Le mitotane, ou o,p’DDD, médicament historique dérivé d’un insecticide, reste le traitement de référence du corticosurrénalome (CS), tumeur rare et de mauvais pronostic. Le mitotane exerce un effet anti-sécrétoire associé à un effet anti-tumoral dont les mécanismes d’action sous-jacents sont mal compris et ses cibles moléculaires restent inconnues. Néanmoins, de nombreux arguments semblent désigner la mitochondrie comme organite cible du mitotane. Dans ce travail de thèse, nous nous sommes intéressés à l’impact mitochondrial du mitotane par des approches complémentaires sur plusieurs modèles expérimentaux. Nous avons ainsi pu mettre en évidence une inhibition sélective des complexes I et IV de la chaîne respiratoire, une fission du réseau mitochondrial ou encore une activation de la biogenèse mitochondriale. Ces données nous ont permis d’identifier les mitochondrial-associated membranes (MAM) et le transducéosome comme organites cibles du mitotane. Parallèlement, en réévaluant le rôle potentiel du métabolite acide o,p’DDA, nous avons pu exclure son implication dans l’action cytotoxique du mitotane. Nous avons également démontré que le mitotane libre, non lié aux lipoprotéines, était le plus actif in vitro et pouvait ainsi être celui responsable de l’action pharmacologique in vivo. L’ensemble de ces résultats apportent une meilleure compréhension des mécanismes d’action du mitotane et devrait permettre d’identifier des facteurs prédictifs de réponse à ce traitement pour une meilleure prise en charge des patients atteints de CS. / Mitotane is o,p’DDD, an historic drug derived from an insecticide and represents the treatment of choice for adrenocortical carcinoma (ACC), a rare adrenal tumor associated with bad prognosis. Mitotane is responsible for an inhibition of steroidogenesis associated with an antitumoral effect but its exact molecular mechanisms of action remain unclear and its molecular target remains unknown. However, mitochondria could be an organite targeted by mitotane. In this study we evaluated mitochondrial impact of mitotane using complementary approaches on several experimental models. We showed a mitotane-induced selective inhibition of respiratory chain complexes I and IV, an increased fission of the mitochondrial network and an activation of the mitochondrial biogenesis. These data helped us to identify mitochondrial-associated membranes (MAM) and so-called transduceosome as targeted organites of mitotane. We also reevaluated the potential role of the acid metabolite o,p’DDA and excluded its implication in the cytotoxic action of mitotane. Finally, we demonstrated that free mitotane which is not linked to lipoproteins is more efficient in vitro and could be therefore responsible for pharmacological action in vivo. Altogether, these results allow to better understand mitotane mechanisms of action and should help to identify predictive markers of response to mitotane for a better care of patients with ACC.

O carcinoma adrenocortical (ACC) é um tumor maligno raro. O objetivo foi testar a ação de drogas antitumorais na linhagem H295R, em cultura 2D e 3D, analisadas por MTS, ensaios multiparamétricos, e microscopia confocal. Em monocamada (2D), as drogas tiveram maior efeito quando utilizadas com o mitotano 10 mM, sendo: everolimus 10 mM (50±0,02% p &#8804 0.001), imatinib (10 mM 52±0.01% p &#8804 0.001), sunitinib 5 mM (47±0.02% p &#8804 0.001), e nilotinib 5 mM (59±0,03% p &#8804 0.001), com evidência de apoptose. Nos esferoides (3D) foi necessário mitotano 30 M com everolimus 10 mM para se obter diminuição de 32±0.02% p &#8804 0.001 na viabilidade das células, e com nilotinib 10 mM para redução de 57±0.03% p &#8804 0.001, com evidência de necrose e apoptose. Em resumo, os dados sugerem que os esferoides são mais resistentes aos tratamentos, como ocorre com tumores in vivo, e podem representar uma importante abordagem para estudos de ACC. O nilotinib foi o que induziu as melhores respostas, tanto no modelo em 2D quanto 3D, resultados que se apresentam promissores para o tratamento dos carcinomas adrenocorticais. / Adrenocortical carcinoma (ACC) is a rare malignant tumor. The objective was to test the antitumor drugs action in the H295R cell line, in 2D and 3D culture system, by using MTS, multiparameter assay (High Content Screening) and confocal microscopy. In monolayer, all drugs were more effective in combination with mitotane 10 mM: everolimus 10 mM (50±0.02%), 10 mM imatinib (52±0.01%), 5 mM sunitinib (47±0.02%), and 5 mM nilotinib (59±0.03%). The spheroids required mitotano 30 mM with everolimus 10 mM to decrease cell viability (32±0.02% p &#8804 0.001); and with 10 mM nilotinib to inhibit cell viability in 57±0.03% (p &#8804 0.001), with induction of apoptosis and necrosis. In summary, the spheroids were more resistant to treatment and may represent an important approach for studies of ACC. Nilotinib was the tyrosine kinase inhibitor that, either alone or in combination with mitotane, induced higher cytotoxicity, in both 2D and 3D cell cultures, showing promising results for the treatment of adrenocortical carcinoma, as well as for the studies of its mechanism of action.

Les tumeurs corticosurrénaliennes unilatérales sont fréquentes (prévalence de 2 à 9% de la population). Il s’agit le plus souvent d’adénomes. Le cancer de la corticosurrénale, ou corticosurrénalome, a un pronostic sombre, la survie ne dépassant pas 40 % à cinq ans. Le diagnostic de malignité de ces tumeurs, actuellement basé sur l’histologie, peut être difficile. Le pronostic des corticosurrénalomes est hétérogène et peu prévisible. Enfin, la prise en charge thérapeutique est encore limitée. Ces difficultés diagnostiques, pronostiques et thérapeutiques s’expliquent entre autres par la connaissance limitée de la physiopathologie de ce cancer. Le génome a un rôle central dans le développement des cancers en général. La survenue d’altérations génomiques (mutations, anomalies de nombre de copies, pertes d’hétérozygotie, translocations, anomalies de méthylation) va aboutir à la surexpression d’oncogènes et à la répression de gènes suppresseurs de tumeurs. La génomique, en ouvrant la voie à la caractérisation moléculaire à l’échelle du génome entier des tumeurs, est devenue incontournable pour étudier la physiopathologie des cancers. Les études de transcriptome des tumeurs corticosurrénaliennes ont montré que le profil d’expression génique discrimine adénomes et corticosurrénalomes, et identifie deux groupes distincts de corticosurrénalomes avec des pronostics différents. Dans le sillage de ces travaux précédemment réalisés par l’équipe, je me suis intéressée pendant ma thèse aux anomalies de nombres de copies d'ADN et aux anomalies de méthylation des corticosurrénalomes. Dans une première partie j’ai étudié le génome de 38 adénomes et 21 corticosurrénalomes par puce d’hybridation génomique comparative (puces CGH). Le transcriptome de 54 de ces tumeurs était déjà disponible. Le génome des corticosurrénalomes est très altéré contrairement à celui des adénomes (44% du génome est perdu ou gagné, versus 10% pour les adénomes, p=2.10-10). Dans les adénomes, la région 9q34 (locus de SF-1) est fréquemment gagnée et ce gain est associé à une surexpression de SF-1. Pour les corticosurrénalomes, les évènements récurrents concernent les gains des chromosomes 5, 7, 12, 16, 19, 20 et les pertes des chromosomes 13 et 22. Les gènes situés dans les régions minimales communes gagnées ou perdues ont été filtrés en fonction de leur expression. La liste des gènes à la fois gagnés et surexprimés inclut des oncogènes comme FGFR4, CDK4, CCNE1 ; et la liste des gènes avec perte de matériel et sous-expression inclut des gènes suppresseurs de tumeurs (LATS2, ST13). Un outil diagnostique basé sur la mesure en PCR quantitative de 6 loci permet de séparer les corticosurrénalomes des adénomes dans une cohorte de validation indépendante de 79 tumeurs, avec une sensibilité de 100% et une spécificité de 83%. Le nombre d’altérations chromosomiques n’a pas de valeur pronostique, mais une technique de classification hiérarchique non supervisée permet de séparer les corticosurrénalomes en deux groupes de pronostic différent, et a été validée sur une cohorte indépendante de 25 tumeurs. Dans une deuxième partie, j’ai étudié les anomalies de méthylation des promoteurs des gènes de 51 corticosurrénalomes et 81 adénomes par puce Infinium HumanMethylation27 (Illumina). Les données d’expression étaient disponibles pour 87 tumeurs. Les corticosurrénalomes sont globalement hyperméthylés par rapport aux adénomes. La classification hiérarchique non supervisée sépare les corticosurrénalomes en 3 groupes : un groupe non-hyperméthylé, un groupe modérément hyperméthylé, et un autre très hyperméthylé. Cette classification a été confirmée par MS-MLPA. L’hyperméthylation est associée à un mauvais pronostic (p=0,02 en modèle de Cox). La corrélation entre niveau de méthylation et expression identifie 1741 gènes (sur les 12250 étudiés) corrélés négativement (…) / Unilateral adrenocortical tumors are common (prevalence : 2 to 9% of the population). Most of these tumors are adenomas. Adrenocortical cancer (ACC) has a poor prognosis, with a 5-yr survival rate not exceeding 40% in most series. Pathological diagnosis of these tumors relies on several histological features and can be difficult. The prognosis of adrenocortical carcinomas is heterogeneous and unpredictable. Knowledge of the pathophysiology of these tumors is also limited. The genome has a central role in the development of cancers in general. The occurrence of genomic alterations (mutations, abnormal copy number, loss of heterozygosity, translocations, abnormal methylation) will lead to the overexpression of oncogenes and repression of tumor suppressor genes. Genomic approaches became essential to study the pathophysiology of cancer. Transcriptome studies of adrenocortical tumors have shown that the gene expression profile discriminate ACC and adenomas, and identified two distinct groups of ACC with different prognoses. In addition to gene expression, genomics now covers a large spectrum of alterations, including chromosomal alterations, DNA sequence modifications, and epigenetic alterations. I studied chromosomal alterations and DNA methylation abnormalities in ACC during my thesis.In the first part the genome of 38 adrenocortical adenomas and 21 ACC were identified by comparative genomic hybridization arrays. The transcriptome of 54 of these tumors was already available. A larger proportion of the genome is altered in carcinomas compared with adenomas (44 % of the genome is lost or gained, versus 10% for adenomas , p = 2.10-10 ) . In adenomas, the 9q34 region, which includes the steroidogenic factor 1locus, is commonly gained and associated with an overexpression of steroidogenic factor 1 (SF-1).In carcinomas, recurrent gains include chromosomes 5, 7, 12, 16, 19, and 20 and recurrent losses chromosomes 13 and 22. Filtering the genes from these regions according to their expression profile identified genes potentially relevant to adrenocortical tumorigenesis. A diagnostic tool was built by combining DNA copy number estimates at six loci (5q, 7p, 11p, 13q, 16q, and 22q). This tool discriminates carcinomas from adenomas in an independent validation cohort (sensitivity 100%, specificity 83%). In carcinomas, the number of chromosomal alterations was not associated with survival (Cox p=0.84). A prognostic tool based on tumor DNA was designed with a clustering strategy and validated in an independent cohort. In the second part, methylation patterns of CpG islands in promoter regions of 51 adrenocortical carcinomas and 84 adenomas were studied by the Infinium HumanMethylation27 Beadchip (Illumina) . Gene expression data were available for 87 tumors. Methylation was higher in carcinomas than in adenomas (t test : p=3.1x10-9). Unsupervised clustering of DNA methylation profiles identified two groups of carcinomas, one with an elevated methylation level, evoking a CpG island methylator phenotype (CIMP). The subgroup of hypermethylated carcinomas was further divided in two subgroups, with different levels of methylation (CIMP-high and CIMP-low). This classification could be confirmed by methylation-specific multiplex ligation-dependent probe amplification. Hypermethylation was associated with a poor survival (Cox model p= 0.02). The transcriptome/methylation correlation showed 1741 genes (of 12250) negatively correlated; among the top genes were H19 and other tumor suppressors (PLAGL-1, G0S2, and NDRG2). The subgroups identified by the transcriptome adrenocortical have different levels of methylation. In conclusion, genomic alterations discriminate carcinomas from adenomas and contain prognostic information. The subgroups identified by the adrenocortical transcriptome profiles of different genomic alterations. Chromosomal alterations and abnormal methylation alter the expression of genes important for tumorigenesis.

A carcinogênese do córtex da supra-renal é um processo complexo que envolve alterações genéticas múltiplas e seqüenciais. Embora algumas dessas alterações já tenham sido caracterizadas, de modo geral estes mecanismos permanecem pouco compreendidos. Um conhecimento mais aprofundado dos mesmos não só levaria à descoberta de novos marcadores de prognóstico como também a alvos terapêuticos em potencial. A fim de melhor caracterizarmos os mecanismos envolvidos na progressão maligna do tumor e selecionarmos genes candidatos a serem marcadores de malignidade e alvos terapêuticos, nós estudamos os RNAs de uma linhagem celular derivada de um tumor adrenocortical maligno (NCI-H295A) e um espécime de tumor do córtex da supra-renal por \"Differential Display\" (DDRT-PCR). Foi selecionado um total de 317 transcritos únicos diferencialmente expressos, com base na análise densitométrica digital dos géis de DDRTPCR. A anotação funcional dos genes hiper-expressos mostrou relação com motilidade celular e proliferação. Entre os hipo-expressos foram identificados genes envolvidos na regulação de transcrição, síntese e processamento de RNA e remodelamento da cromatina. A expressão de dois genes entre os transcritos selecionados foi verificada por RT-PCR semi-quantitativa em 19 tumores adrenocorticais adultos e pediátricos, metastáticos e não metastáticos. Os genes da fucosiltransferase-11 e do supressor tumoral BCSC-1 (hiper- e hipo-regulado, respectivamente) encontraram-se diferencialmente expressos nos subgrupos específicos das 19 amostras tumorais. Em suma, o DDRT-PCR revelou-se uma ferramenta valiosa para uma análise global dos transcritomas do córtex da supra-renal e para selecionar genes com possível envolvimento na tumorigênese adrenocortical. Novos aspectos da biologia, progressão e possíveis alvos terapêuticos moleculares puderam ser vislumbrados. / There are important gaps in the present knowledge about adrenocortical tumorigenesis. For this reason we compared by Differential Display RNAs from a carcinoma-derived cell line (NCI-H295A) and a metastatic adrenocortical tumor and characterized 317 differentially expressed transcripts. The up-regulated genes are mainly related to cell motility and proliferation. Among the down-regulated genes, those involved in regulation of transcription, RNA synthesis and processing and chromatin remodeling were identified. Differential expression of FUTT11 and BCSC-1 tumor suppressor gene were confirmed in specific subsets of 19 adult and pediatric adrenocortical tumors and might serve as marker for malignancy. Our data revealed previously unknown aspects of adrenal tumorigenesis.

A carcinogênese do córtex da supra-renal é um processo complexo que envolve alterações genéticas múltiplas e seqüenciais. Embora algumas dessas alterações já tenham sido caracterizadas, de modo geral estes mecanismos permanecem pouco compreendidos. Um conhecimento mais aprofundado dos mesmos não só levaria à descoberta de novos marcadores de prognóstico como também a alvos terapêuticos em potencial. A fim de melhor caracterizarmos os mecanismos envolvidos na progressão maligna do tumor e selecionarmos genes candidatos a serem marcadores de malignidade e alvos terapêuticos, nós estudamos os RNAs de uma linhagem celular derivada de um tumor adrenocortical maligno (NCI-H295A) e um espécime de tumor do córtex da supra-renal por \"Differential Display\" (DDRT-PCR). Foi selecionado um total de 317 transcritos únicos diferencialmente expressos, com base na análise densitométrica digital dos géis de DDRTPCR. A anotação funcional dos genes hiper-expressos mostrou relação com motilidade celular e proliferação. Entre os hipo-expressos foram identificados genes envolvidos na regulação de transcrição, síntese e processamento de RNA e remodelamento da cromatina. A expressão de dois genes entre os transcritos selecionados foi verificada por RT-PCR semi-quantitativa em 19 tumores adrenocorticais adultos e pediátricos, metastáticos e não metastáticos. Os genes da fucosiltransferase-11 e do supressor tumoral BCSC-1 (hiper- e hipo-regulado, respectivamente) encontraram-se diferencialmente expressos nos subgrupos específicos das 19 amostras tumorais. Em suma, o DDRT-PCR revelou-se uma ferramenta valiosa para uma análise global dos transcritomas do córtex da supra-renal e para selecionar genes com possível envolvimento na tumorigênese adrenocortical. Novos aspectos da biologia, progressão e possíveis alvos terapêuticos moleculares puderam ser vislumbrados. / There are important gaps in the present knowledge about adrenocortical tumorigenesis. For this reason we compared by Differential Display RNAs from a carcinoma-derived cell line (NCI-H295A) and a metastatic adrenocortical tumor and characterized 317 differentially expressed transcripts. The up-regulated genes are mainly related to cell motility and proliferation. Among the down-regulated genes, those involved in regulation of transcription, RNA synthesis and processing and chromatin remodeling were identified. Differential expression of FUTT11 and BCSC-1 tumor suppressor gene were confirmed in specific subsets of 19 adult and pediatric adrenocortical tumors and might serve as marker for malignancy. Our data revealed previously unknown aspects of adrenal tumorigenesis.

Les corticosurrénalomes (CS), bien que rares, sont des tumeurs malignes du cortex surrénalien très agressives. Environ 30% des patients atteints de cancer surrénalien présentent des métastases au diagnostic et leur survie à 5 ans est inférieure à 20%. Les mécanismes à l’origine de la progression cancéreuse ne sont pas complètement élucidés. Leur compréhension est pourtant un préalable à la mise au point de traitements adaptés. Les mutations du gène P53 font parties des altérations génétiques les plus fréquentes dans les CS. Dans ce contexte, il est légitime d'étudier l'effet de l'inactivation de P53 spécifiquement dans les surrénales de souris. L'antigène T du virus SV40 est un oncogène qui se lie et inhibe P53 et RB. Le laboratoire dispose de souris transgéniques (modèle AdTAg) exprimant l’antigène T de SV40 dans le cortex surrénal qui développent des tumeursévolutives. L’objectif de ce travail était de caractériser l’ontogenèse de ces tumeurs et d’explorer les modifications cellulaires et moléculaires qui accompagnent leur progression maligne notamment en lien avec les signalisations β-caténine et IGF2/mTOR. Les souris AdTAg développent des tumeurs surrénaliennes récapitulant l’ensemble des caractéristiques décrites pour les CS humains. En effet, elles présentent une surmortalité à partir de 22 semaines associée à la survenue de métastases pulmonaires et hépatiques. Les tumeurs sont à l'origine d'une hypercorticostéronémie témoignant de leur différenciation stéroïdogénique. L'analyse du score de Weiss à différents stades montre une évolution de la bénignité vers la malignité. Cette progression tumorale s’accompagne d’une activation précoce de la voie mTOR et tardive de la voie Wnt/β-caténine. Ces deux voies de signalisation pourraient donc constituer des cibles thérapeutiques intéressantes. La deuxième partie du projet visait à utiliser ce modèle murin pour tester une thérapie anticancéreuse applicable au carcinome surrénalien. La rapamycine, un inhibiteur de mTOR, inhibe la prolifération cellulaire et induit une apoptose des cellules tumorales. Après 3 mois de traitement, une réduction significative du volume tumoral est constatée ainsi que la normalisation des taux de corticostérone. Nous avons également évalué l'effet antitumoral d'inhibiteurs de la voie Wnt/β-caténine: la quercetine et le PRI-724. La quercetine stoppe la progression tumorale en inhibant la prolifération cellulaire. Elle prolonge significativement la survie des souris AdTAg. Cependant, nous n'avons pas de preuve moléculaire d'inhibition de la voie Wnt/β-caténine dans les surrénales AdTAg et les mécanismes d'action de la molécule restent à élucider. A l'inverse, le PRI-724 semble être un inhibiteur spécifique de la voieWnt/β-caténine capable de bloquer l'interaction CBP/β-caténine. Un traitement de 2 mois permet une réduction significative du volume tumoral chez les souris AdTAg. La baisse d'expression de certains gènes cibles de l'interaction CBP/β-caténine témoigne d'une inhibition de la voie. Les résultats obtenus avec les inhibiteurs des voies mTOR et Wnt/β-caténine dans le modèle murin de CS sont prometteurs. L'utilisation de ces molécules pourrait donc être envisagée dans le traitement du CS. / Adrenocortical carcinoma (ACC) is a rare aggressive malignant tumor of adrenal cortex. 30% of patients have metastatic disease at diagnosis and the 5 year-survival rate is obtained inonly 20%. Unfortunately, the mechanisms of tumorigenesis are not well identified. Understanding these mechanisms could offer perspectives for new targeted therapies improving the survival in these patients. P53 inactivation in the adrenal cortex seems a good target to study its role in the tumorigenesis. Large T antigen of SV40 virus is an oncogene that fixes and inhibits P53 and RB. Our laboratory has mouse models expressing this antigen (AdTAg mouse model) in the adrenal cortex and developping progressive adrenal tumors. The initial objective was to characterize the ontogeny of these tumors, studying their molecular characteristics, especially β-catenin and IGF2/mTOR signaling, during the malignant progression. AdTAg mouse models develop adrenocortical tumors with characteristics that are identical to human ACC. They present pulmonary and liver metastases that lead to increased mortality rate from 22 weeks old. These tumors lead to hypercorticism that suggest their steroidogenic differentiation. Weiss score analyses indifferent ages show that these tumors progress from benign to malignant ones, associated with a precocious activation of mTOR pathway and tardive activation of Wnt/β-catenin pathway. These pathways are thus interesting therapeutic targets. The second part of this thesis was concentrated on the anti-cancer treatment trials. Rapamycin, an mTOR inhibitor inhibits cell proliferation and increases cell apoptosis in these tumors. After 3 months of treatment, the tumor burden was significantly reduced and corticosterone levels were normalized. We have also evaluated effects of Wnt/ β-catenininhibitors, Quercetin and PRI-742, in our mouse models. Quercetin inhibits tumor proliferation and progression and it extends the survival rate of AdTAg mice. Surprisingly, this effect was independent of Wnt/β-catenin activity and the molecular mechanisms remain to be elucidated. Inversely, PRI-724 seems to be a specific inhibitor of this pathway, blocking the interaction between CBP and β-catenin. A treatment of 2 months reduced significantly the tumor volume in AdTAg mice. This effect was through the inhibition of CBP and β-catenininteraction and signaling. These results encourage using the inhibitors of mTOR and Wnt/β-catenin pathway offering promising targets to improve the survival in patients with ACC.

The DDT metabolite 3-methylsulfonyl-DDE (3-MeSO2-DDE) is bioactivated by cytochrome P450 11B1 (CYP11B1) in the adrenal cortex of mice and forms irreversibly bound protein adducts, reduces glucocorticoid secretion, and induces cell death selectively in cortisol-producing adrenocortical cells. 3-MeSO2-DDE has therefore been proposed as a lead compound for an improved adrenocortical carcinoma (ACC) therapy. The aims of this thesis were to (1) develop in vitro test systems based on murine and human adrenocortical cell lines and to (2) investigate the mechanisms behind 3-MeSO2-DDE toxicity in adrenocortical cells. The cytotoxic and endocrine-modulating effects of 3-MeSO2-DDE were compared to those of o,p′-DDD (mitotane), the current ACC therapy, and to those of several structurally analogous compounds in both murine and human cell lines. 3-MeSO2-DDE bioactivation and cytotoxicity proceeded in a similar manner in the murine adrenocortical Y-1 cell line as in mice in vivo. The effects were highly structure-specific. Moreover, 3-MeSO2-DDE formed irreversibly bound protein adducts and caused cell death also in the human H295R cell line, and was slightly more cytotoxic than o,p′-DDD. However, 3-MeSO2-DDE toxicity in human cells was not affected by the CYP11B1 inhibitor etomidate, suggesting that bioactivation in human cells is performed by additional/other enzyme(s) than CYP11B1. 3-MeSO2-DDE generated biphasic responses in cortisol and aldosterone secretion and in expression levels of the steroidogenic genes CYP11B1, CYP11B2, and StAR. Such hormesis-like responses were not seen for o,p′-DDD or the precursor DDT metabolite p,p′-DDE. In addition, the two o,p′-DDD enantiomers (R)-(+)-o,p′-DDD and (S)-(-)-o,p′-DDD exhibited slight differences in cytotoxic and endocrine-modulating activity in H295R cells. In conclusion, this thesis  provides  extended  knowledge  on  the  mechanisms  of  action  of 3-MeSO2-DDE and points out important differences in effects between murine and human cells. Lead optimisation studies of 3-MeSO2-DDE using the herein presented in vitro test systems are ongoing.

Les cortico-surrénalomes (CCS) sont considérés comme des tumeurs malignes endocriniennes rares, associées à un pronostic sombre. Les trois mécanismes moléculaires les plus fréquemment altérés dans les CCS comprennent les mutations inactivatrices du gène suppresseur de tumeur TP53,la surexpression de IGF-II et l'activation constitutive de la voie de signalisation Wnt/β-caténine. En utilisant des modèles de souris transgéniques, nous avons montré que ces altérations, même combinées, ne sont pas suffisantes pour permettre la progression maligne.Nous avons précédemment identifié l'histone méthyltransférase EZH2 comme le modificateur d'histone le plus dérégulé dans les CCS. Nous avons également montré que sa surexpression est associée à une progression tumorale et à un mauvais pronostic. Cependant, les mécanismes sous-jacents de cette agressivité sont largement inconnus. Dans cette étude, nous avons cherché à identifier les gènes cibles de EZH2 dans les CCS, qui sont soient activés, soient réprimés. Ainsi, nous avons effectué une analyse bio-informatique des données du transcriptome de trois cohortes de patients porteurs de CCS. L’analyse montre une forte corrélation entre la surexpression de EZH2 et les gènes régulés positivement, suggérant un rôle majeur d’inducteur transcriptionnel de EZH2 dans les CCS. Nous avons montré que cette activité positive repose sur une interaction entre EZH2 et E2F1, qui entraîne la surexpression de gènes impliqués dans la régulation du cycle cellulaire et la mitose tels que RRM2,PTTG1 et PRC1/ASE1. Nous avons montré que l'inhibition de RRM2 par ARN interférent ou traitement pharmacologique avec le GW8510 inhibe la croissance cellulaire, la capacité à combler les blessures, la croissance clonogénique, la migration et induit l'apoptose des cellules H295R en culture. En revanche, l'expression du facteur pro-apoptotique NOV/CCN3 est diminuée dans les CCS, ce qui est corrélé au développement de tumeurs agressives. Nos analyses moléculaires montrent que l'inhibition de EZH2 augmente l'expression de NOV/CCN3, suggérant que la surexpression de EZH2 pourrait favoriser la progression maligne des CCS en inhibant les stimulateurs de l'apoptose. Le facteur NOV a déjà été identifié comme cible négative du récepteur nucléaire SF1 dans les cellules du CCS, bien que les mécanismes moléculaires à l'origine de cette inhibition n'aient pas été identifiés. De manière intéressante, dans le cancer de la prostate, l'expression de NOV est inhibée par le récepteur des androgènes AR, grâce au recrutement de EZH2 qui pose la marque répressive H3K27me3. Nous avons pu identifier une coopération similaire entre SF1 et EZH2 pour réprimer l'expression de NOV et bloquer ainsi l'apoptose dans les CCS.Au total, ces résultats identifient SF1 et E2F1 comme deux partenaires indépendants de EZH2, induisant la répression de facteurs pro-apoptotiques et l'activation des gènes du cycle cellulaire respectivement, conduisant ainsi à l'agressivité des CCS. / Adrenocortical carcinomas (ACC) are regarded as rare endocrinemalignancies associated with dismal prognosis. The three common molecularmechanisms predominantly altered in ACC include inactivating mutations of theTP53 tumor suppressor gene, overexpression of IGF-II and constitutive activationof the Wnt/β-catenin signaling pathway. Using transgenic mouse models, wehave shown that these alterations, even when combined together, were notsufficient to induce malignant progression.We previously identified the histone methyltransferase EZH2 as the mostderegulated histone modifier in ACC. We have also shown that its overexpressionis associated with tumor progression and poor prognosis. Yet, the mechanismsunderlying this aggressiveness are largely unknown. Here, we aimed to identifyEZH2 target genes in ACC, which are either activated or repressed.Thus, we conducted a bio-informatics analysis of transcriptome data fromthree cohorts of ACC patients. The analysis showed a strong correlation betweenhighly expressed EZH2 and positively regulated genes suggesting a major role of‘transcriptional inducer‘ for EZH2 in ACC. We have shown that this positiveactivity relies on an interaction between EZH2 and E2F1 that results in theupregulation of genes implicated in cell cycle regulation and mitosis such asRRM2, PTTG1 and PRC1/ASE1. We showed that Inhibition of RRM2 by RNAinterference or pharmacological treatment with GW8510 inhibits cellular growth,wound healing, clonogenic growth, migration and induces apoptosis of H295Rcells in culture.In contrast, expression of the pro-apoptotic factor NOV/CCN3 is decreasedin ACC, which is correlated with development of aggressive tumours. Ourmolecular analyses show that EZH2 inhibition increases expression ofNOV/CCN3, suggesting that EZH2 overexpression may also favour malignantprogression in ACC by inhibition of apoptosis stimulators. NOV has previouslybeen identified as a negative target of the nuclear receptor SF1 in ACC cells,although the molecular mechanisms underlying this inhibition were unidentified.Interestingly, in prostate cancer, NOV expression is inhibited by the androgenreceptor, through recruitment of EZH2 and deposition of the H3K27me3 mark.We have been able to identify a similar cooperation between SF1 and EZH2 tosuppress NOV expression and block apoptosis in ACC.Altogether, these findings identifiy SF1 and E2F1 as two independentpartners of EZH2, inducing repression of proapoptotic factors, and activation ofcell cycle genes respectively, thus leading to aggressiveness of ACC.

Introdução: A 3-hidroxi-3-metilglutaril coenzima A redutase (HMGCR) é a enzima limitante da via do mevalonato. Esta via, que tem como produto final o colesterol, gera inúmeros subprodutos, como os isoprenóides, essenciais para modificação pós-traducional de várias proteínas envolvidas em proliferação e crescimento celular. Em tecidos esteroidogênicos (por exemplo, córtex adrenal), a HMGCR pode desempenhar um papel tanto no controle do crescimento e proliferação celular quanto na esteroidogênese. HMGCR está hiperexpressa em várias formas de neoplasias humanas inclusive em tumores adrenocorticais (ACTs), mas a sua importância na biologia dos ACTS é desconhecida. Objetivos: Avaliar o padrão de expressão da HMGCR e outros genes que participam na economia de colesterol e esteroidogênese em ACTs adultos e pediátricos; avaliar o efeito do inibidor da HMGCR lovastatina na via proliferativa MAPK; e analisar os efeitos de vários inibidores da via mevalonato na viabilidade de células NCI-H295A. Casuística e métodos: Analisamos a expressão do RNAm por PCR em tempo real dos genes HMCGR, FDFT1, SCARB1, LDLR StAR, TSPO, CYP11A1, CYP11B1, CYP17A1, CYP21A1 e HSD3B1, em ACTs, incluindo 27 tumores de adultos: [17 adenomas (ACA) e 10 carcinomas (ACC)]; 21 tumores de crianças [13 adenomas (PAD) e 8 carcinomas (PAC)]. Um pool comercial de RNA poli A obtido de córtex adrenal normal humano foi utilizado como amostra referência. A fosforilação da proteína ERK 1/2 (efetor final da via MAPK) no extrato intracelular de células NCI-H295A após tratamento com lovastatina foi avaliada através de SDS-PAGE seguido por immunoblot com anticorpos específicos. A ação sob a viabilidade celular em células NCI-H295A dos inibidores da via mevalonato foi realizada por análise colorimétrica. Resultados: A maioria dos ACTs de adultos apresentou expressão diminuída de StAR, TSPO, CYP11A1, CYP11B1, CYP17A1, CYP21A1 e HSD3B1 e hiperexpressão da HMGCR. Neste grupo, a expressão relativa dos genes StAR, TSPO, CYP11B1, CYP21A1 e HSD3B1 foi significativamente menor nos ACCs (p <0,02). O gene LDLR não foi diferencialmente expresso na maioria dos ACTs do grupo adulto, enquanto que o gene SCARB1 e FDFT1 estavam hipoexpressos nestes tumores, independentemente do comportamento biológico. A análise de grupamento mostrou que ACCs formam um grupo distinto dos ACAs, com exceção de uma amostra. Com relação aos tumores do grupo pediátrico, não houve diferença na expressão dos genes estudados entre PAD e PAC. A expressão de HMGCR e TSPO se correlacionou inversamente, enquanto uma significativa correlação positiva entre StAR, CYP11A1, CYP11B1, CYP17A1, CYP21A1 e HSD3B1 foi observada nos ACTs do grupo adulto. O tratamento de células NCI-H295A com lovastatina provocou uma diminuição na fosforilação ERK 1/2. A inibição da HMGCR e isoprenilação de proteínas diminuiu drasticamente a viabilidade das células NCI-H295A, ao contrário do bloqueio específico da síntese de colesterol, que não apresentou efeito sobre a viabilidade celular. Conclusão: A hipoexpressão de genes relacionados à esteroidogênese e, em menor grau, a hiperexpressão da HMGCR caracterizam os ACCs. A hiperexpressão da HMGCR leva a um aumento na isoprenilação de proteínas e não da produção de colesterol, pois os principais genes envolvidos na esteroidogênese estão hipoexpressos e o bloqueio específico da síntese de colesterol não interferiu na viabilidade das células NCI-H295A. A isoprenilação de proteínas (por exemplo, Ras) é um evento crucial para viabilidade das células NCI-H295A e está envolvida na ativação de cascatas de sinalização de proliferação celular. A via mevalonato é um alvo potencial para o tratamento dos tumores adrenocorticais / Introduction: 3-hydroxy-3-methylglutaryl coenzime A reductase (HMGCR) is the rate-limiting enzyme of the mevalonate pathway, which generates isoprenoids for both post-translational modification of several proteins involved in cell growth and proliferation and biosynthesis of cholesterol. Therefore, in steroidogenic tissues (e. g. adrenal cortex), HMGCR may play a role in both growth control and steroidogenesis. HMGCR is overexpressed in several forms of human neoplasms incluiding adrenocortical tumors (ACTs), but its importance in the biology of ACTs is unknown. Objective: To assess the expression pattern of HMGCR, and other genes involved in cholesterol economy and steroidogenesis in pediatric and adult ACTs. To evaluate the impact of a HMGCR inhibitor lovastatin on proliferative pathway- MAPK - of NCI-H295A cells; to evaluate the effects of various mevalonate pathway inhibitors in NCI-H295A cells viability. Methods: We analyzed HMGCR, FDFT1, LDLR, SCARB1, StAR, TSPO, CYP11A1, CYP11B1, CYP17A1, CYP21A1 and HSD3B1 mRNA expression by real-time RT-PCR in ACTs [Adult tumors: 14 adenomas (ACA) and 11 carcinomas (ACC); Pediatric tumors: 13 adenomas (PAD) and 8 carcinomas (PAC)]. A commercial pool of normal human adrenal cortex poly A RNA was used as reference sample. We assess ERK phosphorylation after treatment with lovastatin through SDS-PAGE of intracellular extract followed by immunoblotting with specific antibodies. Action of mevalonate pathway inhibitors on cellular viability was assessed by colorimetric assay. Results: Most adult ACTs showed decreased expression of StAR, TSPO, CYP11A1, CYP11B1, CYP17A1, CYP21A1 and HSD3B1 and overexpression of HMGCR. In this group, the relative expressions of TSPO, StAR, CYP11B1, CYP21A1 and HSD3B1 were significantly lower in the ACCs (P<0.02). LDLR was not differentially expressed in most of adults ACTs, while FDFT1 and SCARB1 were hypoexpressed in this group, independently of biological behavior. Cluster analysis showed that adult ACCs form a group distinct from adrenocortical adenomas, with exception of one carcinoma sample. Regarding tumors of the pediatric group, no differences in the expression of evaluated genes were found between PAD and PAC. The expression of HMGCR and TSPO correlated negatively while a significantly positive pairwise correlation among StAR, CYP11A1, CYP11B1, CYP17A1, CYP21A1 e HSD3B1 was observed in adults ACTs. Lovastatin treatment leads a decreased ERK phosphorylation in NCI-H295A cells. Inhibition of HMGCR, farnesyl syntase and protein isoprenylation decreased drastically NCI-H295A viability unlike the specific block of cholesterol biosyntheses that did not have any effect on cell viability. Conclusion: The hypoexpression of genes related to steroidogenesis and (to a lesser degree) the overexpression of HMGCR characterizes ACCs. HMGCR overexpression cause an increased isoprenylation of proteins rather than cholesterol production for steroidogenesis or membrane cellular integrity since the key regulators involved in this process were downregulated and specific inhibition of cholesterol did not affect NCI-H295A viability. Isoprenylation of proteins is a crucial event for NCI-H295A viability and is involved in signaling cascades (e.g. Ras). Mevalonate pathway is a potential target for treatment of adrenocortical tumors

Les carcinomes de la cortico-surrénale (CCS) sont des tumeurs de mauvais pronostic et les thérapies sont encore limitées. La chirurgie reste à ce jour le seul traitement efficace. La compréhension des mécanismes de la tumorigenèse cortico-surrénalienne et l'identification des gènes et des voies de signalisation impliquées sont nécessaires pour identifier de nouvelles cibles thérapeutiques. Ces dernières années, plusieurs études de génomique ont été réalisées sur des cohortes indépendantes de CCS et ont mis en évidence l'existence de deux groupes de CCS ayant des profils d’expression génique particuliers et associés à des pronostics de survie différents. Il a aussi été identifié de fréquentes mutations touchant les gènes TP53 et CTNNB1 (β-caténine). De plus, l'activation aberrante de la voie WNT/β-caténine est associée au groupe des CCS agressifs. Enfin, des analyses des altérations génomiques par puce SNP et le séquençage de l’exome de cohortes de CCS a permis de préciser les fréquences des mutations de TP53 (~18%) et CTNNB1 (~14%) mais a aussi mis en évidence des mutations et des délétions homozygotes au niveau du gène ZNRF3 (Zinc And Ring Finger 3) dans environs 20% des CCS. ZNRF3 a été montré comme jouant un rôle de régulateur négatif de la voie WNT/β-caténine. Par conséquent, la voie de signalisation WNT/β-caténine est la voie la plus fréquemment altérée dans les CCS (~40%). L’objectif de mon projet était d’étudier comment l’activation constitutive de la voie WNT/β-caténine pouvait participer à la tumorigenèse cortico-surrénalienne, puis d'essayer de comprendre plus spécifiquement le rôle des altérations de ZNRF3 dans le développement et/ou l'agressivité des CCS. En combinant des analyses de transcriptomes de modèles cellulaires et de cohortes de CCS, nous avons établi une signature robuste cortico-surrénalienne de l'activation de la voie WNT/β-caténine. Parmi les gènes de cette signature, nous avons montré que AFF3 était une cible transcriptionnelle de la β-caténine et qu'il était capable de transmettre en partie les effets oncogèniques de la voie WNT/β-caténine dans les cellules cortico-surrénaliennes. En effet, son invalidation entraîne l'apoptose et diminue la prolifération des cellules cortico-surrénaliennes à l'image de l'invalidation de la β-caténine. La surexpression d’AFF3 altère l’organisation des speckles nucléaires et la localisation de CDK9/CyclinT1 impliqués respectivement dans l'épissage des ARNm et la transcription des gènes. ZNRF3 est le gène le plus fréquemment altéré dans les CCS alors qu'il l'est très peu dans les autres types de cancers. ZNRF3 est une E3 ubiquitin ligase qui entraîne l'internalisation et la dégradation des récepteurs Frizzleds de la voie WNT. Nous avons montré que ZNRF3 agit bien comme un gène suppresseur de tumeur dans les cellules cortico-surénaliennes humaines H295R. En effet la surexpression de ZNRF3 diminue la prolifération et augmente l’apoptose cellulaire de ces cellules. Nous avons aussi montré qu'à l'image d'autres régulateurs négatifs de la voie WNT comme AXIN2, ZNRF3 est un gène cible de la voie WNT/β-caténine dans la corticosurrénale. De manière intéressante, les altérations du gène ZNRF3 ne sont pas retrouvées dans des tumeurs présentant une forte activation de la voie de signalisation WNT/β-caténine, suggérant l'implication d'autres voies de signalisation. Nous avons identifié des partenaires protéiques de ZNRF3 par des expériences d'immunoprécipitation / spectrométrie de masse. Nous avons montré que ZNRF3 interagit avec la sous unité catalytique de la pompe NA+/K+, ATP1A1. Cette interaction altère le fonctionnement de la pompe NA+/K+ conduisant à des modifications du flux de Ca2+ intracellulaire. L'ensemble de ces travaux a permis de mieux comprendre comment la voie WNT/β-caténine participe à l'agressivité des cancers de la corticosurrénale et de montrer qu'AFF3 est essentiel pour les effets oncogéniques de cette voie. (...) / Adrenocortical carcinomas are rare tumors with poor prognostic and limited therapy. Up to now, surgery remains the only curative therapy. A better understanding of tumor biology and molecular prognostic factors would help to select relevant therapeutic targets and to develop innovative therapeutic strategies. In the last years, different genomic studies on independent cohorts of ACC have identified two subgroups of cancers with two distinguished profiles of genes expression and two different survival rates. Frequents alterations of CTNNB1 and TP53 are identified in ACC. Moreover, aberrant activation of WNT/β-catenin pathway in ACC is associated with lower overall survival. Using a combination of genomic approaches, we and others have recently analyzed independent cohorts of ACC. These works confirmed recurrent alterations in CTNNB1 (~14%) and TP53 (~18%), but also revealed new loci not previously reported to be altered in ACC. Strikingly, ZNRF3 (zinc and ring finger 3) was the most frequently altered gene (~20%). ZNRF3 encodes a protein that acts as a negative regulator of Wnt/β-catenin pathway. The Wnt/β-catenin pathway represents the most frequently altered pathway in ACC (~40%). The aim of my project was to study how the aberrant activation of WNT/β-catenin pathway could participate to adrenal tumorigenesis and then to identify more specifically the role of ZNRF3 alterations in development/aggressiness of ACC. By a combination of transcriptomic analysis on two cohorts of ACC and on H295R adrenocortical cells, we identified a list of genes whose expression is correlated to the WNT/β-catenin activation. Among these genes, we show that AFF3 is essential to mediate the effect of activation the WNT/β-catenin pathway in adrenocortical cancer. Indeed, AFF3 is a direct target gene of β-catenin and its silencing in H295R adrenocortical cells induces a decreased cell proliferation and an increased apoptosis similar to that induced by β-catenin silencing. Moreover, AFF3 overexpression altered the structure of nuclear speckles and the localization of CDK9/CyclinT1, which are respectively involved in mRNA splicing and transcription. ZNRF3 (zinc and ring finger 3) was the most frequently altered gene (20%) in ACC. ZNRF3 had never been frequently associated with other tumour types. ZNRF3 encodes a protein that had been described as cell-surface transmembrane E3 ubiquitin ligases, acting as negative regulators of Wnt/β-catenin signaling, by promoting the degradation of Wnt ligand receptors (Frizzled receptors). We show that ZNRF3 act as a tumor suppressor gene in adrenocortical cell line H295R. Indeed the overexpression of ZNRF3 decreases cell proliferation and increases apoptosis. We demonstrate also that ZNRF3 is a target gene of WNT/β-catenin pathway. ZNRF3 alterations have less effect on expression of WNT/β-catenin target genes than CTNNB1 mutations in ACC. Moreover, our results with ZNRF3 overexpression in H295R adrenocortical cells suggest that ZNRF3 is also involved in βcatenin independant-pathway(s) to mediate its effects on apoptosis. Using mass spectrometry analysis, we identified that ZNRF3 interacts with ATP1A1 (ATPase Na+/K+ Transporting Subunit Alpha 1), affecting the activity of the Na+/K+ ATPase pump in adrenocortical cells. These results provide a better understanding of the biological process of WNT/βcatenin pathway activation in ACC with AFF3 as new target of this pathway. Moreover, our data provide insight into the tumor suppressor role of ZNRF3 in ACC and uncovers an additional role of ZNRF3 on Na+/K+ ATPase pump activity.