L’immunologie anti-tumorale et l’immunothérapie ont connu dernièrement de grandes avancées avec la mise en évidence du processus d’immuno-surveillance et le développement de plusieurs approches vaccinales. Il n’en demeure pas moins que l’induction d’une réponse immunitaire anti-tumorale se traduit peu par l’éradication de la tumeur. Comme phénomène dynamique et interactif, la réponse cytotoxique anti-tumorale implique les effecteurs cytotoxiques et les cibles tumorales; pourtant, le microenvironnement tumoral et sa plasticité influent largement sur l’efficacité de celle-là. Avec l’appui de récentes données expérimentales, il apparaît crucial de prendre en compte la susceptibilité tumorale à la lyse par les effecteurs cytotoxiques anti-tumoraux, notamment les lymphocytes T cytotoxiques (CTLs), et plus particulièrement dans un contexte de plasticité cellulaire. Ainsi, le principal objectif de mes travaux de thèse est de saisir le rôle de la Transition Épithélio-Mésenchymateuse (EMT) dans la susceptibilité des cellules tumorales à la lyse par les CTLs dans des modèles cellulaires de cancer du sein. Nos résultats montrent que l’EMT est capable d’induire une diminution de la susceptibilité des cellules mésenchymateuses à la lyse spécifique. Elle engage de ce fait de multiples acteurs. Tout d’abord, dans les deux modèles d’étude, il s’avère que l’EMT est capable de réguler négativement l’expression de la molécule HLA-A2. Ensuite, dans le premier modèle expérimental, nous avons établi que l’EMT induit une altération de la signalisation au niveau de la synapse immunologique. De plus, le régulateur de l’autophagie, Becline 1, joue un rôle crucial dans l’induction de la diminution de la sensibilité à la lyse par les lymphocytes T-CD8+ suite à l’induction de l’EMT. Dans le deuxième modèle d’étude, le mécanisme mis en jeu par l’EMT pour réguler la susceptibilité des cellules mésenchymateuses à la lyse par les CTLs se manifeste dans l’induction du facteur de transcription inducteur des propriétés de cellules souches cancéreuses, le KLF4 ainsi que via la régulation négative de l’expression du miR-7. Ensemble, ces résultats élucident de nouveaux mécanismes d’échappement des cellules tumorales malignes à la lyse par les lymphocytes T-CD8+ suite à l’induction de l’EMT. Cette étude soutient ainsi l’importance du ciblage des facteurs de transcription inducteurs de l’EMT et responsables de la plasticité cellulaire afin de neutraliser leur fonction. Cela pourrait aider à construire une nouvelle stratégie pour mieux contrôler l’échappement des cellules tumorales invasives à la lyse spécifique et in fine pour garantir une immunothérapie plus efficace contre le cancer. / The anti-tumor immunology and immunotherapy have recently undergone major breakthroughs, with the identification of immune surveillance process and the development of several vaccine approaches. However, the fact remains that the induction of an antitumor immune response is still not effective enough. Certainly, the antitumor cytotoxic response is a dynamic and interactive phenomenon, involving cytotoxic effectors and tumor targets, but its effectiveness is considerably influenced by the tumor microenvironment and its plasticity. Recent studies support the importance of taking into account the tumor susceptibility to lysis by anti-tumor cytotoxic effectors, notably Cytotoxic T Lymphocytes (CTLs), especially in a context of cellular plasticity. On the grounds of these studies, this research aims at understanding the role of Epithelial to Mesenchymal Transition (EMT) in the susceptibility of tumor cells to CTLs mediated lysis in different models of breast cell carcinoma. Our results reveal that EMT is able to induce a decrease in the susceptibility of mesenchymal cells to specific lysis. It calls therefore multiple actors. First, in both study models, it turns out that the EMT is able to downregulate the expression of HLA-A2 molecule. Then, in the first experimental model, we show that EMT induces an alteration of signalling at the immunological synapse. Moreover, the regulator of autophagy, Beclin 1, plays a crucial role in the induction of reduced susceptibility to lysis by T-CD8+ lymphocytes following induction of EMT. In the second experimental model, we show that the mechanisms used by EMT to regulate the susceptibility of mesenchymal cells to lysis by CTLs involve the induction of the transcription factor inducing cancer stem cells properties, KLF4, as well as the downregulation of miR-7 expression. Together, these results shed light on new mechanisms used by malignant tumor cells to escape to lysis by T-CD8+ lymphocytes following the induction of EMT. Thus, this study advocates the importance of targeting transcription factors, which are inducers of EMT and responsible for cellular plasticity, in order to neutralize their function. These insights may prove useful for the development of new strategies aimed at better controlling the escape of invasive tumor cells to specific lysis, and ultimately ensuring a more effective immunotherapy against cancer.

Submitted by admin tede (tede@pucgoias.edu.br) on 2018-06-19T18:25:16Z No. of bitstreams: 1 DANIEL RODRIGUES DE BASTOS.pdf: 1922893 bytes, checksum: 51e3aa82ceb630f944c3c65627dcffaa (MD5) / Made available in DSpace on 2018-06-19T18:25:16Z (GMT). No. of bitstreams: 1 DANIEL RODRIGUES DE BASTOS.pdf: 1922893 bytes, checksum: 51e3aa82ceb630f944c3c65627dcffaa (MD5) Previous issue date: 2017-05-04 / Introduction: Breast cancer is the most frequent neoplasm among women worldwide and represents the leading cause of death in this population. Important biomarkers have been studied in order to better define the prognosis of patients affected by this cancer. MicroRNAs are small molecules of non-coding RNAs composed of 21 to 25 nucleotides that play an important role in the post-transcriptional regulation of several genes. Objective: The objective of this study was to evaluate the expression of microRNAs (miRNAs: hsa-miR-7 and hsa-miR-10b) and BRCA1 protein in breast cancer samples, as well as the possible associations between expression of these markers with clinicopathological and prognostic aspects. Method: The study included 92 cases of breast carcinoma from Hospital Araújo Jorge, Associação de Combate ao Câncer em Goiás. Formalin fixed paraphin embedded samples were used for the analisis. MicroRNA was extracted from the samples and used for cDNA synthesis. The cDNA samples were adjusted to the same concentration and submitted to quantitative real-time PCR (qRT-PCR). Samples were further evaluated by immunohistochemistry for BRCA1 expression. Results: From a group of 234 immunohistochemical records, 56 cases of non-triple-negative and 36 triple-negative breast carcinomas were selected. Five-year overall survival was significantly associated to triple negative phenotype (p = 0.044), advanced stages (p = 0.005), lymph node involvement (p = 0.038), presence of distant metastasis (p = 0, 0008) and absence of BRCA1 expression (p = 0.039). Significant associations were demonstrated between the absence of BRCA1 and the triple-negative phenotype (p = 0.0346), as well as the absence of estrogen receptor expression (p = 0.006) and absence of progesterone receptor expression (p = 0.0163). The analysis by qRTPCR demonstrated different levels of miR-10b and miR-7 expression in the tumors, with significant associations with triple-negative phenotype (p = 0.021, p = 0.042) and the absence of BRCA1 (p = 0.039, p = 0.006). The comparison between absence and presence of human epidermal growth factor receptor expression showed a significant difference for miR-7 (p = 0.031), and the expression of miR-10b in these cases was not statistically different (p = 0.926). Conclusion: Significant associations were demonstrated between the absence of BRCA1 and the triple-negative phenotype. Five-year overall survival was reduced for the triple-negative phenotype patients, clinical stages III and IV, the presence of lymph node metastasis, the presence of distant metastasis and the absence of BRCA1 expression. This study also demonstrated that hsa-miR-7 and hsa-miR-10b are significantly associated with the absence of BRCA1 expression and triple-negative phenotype, with poorer survival in these patient profiles. Studies with more cases and with cell lines should be performed in order to confirm the role of hsa-miR-7 and hsa-miR-10b in the modulation of BRCA1 expression. / Introdução: O câncer de mama é a neoplasia mais frequente entre as mulheres de todo o mundo e representa a principal causa de morte nesta população. Importantes biomarcadores têm sido estudados, a fim de definir melhor o prognóstico de pacientes acometidas por esta doença. Os microRNAs são pequenas moléculas de RNAs não codificantes, compostos por 21 a 25 nucleotídeos e desempenham importante papel na regulação pós-transcricional de diversos genes. Objetivo: O objetivo do estudo foi avaliar a expressão de microRNAs (miRNAs: hsa-miR-7 e hsamiR- 10b) e da proteína BRCA1 em amostras de câncer de mama, bem como as possíveis associações entre a expressão desses marcadores e os aspectos clinicopatológicos e prognósticos. Método: O estudo foi composto por 92 casos de carcinoma de mama, provenientes do Hospital Araújo Jorge, da Associação de Combate ao Câncer em Goiás. Foram utilizados fragmentos de tumores incluídos em parafina. A extração de microRNA das amostras foi realizada e o produto gerado foi utilizado para a síntese de cDNA. As amostras de cDNA foram ajustadas para igual concentração e submetidas à PCR quantitativa em tempo real (qRT-PCR). As amostras foram avaliadas ainda por meio de imuno-histoquímica para expressão de BRCA1. Resultados: Um total de 234 registros de imuno-histoquímica foi avaliado, resultando em 56 casos de carcinomas de mama apresentando fenótipo não triplonegativo e 36 com fenótipo triplo-negativo. A sobrevida das pacientes em função das características clinicopatológicas demonstrou associações com os casos triplonegativos (p=0,044), estádios mais avançados (p=0,005), acometimento linfonodal (p=0,038), presença de metástase à distância (p=0,0008) e ausência da expressão de BRCA1 (p=0,039). Associações significativas foram demonstradas entre a ausência de BRCA1 e o fenótipo triplo-negativo (p=0,0346), entre a ausência da expressão do receptor de estrógeno e ausência da expressão de BRCA1 (p=0,006), e entre o receptor de progesterona e a ausência da expressão de BRCA1 (p=0,0163). A análise por qRT-PCR demonstrou diferentes níveis de expressão de miR-10b e de miR-7, com associações significativas ao fenótipo triplo-negativo (p=0,021; p=0,042) e à ausência de BRCA1 (p=0,039; p=0,006). A comparação entre ausência e presença da expressão do receptor do fator de crescimento epidérmico humano demonstrou diferença significativa para miR-7 (p=0,031), sendo que a expressão de miR-10b nestes casos não foi estatisticamente diferente (p=0,926). Conclusão: Associações significativas foram demonstradas entre a ausência de BRCA1 e o fenótipo triplo-negativo. A sobrevida em cinco anos foi inversamente associada ao fenótipo triplo-negativo, aos estádios clínicos III e IV, à presença de metástase linfonodal, à presença de metástase à distância e à ausência da expressão de BRCA1. Este estudo demonstrou ainda que hsa-miR-7 e hsa-miR- 10b estão significativamente associados à ausência da expressão de BRCA1 e ao fenótipo triplo-negativo, sendo observada pior sobrevida nestes perfis de pacientes. Estudos com maior número de casos e com linhagens celulares devem ser realizados para constatar o papel de hsa-miR-7 e hsa-miR-10b na modulação da expressão de BRCA1.