Made available in DSpace on 2014-10-09T12:27:56Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:00:14Z (GMT). No. of bitstreams: 0 / As lesões dermatológicas submetidas à terapia com fontes de radiação podem apresentar diferentes padrões de malignidade. Os tumores de pele mais comumente encontrados nos serviços de radioterapia são os carcinomas. A radioterapia de lesões dermatológicas é realizada com feixes de radiação de baixa penetração como os raios-X de ortovoltagem, feixes de elétrons e fontes radioativas (192Ir, 198Au, e 90Sr) arranjadas em moldes superficiais ou aplicadores metálicos. O presente trabalho teve como objetivo analisar o perfil de distribuição de dose terapêutica produzida por fontes de radiação utilizadas em procedimentos radioterápicos em lesões superficiais da pele. As medidas experimentais, para as análises dosimétricas das fontes de radiação, foram comparadas com cálculos obtidos no sistema computacional baseado no Método de Monte Carlo. Os resultados obtidos com os cálculos computacionais através do código MCNP-4C apresentaram uma boa concordância com as medidas experimentais. As comparações das medidas experimentais com os cálculos obtidos através do código MCNP-4C, foram utilizadas para validar os cálculos e assim possibilitar o uso de dados de simulação para aplicação em casos clínicos de rotina. A comparação entre diferentes modalidades podem fornecer um indicativo dos procedimentos mais adequados em cada caso clínico. / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Made available in DSpace on 2014-10-09T12:38:33Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:05:10Z (GMT). No. of bitstreams: 1 06004.pdf: 4196576 bytes, checksum: 707f1ed9565795d26cc6aa938c5f4995 (MD5) / Dissertacao (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN/CNEN-SP

Made available in DSpace on 2014-10-09T12:33:03Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:06:05Z (GMT). No. of bitstreams: 0 / A terapia fotodinâmica (PDT) é uma alternativa promissora de tratamento para lesões pré-cancerosas e para câncer de pele não-melanoma, como o carcinoma espinocelular, agressivo e potencialmente metastático. Visando melhorar a eficiência da terapia fotodinâmica de carcinoma espinocelular de pele, este estudo otimizou o tempo para início da terapia, avaliou a eficácia dos fotossensibilizadores ácido aminolevulínico (ALA- 20%) e o metil-ester aminolevulínico (MEALA-10%) e verificou o coeficiente de atenuação relativo à pele normal dos grupos experimentais, por meio de Tomografia por Coerência Óptica. Para a indução do tumor foi realizada a carcinogênese química (DMBA/TPA) por um período de 28 semanas. A espectroscopia de fluorescência foi utilizada para monitoração da emissão da molécula de protoporfirina IX, induzida pelo ALA e MEALA. A aquisição de dados a cada 30 minutos totalizando um período de 360 minutos, permitiu verificar a máxima incorporação de ALA e MEALA em 300 e 330 minutos após a aplicação, respectivamente. Após a otimização foi realizada a PDT, avaliação clínica, histopatológica e análise por OCT dos grupos experimentais, por meio das quais verificou-se maior eficiência do grupo tratado com MEALA. No período de 20 dias, o percentual de lesões com redução de área maior que 50%, foi de 33% na PDT com ALA e 83% para o MEALA. Os coeficientes de atenuação ópticos para os grupos com neoplasia foram maiores do que os do grupo controle. Os grupos tratados com PDT apresentaram valores de coeficiente de atenuação que se aproximam dos valores obtidos para a pele sadia, evidenciando a resposta ao tratamento. Entretanto para ambos os fotossensibilizadores utilizados, a PDT mostrou-se eficaz quando iniciada nos tempos determinados neste estudo, e a técnica de OCT mostrou-se uma potencial ferramenta na avaliação deste tratamento. / Dissertação (Mestrado) / IPEN/D / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

Made available in DSpace on 2014-10-09T12:33:13Z (GMT). No. of bitstreams: 0 / Made available in DSpace on 2014-10-09T14:06:12Z (GMT). No. of bitstreams: 0 / O diagnóstico precoce de tumores e metástase constitui atualmente o elemento de maior impacto dentro das políticas de saúde públicas contra o câncer. No câncer de mama e melanoma, a técnica de biópsia de linfonodo sentinela, para o diagnostico de metástase, tem sido muito utilizada evitando a dissecção total dos nodos da região anatômica afetada, e permitindo definir com precisão o procedimento terapêutico a utilizar. O objetivo principal deste trabalho centrou-se no desenvolvimento de conjugados radiomarcados de dextran-manose para diagnóstico, utilizando o núcleo de tecnécio altamente estável, [99mTc(CO)3]+. A cisteína, ligante tridentado, foi incorporada na estrutura dos conjugados, como agente quelante do Tecnécio-99m. As condições de marcação definidas para os produtos avaliados garantiram altos valores de pureza radioquímica (>90%) e atividade específica (>59,9 MBq/nmol) assim como uma alta estabilidade in vitro. Os conjugados de dextran-cisteína-manose demonstraram uma captação superior (4 vezes maior) nos nodos linfáticos em relação aos homólogos que não possuíam manose na estrutura. O conjugado de dextran-cisteína-manose de 30 kDa radiomarcado (99mTc-DCM2) foi o traçador com melhor desempenho biológico entre os avaliados à diferentes atividades injetadas. Demonstrou-se que concentrações superiores a 1 M favorecem a retenção do produto nos nodos linfáticos. As comparações com radiofármacos já utilizados no Brasil (Dextran-500 e Fitato) para detecção de linfonodo sentinela evidenciaram a superioridade do 99mTc-DCM2. / Tese (Doutoramento) / IPEN/T / Instituto de Pesquisas Energeticas e Nucleares - IPEN-CNEN/SP

CoordenaÃÃo de AperfeiÃoamento de Pessoal de NÃvel Superior / The Epstein-Barr virus (EBV) has been related to the tumorigenesis of the gastric carcinomas, varying from 1.3-19.3% according to the studied population. Several studies have demonstrated strong evidences of its relation in this process, such as the monoclonality of the viral genome and its the presence in almost all tumor cells. However, most of the mechanisms used by the virus to control this process are still unknown. In this context, the present study aimed to investigate the frequency of the EBV and the association with the BCL-2, BAX and c-MYC proteins. Therefore, 100 cases of gastric carcinoma (67 males and 33 females), obtained from two hospitals in Fortaleza, were assessed to detect the EBV by PCR and in situ hybridization (aimed to the EBER1 transcript) using the standard method and GenPointÂ. Immunohistochemistry technique was done to evaluate the expression of the referred cellular proteins, by streptavidin-biotin-peroxidase method. The distribution by sex, age, tumor anatomic site and the histopathologic analysis, in general, reproduced the pattern of the world scientific bibliographies. Regarding virus detection by in situ hybridization, 8 (8%) cases were positive, 6 of these had shown diffuse pattern of staining, and 2 had demonstrated focal pattern. From 100 cases, only 2 presented infected lymphocytes. In general, the EBV demonstrated higher association with: males (87.5%[p=0.265]), tumors situated in the cardia (37.5% [p=0.549]), advanced stage (IIIB and IV), intestinal type (87.5%[p=0.136]), and moderately differentiated (75%).There were no EBV-positive cases which exhibited BCL-2 staining. Although the BAX and the c-MYC (nuclear) proteins have demonstrated significant positivity index and scores averages in the EBV-positive group, these were lower than the values of the EBV-negative group, notably the c-MYC nuclear protein (Mann-Withney test LI p=0.039 and HS p=0.045). The cytoplasmic staining of the c-MYC protein revealed slightly higher staining values in the EBV-positive group. The balance between the BCL-2 and BAX proteins demonstrated that the majority of the evaluated cases had exhibited apoptosis-orientation, however 62.3% of the EBV-positive cases exhibited equilibrium between these proteins. Twenty-nine cases (28 negative and 1 positive) were submitted to the biotinyl tyramide system (in situ hybridization method - GenPointÂ), demonstrating the same results obtained by the standard technique. From the 61 cases assessed by PCR, 35 (57.4%) were positive, being verified a low concordance index (kappa = -0.026 [Â0.069]) with the standard in situ hybridization technique. The 30bp deletion of LMP1 gene was investigated in 24 out of 35 positive cases, being verified in 37.5% of these. The results obtained in the present study, concerning the EBV frequency and the correlation with clinic-histopathologic data, reproduced findings of researches done in several world regions. The correlation with the proteins suggests that in vivo the virus is not related to the overexpression of BCL-2 and c-MYC (nuclear) that could act in synergism to promote the tumor development. The suppression of the BAX expression might represent a viral mechanism for apoptosis inhibition. The results of the cytoplasmic c-MYC point to a possible involvement of the EBV with transport mechanisms of the nuclear membrane, resulting in its accumulation in the cytoplasm. The low frequency of infected lymphocytes indicates that they are not the main responsible of the high number of positivity in the PCR technique. It could be, at least in part, due to the infected normal and/or pre-neoplastic epithelium, suggesting a new latency pattern which not express the EBER1. / O vÃrus Epstein-Barr (EBV) tem sido associado com a tumorigÃnese dos adenocarcinomas gÃstricos, variando entre 1,3-19,3% de acordo com a populaÃÃo estudada. Diversos estudos tÃm demonstrado importantes evidÃncias do envolvimento do EBV nesse processo, tais como a monoclonalidade do genoma viral e a presenÃa do vÃrus em quase todas as cÃlulas tumorais do sitio primÃrio e em cÃlulas metastÃticas. No entanto, os mecanismos utilizados pelo vÃrus para orquestrar a transformaÃÃo tumoral, ainda nÃo foram totalmente elucidados. Neste contexto, o presente estudo objetivou investigar a freqÃÃncia do EBV e a associaÃÃo com as proteÃnas BCL-2, BAX e c-MYC. Para tanto, 100 casos de adenocarcinomas gÃstricos (67 homens e 33 mulheres), obtidos de dois hospitais de Fortaleza, foram analisados quanto à presenÃa do EBV, detectado atravÃs das tÃcnicas de PCR e de hibridaÃÃo in situ (direcionada ao transcrito viral EBER1) pelo mÃtodo usual e GenPointÂ. Procedeu-se tambÃm, estudo imuno-histoquÃmico das referidas proteÃnas celulares, atravÃs do mÃtodo da estreptoavidina-biotina-peroxidase. A distribuiÃÃo por sexo, idade, sÃtio anatÃmico do tumor e as anÃlises histopatolÃgicas, de modo geral, reproduziram as tendÃncias da literatura mundial. Pela tÃcnica de hibridaÃÃo in situ, 8 (8%) casos foram positivos, 6 destes apresentaram marcaÃÃo difusa e 2 apresentaram marcaÃÃo focal. Apenas 2 apresentaram linfÃcitos infectados. De modo geral, o EBV apresentou maior associaÃÃo com o sexo masculino (87,5% [p=0,265]), com tumores situados na cÃrdia (37,5% [p=0,549]), de estadiamento avanÃado (IIIB e IV), do tipo intestinal (87,5% [p=0,136]) e moderadamente diferenciados (75%). Nenhum dos casos EBV-positivos exibiram marcaÃÃo para BCL-2. Embora as proteÃnas BAX e c-MYC (nuclear) apresentaram Ãndices de positividade e mÃdias de escores significativos no grupo EBV-positivo, estes foram inferiores aos valores do grupo EBV-negativo, sobretudo a proteÃna c-MYC nuclear (Teste de Mann-Withney LI p=0,039 e HS p=0,045). A marcaÃÃo citoplasmÃtica da proteÃna c-MYC revelou valores de marcaÃÃo discretamente superiores no grupo EBV-positivo. O balanÃo entre as proteÃnas BCL-2 e BAX demonstrou que a maioria dos casos estudados apresentavam tendÃncia à apoptose, mas 62,5% dos casos EBV-positivos exibiram um equilÃbrio. Vinte e nove casos (28 negativos e 1 positivo) foram submetidos a outro mÃtodo de hibridaÃÃo in situ que emprega o sistema da biotinil-tiramida (GenPointÂ),demonstrando resultados idÃnticos aos obtidos pela tÃcnica convencional. De 61 casos analisados atravÃs da tÃcnica de PCR, 35 (57,4%) foram positivos, sendo constatado um baixÃssimo Ãndice de concordÃncia (kappa = -0,026 [Â0,069]) com a tÃcnica de hibridaÃÃo in situ. Em 24/35 casos positivos, a deleÃÃo de 30pb do gene LMP1 foi investigada, sendo constatada em 37,5% destes. Os resultados obtidos no presente estudo quanto à freqÃÃncia do EBV e a correlaÃÃo com critÃrios clÃnico-histopatolÃgicos, reproduziram os achados de estudos realizados em diversas partes do mundo. A correlaÃÃo com as proteÃnas sugere que in vivo, o vÃrus nÃo esteja relacionado com a expressÃo de BCL-2 e de c-MYC (nuclear), que poderiam atuar em sinergismo favorecendo o desenvolvimento tumoral. A supressÃo da expressÃo de BAX, pode representar um mecanismo viral para inibiÃÃo da apoptose. Os resultados da c-MYC citoplasmÃtica apontam para um possÃvel envolvimento do EBV com mecanismos de transporte da membrana nuclear, determinando o acÃmulo da proteÃna no citoplasma. A baixa freqÃÃncia de linfÃcitos infectados indica que os mesmos nÃo sÃo os principais responsÃveis pela elevada positividade da tÃcnica de PCR, devendo ser ao menos em parte, decorrente de epitÃlio normal e/ou prÃ-neoplÃsico infectado sugerindo um padrÃo de latÃncia que nÃo expresse EBER1.

Les carcinomes sarcomatoïdes sont un sous type rare de cancer bronchique non à petites cellules (CBNPC). Leur pronostic semble plus défavorable que celui des autres sous-types de CBNPC. Notre équipe travaille sur le démembrement moléculaire de ces tumeurs. Dans ce travail, nous démontrons que les carcinomes sarcomatoïdes sont chimiorésistants aux sels de platine à partir d'étude in vivo et in vitro (cultures primaires) comparativement aux autres sous-types de CBNPC. Nous démontrons que tumeurs partagent les caractéristiques phénotypiques des CBNPC tant d'un point de vue immunohistochimique que moléculaire, confortant la classification OMS. Il est possible que ces tumeurs dérivent de cellules souches de CBNPC ou utilisent un processus de transition épithélio-mésenchymateuses. Les spécificités de cette transition restent à déterminer. De plus, ces tumeurs présentent de très nombreuses altérations moléculaires permettant d'envisager de nouvelles pistes de traitements ciblés notamment les anti-MET. Enfin, nous montrons l'implication du système immunitaire avec une infiltration importante de lymphocytes T CD8+, de macrophages CD163+ et une forte expression de PD-L1 ce qui ouvre de nouvelles perspectives de recherche et de traitements innovants. / Sarcomatoid carcinomas are a rare subtype of non-small cell lung cancer (NSCLC). Prognostic seems less favourable than other subtypes of NSCLC. Our team works to determine molecular characteristics of these tumors. In this work, we demonstrated that sarcomatoid carcinomas are chemoresistant to platinum based regimen in vitro and in vivo (primary cell lines) compared to other NSCLC. We demonstrated that this tumors share immunohistchemical, moleculary similarities with NSCLC validating the WHO classification. It is possible that these tumors came from cancer stem cell or underwent an epithelial-mesenchymal transition. Specificities of this transition remained undefined. Moreover these tumors presented a lot of molecular alterations allowing to investigate targeted therapies such as MET inhibitors. At last, we shows the implication of the immune system, the strong infiltration of TCD8+ lymphcoytes CD163+ macrophages and the expression of PD-L1, allowing to hope new perspective of research, innovative treatment.

Les cancers de l’ovaire représentent la première cause de mortalité due aux cancers gynécologiques dans les pays développés. La plupart de ces cancers sont diagnostiqués à des stades tardifs quand les cellules cancéreuses ovariennes ont disséminé et colonisé les parois de la cavité abdominale. En conséquence, ces cancers sont associés à un sombre pronostic.Plus d’un tiers des patientes présentent une accumulation de liquide d’ascite au moment du diagnostic. L’ascite est un fluide exsudatif ayant une composante cellulaire et également une composante liquide acellulaire, constituant un réservoir dynamique de molécules bioactives. Malgré une réponse efficace aux traitements standards, les taux de récidive de cette pathologie restent élevés. L’acquisition d’une chimiorésistance et le mode de propagation atypique des cellules cancéreuses sont deux éléments importants impliqués dans la récidive des cancers ovariens.Le rôle de l’ascite et plus particulièrement de la composante matricielle ascitique, dans le processus de dissémination et dans la chimiorésistance des cellules cancéreuses ovariennes reste peu étudié et constitue le cœur de ce travail de thèse.L’objectif des travaux a été d’étudier l’influence de l’ascite et de deux glycoprotéines matricielles purifiées à partir d’échantillons d’ascites sur les comportements cellulaires propices à la dissémination et à la récidive des cancers ovariens. De plus, l’influence de l’ascite sur la réponse des cellules aux traitements à base de platine a également été recherchée et estimée.L’étude démontre que l’ascite est un microenvironnement propice à la dissémination des cellules cancéreuses ovariennes et que la fibronectine et la vitronectine ascitiques ainsi que leurs récepteurs d’adhérence spécifiques sont des éléments qui participent à la régulation de cette dissémination. L’ascite exerce également un effet protecteur contre l’effet cytotoxique des agents chimiothérapeutiques.Ces résultats mettent en perspectives l’intérêt potentiel de la fibronectine et de la vitronectine ascitiques comme outils diagnostiques et/ou cibles thérapeutiques des cancers ovariens et nous engagent à approfondir l’étude de ces deux molécules et de leurs conséquences sur la progression de la maladie. / Ovarian cancers are the leading cause of death among gynaecological cancers in western countries. Most of these cancers are diagnosed at a late stage, when ovarian cancer cells have spread and colonized the walls of the abdominal cavity. Therefore, these cancers are associated to a poor prognosis.More than one third of the patients show an accumulation of ascites at the time of the diagnosis. Ascites are exudative fluids composed of a cellular and also an acellular fraction. In fact, ascites constitute a dynamic reservoir of bioactive molecules. Even if the response of ovarian cancers to the current first-line therapy, that consit in debulking surgery followed by chemotherapy, is satisfactory, the rate of recurrence remains important. The gain of a chemoresistance and the atypical widespread of cancer cells are two important factors involved in the recurence of the ovarian cancers.The role of ascites and more particularly, of the ascitic matrix componants on the dissemination process and on the chemoresitance of the ovarian cancer cells remain poorly studied and is the aim of this work.The objective of this study was to investiguate the influence of ascites and of two matrix glycoproteins purified from samples of ascites i) on the cells behavior convenient to the dissemination and the recurrence of the ovarian cancers and ii) on the response of cells to therapeutics treatments with platinum.This study suggests that ascites are a permissive microenvironment to the dissemination of ovarian cancer cells and that ascitic fibronectin and vitronectin as well as their specific receptors are actors which participate to the regulation of this dissemination. Ascites also protect ovarian cancer cells against the cytotoxicity of chemotherapeutic drugs.These results illustrate the potential interest of ascites derived fibronectin and vitronectin as diagnosis tools and/or therapeutic targets for ovarian cancers and encourage us to deepen the study of these two molecules and their consequences in the progress of the disease.

Le récepteur du facteur de croissance épidermique (EGFR) est une cible rationnelle pour les traitements anticancéreux des carcinomes épidermoïdes (CE). Cependant, seule une petite fraction de patients présente des avantages cliniques. Afin de comprendre l’échec de ces thérapies, j’ai étudié la voie de signalisation de l’EGFR en présence de fibroblastes associés aux carcinomes (FAC), principales cellules non malignes au sein des tumeurs. J'ai démontré que dans les CE, la voie de signalisation de l’EGFR coopère avec la rigidité de la matrice extracellulaire (MEC) induite par les FAC. Par la suite, j'ai cherché à résoudre les voies moléculaires qui sous-tendent cette coopération afin d'identifier de nouvelles cibles pharmaceutiques. Grâce à un criblage d'inhibiteurs pharmacologiques, j’ai identifié le vérapamil et le diltiazem, bloqueurs des canaux calcique CaV1, comme étant de puissants inhibiteurs de l'invasion des CE. Au niveau moléculaire, j'ai révélé que la rigidité de la MEC dérivée de la tumeur et la signalisation de l'EGFR déclenchent l'augmentation du calcium intracellulaire par le canal CaV1.1 dans les CE. Le blocage de l'activité de ces canaux inhibe l’invasion et la prolifération des cellules tumorale in vitro. Plus important encore, je démontre une forte réduction du développement des tumeurs dans deux modèles in vivo, à la fois dans un modèle de xénogreffe de cellules dérivées de patient atteint de carcinome de la tête et du cou, et dans un modèle CE cutané chez la souris. Par conséquent, je suggère une réaffectation du vérapamil et du diltiazem en tant qu’agents anticancéreux. / Epidermal growth factor receptor (EGFR) is a rational target for squamous cell carcinoma (SCC) anticancer therapies, nevertheless; only a subset of patients shows clinical benefits. I demonstrated a cooperation between EGFR signaling and extracellular matrix (ECM) stiffness that could explain this phenomenon. I sought to resolve the molecular pathway underlying this cooperation in SCC proliferation and expansion in order to identify new pharmaceutical targets. Screening of pharmacological inhibitors, in an in vitro 3-D assay, identified verapamil and diltiazem, FDA approved L-type calcium channels inhibitors, as potent blockers of SCC invasion. Mechanistically, I revealed that tumor-derived ECM stiffness and EGFR signaling trigger increased of intracellular calcium through the L-type CaV1.1 channel in SCC. Blocking L-type calcium channels activity resulted in reduced SCC cells invasion and proliferation in vitro. More importantly, I also demonstrate a strong reduction in tumor development in two in vivo models, both head and neck patient derived xenograft and skin SCC mice model. Consequently, I suggest a repurpose of verapamil and diltiazem to anti-cancer agents.

La transition épithélio-Mésenchymateuse (TEM) est un processus de plasticité cellulaire qui existe dans le développement embryonnaire et qui permet la formation des tissus et organes. Dans la cancérogénèse, ce processus est réactivé par des facteurs de transcription dont l’action implique très probablement un remodelage de la chromatine. La cartographie exacte de ces changements épigénétiques est peu connue à l’échelle du génome entier, même si il y a eu quelques études antérieures explorant les changements de quelques loci de façon bien ciblée. Ce mémoire traite du remodelage épigénétique médié par le facteur de transcription Twist1 dans un modèle de lignée mammaire immortalisée. L’architecture de ce remodelage a été cartographiée grâce à l’utilisation des techniques de haut-Débit pour analyser la méthylation de l’ADN (DREAM) et les modifications des histones (ChIPseq). Nos résultats montrent un changement majeur du méthylome pendant la TEM avec une hyperméthylation focale et une hypométhylation globale des corps des gènes prédominant au niveau des « domaines partiellement méthylés »; ces domaines sont déjà connus dans le développement pour gagner de façon concomitante à leur hypométhylation des marques d’histone répressives. Nous avons aussi observé un remodelage des domaines de l’histone répressive H3K27me3 avec une réduction de leur taille, et surtout le quasi doublement du nombre de gènes bivalents qui accompagne la transition. Le couplage de la méthylation de l’ADN avec le profil des microRNA nous a permis d’identifier le miR-203 comme l’unique microRNA régulé par méthylation de l’ADN durant la TEM; nous avons aussi montré que l’extinction épigénétique du miR-203 est requise pour la TEM et l’acquistion des propriétés de cellules souches. Enfin, nous avons réalisé une caractérisation génétique et/ou épigénétique de deux cancers rares, les carcinomes fibrolamellaires du foie et les carcinomes du rein à translocation. Pour les carcinomes fibrolamellaires du foie, nous avons décrit la nature endocrine de cette tumeur et établi une signature épigénétique basée sur la méthylation de l’ADN pouvant servir à différencier les formes histologiques appelées « pures » des formes « mixtes ». Pour les cancers du rein à translocation, nous avons montré les bases génétiques et épigénétiques de la différence entre les formes pédiatriques et adultes, avec la découverte fréquente du gain du bras chromosomique 17q dans les formes adultes. Nous avons aussi identifié une mutation récurrente dans le gène qui remodèle la chromatine INO80D appartenant à la famille INO80. En conclusion, ce travail explore le rôle de l’étude de l’épigénome pour comprendre la reprogrammation pendant les processus physiologiques comme la TEM d’une part et le cancer d’autre part. / The epithelial-Mesenchymal transition (EMT) is a process of cellular plasticity that exists in embryonic development and which allows the formation of tissues and organs. In carcinogenesis, the process is reactivated by transcription factors whose action probably involves chromatin remodeling. The exact mapping of these epigenetic changes is poorly understood genome-Wide, although there have been some previous studies exploring changes in so few well-Targeted loci. This thesis deals with the epigenetic remodeling mediated by the transcription factor Twist1 in a model of human mammary immortalized cell line. The architecture of this remodeling has been mapped through the use of high-Throughput techniques to analyze DNA methylation (DREAM) and histone modifications (ChIPseq). Our results suggest a major change in the EMT methylome with focal hypermethylation and gene body hypomethylation predominantly within "partially methylated domains"; these areas are already known in development to gain repressive histone marks concomitantly with DNA hypomethylation. We also observed landscape remodeling of repressive histone mark H3K27me3 with a reduction in domains size, and especially the almost doubling of the number of bivalent genes. The coupling of DNA methylation with the profile of microRNA has allowed us to identify miR-203 as single microRNA regulated by DNA methylation during EMT; we have also shown that epigenetic suppression of miR-203 is both required for EMT and acquisition of stem cell properties. Finally, we performed a genetic and/or epigenetic characterization of two rare cancers, named fibrolamellar hepatocellular carcinomas and translocation renal cell carcinomas. In fibrolamellar hepatocellular carcinoma, we described the endocrine nature of this tumor and established a signature based on DNA methylation which can be used to distinguish histological forms called "pure" from "mixed" fibrolamellar hepatocellular carcinomas. Regarding translocation renal cell carcinomas, we established the genetic and epigenetic basis of differences between pediatric and adult forms, characterized by frequent gain of 17q gain chromosomal arm in adults. We also identified recurrent mutations in the chromatin remodeling gene INO80D which belongs to INO80 family. In conclusion, this work explores the impact of analyzing the epigenome to understand reprogramming during physiological processes such as EMT and cancer.

No description available.