor by xenobiotics may lead to premature drug metabolism, the formation, and accumulation of toxic metabolites and defects in hormones homeostasis. The activity of other NRs can also be affected by environmental molecules. Compounds capable of inhibiting or activating the estrogen related (ERRγ), the thyroid hormone (TRα, β), the retinoid X receptors (RXRα, β, γ), and peroxisome proliferator-activated (PPAR α, γ) receptors have been identified and are highly suspected to promote developmental, reproductive, neurological, or metabolic diseases in humans and wildlife. In this review, we provide an overview of reporter cell lines established to characterize the human NR activities of a large panel of EDCs including natural as well as industrial compounds such as pesticides, plasticizers, surfactants, flame retardants, and cosmetics.

International audience; Zebrafish is increasingly used as an animal model to study the effects of environmental nuclear receptors (NRs) ligands. As most of these compounds have only been tested on human NRs, it is necessary to measure their effects on zebrafish NRs. Estrogen receptors (ER) α and β and peroxysome proliferator activated receptor (PPAR) γ are main targets of environmental disrupting compounds (EDCs). In humans there are two distinct nuclear ERs (hERα and hERβ), whereas the zebrafish genome encodes three ERs, zfERα, zfERβ1, and zfERβ2. Only one isoform of PPARγ is expressed in both humans and zebrafish. In this review, we described reporter cell lines that we established to study the interaction of EDCs with human and zebrafish ERs and PPARγ. Using these cell lines, we observed that zfERs are thermo-sensitive while zfPPARγ is not. We also showed significant differences in the ability of environmental and synthetic ligands to modulate activation of zfERs and zfPPARγ in comparison to hERs and hPPARγ. Some environmental estrogens (bisphenol A, mycoestrogens) which are hER panagonists displayed greater potency for zfERα as compared to zfERβs. hERβ selective agonists (8βVE2, DPN, phytoestrogens) also displayed zfERα selectivity. Among hERα selective synthetic agonists, 16α-LE2 was the most zfERα selective compound. Almost all zfPPARγ environmental ligands (halogenated bisphenol A derivatives, phthalates, perfluorinated compounds) displayed similar affinity for human and zebrafish PPARγ while pharmaceutical hPPARγ agonists like thiazolidones are not recognized by zfPPARγ. Altogether, our studies show that all hERs and hPPARγ ligands do not control in a similar manner the transcriptional activity of zfERs and zfPPARγ and point out that care has to be taken in transposing the results obtained using the zebrafish as a model for human physiopathology.

International audience

International audience; Vitamin B6 is well-known for its role as a cofactor in many enzymatic reactions and recently, several epidemiological studies have highlighted the importance of this vitamin as a protective agent against various cancers: elevated vitamin B6 plasma levels were associated with a lower risk of colorectal cancer development, for example. In vivo studies have shown that vitamin B6 decreased cell proliferation and enhanced the immune response. At the cellular level, antioxidant, pro-apoptotic and anti-angiogenic effects have been identified. At the molecular level, vitamin B6 is able to inhibit the transactivation potential of various nuclear receptors. Interestingly, a recent paper has described the conjugation of vitamin B6 to RIP140 (receptor interacting protein of 140 kDa), a protein that acts as a transcriptional corepressor of nuclear receptors. This post-translational modification increases the transcriptional repression of RIP140 and regulates its subcellular localization and its ability to interact with different protein partners. Finally, vitamin B6 is involved in the methyl donor cycle ant thus, some of the antitumor properties of vitamin B6 may involve an indirect effect on the level of DNA or histone methylation. All of these mechanistic and clinical data justify further studies to decipher the mechanism of action of vitamin B6 and its clinical interest in combination with molecules typically used in chemotherapy or hormonal therapy.

International audience; Background: The occurrence of halogenated analogs of the xenoestrogen bisphenol A (BPA) has been recently demonstrated both in environmental and human samples. These analogs include brominated [e.g., tetrabromobisphenol A (TBBPA)] and chlorinated [e.g., tetrachlorobisphenol A (TCBPA)] bisphenols, which are both flame retardants. Because of their structural homology with BPA, such chemicals are candidate endocrine disruptors. However, their possible target(s) within the nuclear hormone receptor superfamily has remained unknown.Objectives: We investigated whether BPA and its halogenated analogs could be ligands of estrogen receptors (ERs) and peroxisome proliferator–activated receptors (PPARs) and act as endocrine-disrupting chemicals.Methods: We studied the activity of compounds using reporter cell lines expressing ERs and PPARs. We measured the binding affinities to PPARγ by competitive binding assays with [3H]‑rosiglitazone and investigated the impact of TBBPA and TCBPA on adipocyte differentiation using NIH3T3-L1 cells. Finally, we determined the binding mode of halogenated BPAs to PPARγ by X‑ray crystallography.Results: We observed that TBBPA and TCBPA are human, zebrafish, and Xenopus PPARγ ligands and determined the mechanism by which these chemicals bind to and activate PPARγ. We also found evidence that activation of ERα, ERβ, and PPARγ depends on the degree of halogenation in BPA analogs. We observed that the bulkier brominated BPA analogs, the greater their capability to activate PPARγ and the weaker their estrogenic potential.Conclusions: Our results strongly suggest that polyhalogenated bisphenols could function as obesogens by acting as agonists to disrupt physiological functions regulated by human or animal PPARγ.