Thesis (Ph. D. in Cancer Biology)--Vanderbilt University, Aug. 2007. / Title from title screen. Includes bibliographical references.

Os insulinomas são os mais comuns neoplasmas endócrinos pancreáticos, constituindo cerca de 17% de todos os tumores neuroendócrinos do trato digestivo. São tumores raros, que tem, como principal manifestação clínica, a hipoglicemia, a qual é ocasionada por secreção exagerada de insulina pelo tumor. Devido ao fato de serem tumores raros, o conhecimento das mudanças genéticas associadas à iniciação e progressão desses tumores é muito limitado. Em função disto, o objetivo deste trabalho é a identificação de genes diferencialmente expressos em insulinomas benignos humanos, visando o melhor entendimento dos mecanismos moleculares do processo tumorigênico dos insulinomas e a descoberta de novos alvos moleculares para terapia. Utilizando-se a plataforma de \"bioarrays\" CodeLink foram identificados 354 genes mais expressos nos insulinomas benignos, sendo que 16% estavam envolvidos em proliferação. Dentre estes genes foram escolhidos 6 genes para validação por \"Real-Time PCR\", onde os genes SPARCL1, PRSS11 STAT4, ECRG4, ASCL1 confirmaram sua expressão diferencial nos tumores, porém a diferença do gene IGFALS não foi estatisticamente significativa. Através da técnica \"Representational Difference Analysis\", isolou-se o clone FLJ13072, como super-expresso nos insulinomas benignos quando comparado à ilhotas normais, sendo que a seqüência protéica putativa deste gene apresenta um domínio conservado de helicase, podendo estar envolvido em eventos de transcrição, tradução, reparo de DNA e remodelamento de cromatina. Uma das dificuldades encontradas no estudo dos insulinomas é a falta de linhagens celulares humanas. Por esta razão, iniciou-se o estabelecimento de culturas primárias e precoces de insulinomas humanos visando sua utilização como modelos celulares para futuros estudos funcionais dos genes identificados. / Insulinomas are the most common pancreatic endocrine neoplasms, comprising around 17% of all neuroendocrine tumors of the digestive tract. These rare tumors have hypoglycemia as the main clinical manifestation, caused by over secretion of insulin by the tumor. Based on that, the objective of this work is the identification of differentially expressed genes in human benign insulinomas, aiming at the better understanding of the molecular mechanisms of their tumorigenic process and the discovery of new molecular targets for therapeutics. Using the CodeLink bioarrays platform (GE Healthcare) 354 genes upregulated in human benign insulinomas were identified, among which, 16% are involved in cell proliferation. From these genes, 6 were chosen for validation by Real Time PCR, where SPARCL1, PRSS11, STAT4, ECRG4 and ASCL1 were shown to be upregulated in all benign tumors, however the expression difference of IGFALS gene were not statistically significant. Using the RDA (Representational Difference Analysis) methodology, the unknown gene FLJ13072 was shown to be upregulated in benign isulinomas when compared to normal pancreatic islets. The putative protein product from this gene has an helicase domain, being possibly involved in processes like transcription, translation, DNA repair and chromatin remodeling. An important drawback for the study of insulinomas is the lack of human cell lines. Because of that, the establishment of early primary cultures of human insulinomas was initiated, aiming at its use as a cell model for future functional studies of the genes identified.

Introdução: Os tumores carcinóides broncopulmonares típicos são proliferações malignas neuroendócrinas. Até bem pouco tempo eram consideradas como adenomas, isto é, tumores benignos. Porém com o avanço dos estudos anatomopatológicos, foi identificada a sua face maligna, pois apresenta as principais características das neoplasias malignas, quais sejam: metástase e invasão tecidual local. Além das metástases, estes tumores são capazes de produzir outra entidade ainda pouco estudada e conhecida que é a micrometástase. Estas correspondem a metástases menores que 2mm de diâmetro, que podem ou não se desenvolver, causando recidiva tumoral. Por sua vez as micrometástases são divididas em grupos de células tumorais, com diâmetro de 0,2 a 2mm e células tumorais isoladas, com diâmetro menor do que 0,2 mm. A literatura nos mostra que a incidência de micrometástase varia entre 10 a 90% dos pacientes em diversos tumores estudados. No caso dos carcinóides típicos temos pouca informação a respeito, sendo que a literatura nos mostra que a micrometástase em tumores carcinóides é considerada com fator de pior prognóstico. Porém não é o que observamos clinicamente, uma vez que temos o seguimento de inúmeros pacientes por mais de 10 anos, sem a recidiva tumoral em linfonodos mediastinais (seguimento clínicoradiológico). Objetivos: Verificar a presença de micrometástases em suas diversas formas, em pacientes portadores de carcinóide típico broncopulmonar, e verificar a possibilidade da predição do risco individual destas micrometástases em função de variáveis clínicas, anatomopatológicas e biomarcadores teciduais. Casuística e Métodos: Quarenta e nove pacientes portadores de carcinóide típico broncopulmonar com acompanhamento mínimo de 5 anos foram estudados. Todos foram submetidos a ressecção linfonodal por amostragem ou radical. As seguintes variáveis foram coletadas dos prontuários ou por entrevista: gênero, idade, localização do tumor em relação à carina (central ou periférico), diâmetro da lesão, comprometimento da margem cirúrgica, estadiamento TNM, ocorrência de metástases linfonodais, bem como quantidade de linfonodos acometidos por neoplasia em relação ao total dissecado, metástases à distância e tempo de sobrevivência. Os linfonodos foram analisados por coloração de hematoxilina-eosina e por imuno-histoquímica (Sinaptofisina e Cromogranina A) para pesquisa de micrometástase. Resultados: O grupo foi composto por 19 homens (38,8%) e 30 mulheres (61,2%). A idade média dos pacientes foi de 41,3 anos. Houve uma distribuição regular entre todos os lobos pulmonares acometidos. Em relação às vias aéreas, 78% dos tumores eram centrais e 22% eram periféricos. O diâmetro do maior eixo do tumor primário dos 49 pacientes variou de cinco a 80 milímetros, com mediana de 25 e intervalo interquartil 25 a 75% entre 16 e 35 milímetros. Em 54% dos casos foi realizada lobectomia pulmonar, 18% pneumonectomia, 12% bilobectomias e 16% procedimentos poupadores (segmentectomias, broncoplastias e nodulectomias). Em 12% dos casos houve comprometimento da margem cirúrgica. Em 42,8% dos casos houve imunomarcação por pelo menos um dos biomarcadores Sinaptofisina ou Cromogranina A para micrometástase. Em 18,4% dos casos foi diagnosticada macrometástase linfática, e em 1 caso ocorreu metástase hematogênica. Foram realizadas 4 baterias de testes avaliando os grupos sem e com metástases/micrometástases para se verificar a possibilidade de predição do risco individual de micrometástase. Conclusão: Foi possível encontrar micrometástases linfáticas utilizando imuno-histoquímica (Sinaptofisina e Cromogranina A). Não foi possível predizer o risco individual de micrometástases nos grupos estudados. Não houve diferença entre os grupos sem e com qualquer tipo de micrometástase. Não foi possível estabelecer correlação entre incidência de metástase e micrometástase nesta amostra populacional. / Introduction: The typical lung carcinoids are neuroendocrine tumors. Until short time ago they were considered adenomas, that is, benign tumors. Although, due to the anatomopathologic advances, it was identified its malignant behavior, once it presents the main characteristics of the malignant tumors: matastasis and local invasion. Beyond the metastasis, this tumor is able to produce another entity not yet well studied, the micrometastasis. This corresponds to metastasis shorter than 2mm in diameter that can or not develop and cause tumoral recurrence. The micrometastasis are divided in two groups: clusters, with diameter between 0,2 and 2mm, and isolated tumor cells, with diameter less than 0,2mm. The medical literature shows that the incidence of micrometastasis of different tumors has a wide variation, between 10 to 90%. In the case of the typical lung carcinoids few information is presented, and the presence of the micrometastasis worsen prognosis. On the other hand this is not what we usually see clinically, once the follow up of numerous patients of our casuistic for more than 10 years did not show the recurrence of the desease in the mediastinal lymphnodes. Objectives: Verify the presence of micrometastasis in its various forms in patients comited by lung carcinoid tumors and verify the possibility to predict the individual risk of micrometastasis from clinical and anatomopathological variables and tissue biomarkers. Casuistic and Methods: Forty nine patients with lung carcinoid tumors with follow up of at least 5 years were studied. All of them were submitted to mediastinal lymphnode dissection during the surgical procedure. The data collected was: age, gender, tumor location (central or peripherical), diameter, compromised surgical edge, TNM stage, lymphatic metastasis, hematogenic metastasis and survive. The lymphnodes were analised by Hematoxilin-Eosin and immunohistochemistry (Synaptophysin and Chromogranin A) in order to search for micrometastasis. Results: There were 19 men (38,8%) and 30 women (61,2%) with a mean age of 41,3 years. There was a regular distribution in all pulmonary lobes. There were 78% of central and 22% periferic tumors. The diameter varied between 0,5 to 80mm, with median in 25. In 54% of the cases was performed pulmonary lobectomy, in 18% pneumonectomy, in 12% bilobectomy and in 16% other procedures (bronchoplasty, wedge resection, nodulectomy). In 42,8% there was immunostaining with Synatophysin or Chromogranin A to micrometastasis. In 18,4% was diagnosed macrometastasis and in 1 case there was haematogenic metastasis. It was done 4 batteries of statistical tests to verify the possibility of prediction of the individual risk of micrometastasis. Conclusion: It was possible to find lymphatic micrometastasis using immunostaining with Synaptophysin and Chromogranin A. It was not possible to predict the individual risk of micrometastasis in the studied groups. There was no difference between the groups with or without micrometastasis. It was not possible to estabilish a correlation between the incidence of macro and micrometastasis in this population.

Introdução: Os tumores carcinóides broncopulmonares típicos são proliferações malignas neuroendócrinas. Até bem pouco tempo eram consideradas como adenomas, isto é, tumores benignos. Porém com o avanço dos estudos anatomopatológicos, foi identificada a sua face maligna, pois apresenta as principais características das neoplasias malignas, quais sejam: metástase e invasão tecidual local. Além das metástases, estes tumores são capazes de produzir outra entidade ainda pouco estudada e conhecida que é a micrometástase. Estas correspondem a metástases menores que 2mm de diâmetro, que podem ou não se desenvolver, causando recidiva tumoral. Por sua vez as micrometástases são divididas em grupos de células tumorais, com diâmetro de 0,2 a 2mm e células tumorais isoladas, com diâmetro menor do que 0,2 mm. A literatura nos mostra que a incidência de micrometástase varia entre 10 a 90% dos pacientes em diversos tumores estudados. No caso dos carcinóides típicos temos pouca informação a respeito, sendo que a literatura nos mostra que a micrometástase em tumores carcinóides é considerada com fator de pior prognóstico. Porém não é o que observamos clinicamente, uma vez que temos o seguimento de inúmeros pacientes por mais de 10 anos, sem a recidiva tumoral em linfonodos mediastinais (seguimento clínicoradiológico). Objetivos: Verificar a presença de micrometástases em suas diversas formas, em pacientes portadores de carcinóide típico broncopulmonar, e verificar a possibilidade da predição do risco individual destas micrometástases em função de variáveis clínicas, anatomopatológicas e biomarcadores teciduais. Casuística e Métodos: Quarenta e nove pacientes portadores de carcinóide típico broncopulmonar com acompanhamento mínimo de 5 anos foram estudados. Todos foram submetidos a ressecção linfonodal por amostragem ou radical. As seguintes variáveis foram coletadas dos prontuários ou por entrevista: gênero, idade, localização do tumor em relação à carina (central ou periférico), diâmetro da lesão, comprometimento da margem cirúrgica, estadiamento TNM, ocorrência de metástases linfonodais, bem como quantidade de linfonodos acometidos por neoplasia em relação ao total dissecado, metástases à distância e tempo de sobrevivência. Os linfonodos foram analisados por coloração de hematoxilina-eosina e por imuno-histoquímica (Sinaptofisina e Cromogranina A) para pesquisa de micrometástase. Resultados: O grupo foi composto por 19 homens (38,8%) e 30 mulheres (61,2%). A idade média dos pacientes foi de 41,3 anos. Houve uma distribuição regular entre todos os lobos pulmonares acometidos. Em relação às vias aéreas, 78% dos tumores eram centrais e 22% eram periféricos. O diâmetro do maior eixo do tumor primário dos 49 pacientes variou de cinco a 80 milímetros, com mediana de 25 e intervalo interquartil 25 a 75% entre 16 e 35 milímetros. Em 54% dos casos foi realizada lobectomia pulmonar, 18% pneumonectomia, 12% bilobectomias e 16% procedimentos poupadores (segmentectomias, broncoplastias e nodulectomias). Em 12% dos casos houve comprometimento da margem cirúrgica. Em 42,8% dos casos houve imunomarcação por pelo menos um dos biomarcadores Sinaptofisina ou Cromogranina A para micrometástase. Em 18,4% dos casos foi diagnosticada macrometástase linfática, e em 1 caso ocorreu metástase hematogênica. Foram realizadas 4 baterias de testes avaliando os grupos sem e com metástases/micrometástases para se verificar a possibilidade de predição do risco individual de micrometástase. Conclusão: Foi possível encontrar micrometástases linfáticas utilizando imuno-histoquímica (Sinaptofisina e Cromogranina A). Não foi possível predizer o risco individual de micrometástases nos grupos estudados. Não houve diferença entre os grupos sem e com qualquer tipo de micrometástase. Não foi possível estabelecer correlação entre incidência de metástase e micrometástase nesta amostra populacional. / Introduction: The typical lung carcinoids are neuroendocrine tumors. Until short time ago they were considered adenomas, that is, benign tumors. Although, due to the anatomopathologic advances, it was identified its malignant behavior, once it presents the main characteristics of the malignant tumors: matastasis and local invasion. Beyond the metastasis, this tumor is able to produce another entity not yet well studied, the micrometastasis. This corresponds to metastasis shorter than 2mm in diameter that can or not develop and cause tumoral recurrence. The micrometastasis are divided in two groups: clusters, with diameter between 0,2 and 2mm, and isolated tumor cells, with diameter less than 0,2mm. The medical literature shows that the incidence of micrometastasis of different tumors has a wide variation, between 10 to 90%. In the case of the typical lung carcinoids few information is presented, and the presence of the micrometastasis worsen prognosis. On the other hand this is not what we usually see clinically, once the follow up of numerous patients of our casuistic for more than 10 years did not show the recurrence of the desease in the mediastinal lymphnodes. Objectives: Verify the presence of micrometastasis in its various forms in patients comited by lung carcinoid tumors and verify the possibility to predict the individual risk of micrometastasis from clinical and anatomopathological variables and tissue biomarkers. Casuistic and Methods: Forty nine patients with lung carcinoid tumors with follow up of at least 5 years were studied. All of them were submitted to mediastinal lymphnode dissection during the surgical procedure. The data collected was: age, gender, tumor location (central or peripherical), diameter, compromised surgical edge, TNM stage, lymphatic metastasis, hematogenic metastasis and survive. The lymphnodes were analised by Hematoxilin-Eosin and immunohistochemistry (Synaptophysin and Chromogranin A) in order to search for micrometastasis. Results: There were 19 men (38,8%) and 30 women (61,2%) with a mean age of 41,3 years. There was a regular distribution in all pulmonary lobes. There were 78% of central and 22% periferic tumors. The diameter varied between 0,5 to 80mm, with median in 25. In 54% of the cases was performed pulmonary lobectomy, in 18% pneumonectomy, in 12% bilobectomy and in 16% other procedures (bronchoplasty, wedge resection, nodulectomy). In 42,8% there was immunostaining with Synatophysin or Chromogranin A to micrometastasis. In 18,4% was diagnosed macrometastasis and in 1 case there was haematogenic metastasis. It was done 4 batteries of statistical tests to verify the possibility of prediction of the individual risk of micrometastasis. Conclusion: It was possible to find lymphatic micrometastasis using immunostaining with Synaptophysin and Chromogranin A. It was not possible to predict the individual risk of micrometastasis in the studied groups. There was no difference between the groups with or without micrometastasis. It was not possible to estabilish a correlation between the incidence of macro and micrometastasis in this population.

Les GEPNETs (tumeurs neuroendocrines gastroentéropancréatiques), représentent le deuxième cancer digestif. L’octréotide (agoniste Sst2) contrôle efficacement leurs sécrétions et plus modérément la croissance cellulaire. Au cours de ma première partie de thèse, j’ai développé la culture primaire de GEPNETs humaines. Ceci m’a permis d’étudier l’effet antiprolifératif et antisécretoire du pasireotide (pan agoniste Sst) et de l’évérolimus (inhibiteur de la voie pi3 kinase Akt) en comparaison avec l’octréotide. J’ai mis en évidence un effet inhibiteur significatif et similaire de l’octréotide et du pasiréotide sur la viabilité cellulaire et la sécrétion de chromogranine A. Cependant, le trafic intracellulaire du Sst2 est diffèrent en présence de pasireotide. L’évérolimus inhibe la viabilité et la secretion cellulaire des GEPNETs de manière similaire aux SSA. Nous n’avons pas retrouvé d’additivité entre l’évérolimus et les SSA. Dans la deuxième partie de mon travail j'ai étudié l’effet de la surexpression du Sst2 dans les cellules de prolactinomes et NFPA humains. Apres surexpression de Sst2, l’octréotide est capable d’inhiber la sécrétion de PRL et la prolifération cellulaire des NFPAs. Cette surexpression n’améliore pas la sensibilité aux dopastatines (agonistes chimériques Sst2-D2DR) des prolactinomes alors qu’une amélioration est bien observée dans les NFPAs. En conclusion, la culture primaire des GEPNETs représente un bon modèle d’étude pharmacologique. La coopération Sst2–D2DR dans les NFPA est effective dans ce modèle et permettra l’étude des mécanismes mises en jeu par les dopastatines. / GEPNETs represent, in terms of prevalence, the second digestive cancer. Octreotide (Sst2 agonists) effectively control their secretion and partially cell growth. we developed a primary cell culture of human GEPNETs. Cell culture allowed the study of antisecretory and antiproliferative effect of pasireotide and everolimus, alone or in combination, as compared to octreotide, in 20 tumors. We highlighted a significant and similar maximal inhibitory effect of octreotide and Pasireotide either on cell viability or on chromogranin A secretion in all analyzed tumors. However, the intracellular trafficking of Sst2 was strikely different in the presence of pasireotide and octreotide. In all analyzed tumors, everolimus inhibits cell viability and secretion of GEPNETs similarly to SSA. We couldn’t reveal any additivity between everolimus and SSA in cell viability suppression.My second goal was to study the effect of overexpression of Sst2 by adenoviral transfer in cells of human prolactinomas and NFPA. In both cell types. Nevertheless, octreotide efficiently suppressed PRL secretion and cell proliferation (NFPA). Overexpression of Sst2 did not improve the efficcacy of dopastatines (chimeric Sst2 - D2DR agonists) on prolactin secretion in prolactinomas, but clealy improved suppression of cell proliferation in NFPA. These results suggest that dopostatin promotes a Sst2 D2DR cooperation in NFPA, but not in prolactinomas, where DRDR activation remains dominant. In conclusion, GEPNETs primary cell culture represents a good model for pharmacological In pituitary adenomas, Sst2 overexpression opens an interesting perspective for gene therapy in recurrent NFPA after surgery.

Neuroendocrine tumours generally show an overexpression of somatostatin receptors on their cell membranes, mainly subtype 2. This is taken advantage of in diagnosis and therapy by using synthetic somatostatin analogues that can be labelled with radionuclides to visualize and treat tumours with an overexpression of somatostatin receptors. The method traditionally used for visualization is somatostatin receptor scintigraphy (SRS) with 111In-DTPA-octreotide but this method is gradually being substituted by 68Ga-DOTATOC PET/CT. To evaluate patients for peptide receptor radionuclide therapy, it is mandatory for the patient to be examined by both methods. In the evaluation, the tumours are graded according to the Krenning scale on the images from the SRS. Patients with sufficient tumour uptake of somatostatin analogues are eligible for peptide receptor radionuclide therapy (PRRT). The aim of this study was to compare the tumour’s Krenning scores from SRS to the Krenning scores, quantitative indices and TNR-values from the 68Ga-DOTATOC PET/CT images. This was done to investigate if the Krenning scale could be applied to PET/CT enabling the patient to undergo only PET/CT for diagnosis and evaluation prior to PRRT. This study, including 28 patients, found no strong correlation between the Krenning scores from the SRS and the scores from 68Ga-DOTATOC PET/CT. However, a better correlation was shown between the Krenning scores from SRS and TNR-values where the quantitative indices SUVmax and SUVmean were divided with the SUVmean of the spleen. These findings could be worth exploring further in future studies, incorporating larger number of patients.

Neuroendocrine tumors (NETs), originally described as carcinoids, represent a rare and heterogeneous group of neoplasms associated with intensive secretion of hormones, bioactive peptides and amines. Most of the patients are diagnosed at a late stage of disease, often with liver metastases. Surgery remains the main treatment to control metastatic disease, but is not curative. Oncolytic virotherapy represents a promising approach to treat cancer and different strategies have been exploited to restrict viral replication to tumor cells. We developed an oncolytic adenovirus based on serotype 5, Ad5[CgA-E1A], where the chromogranin A (CgA) promoter controls expression of the E1A gene and thereby virus replication. We found that Ad5[CgA-E1A], selectively replicates in NET cells and it is able to suppress fast-growing human BON carcinoid tumors in nude mice. The activity of Ad5[CgA-E1A] was not completely blocked in liver cells. We further repressed virus replication in hepatocytes by targeting E1A with miR122, an miRNA specifically expressed in the liver. miRNAs bind to mRNA and induce its cleavage or translational blockage. By insertion of tandem repeats of miR122 target sequences in 3’UTR of E1A gene, we observed reduced E1A protein expression and replication arrest in miR122 expressing liver cells. The oncolytic potency of the miR122-targeted virus was not affected in NET cells. Since some NET and neuroblastoma cells express high levels of somatostatin receptors (SSTRs), we introduced in the virus fiber knob cyclic peptides, which contain four amino acids (FWKT) and mimic the binding site of somatostatin for SSTRs. The FWKT-modified Ad5 transduces midgut carcinoid cells from liver metastases about 3-4 times better than non-modified Ad5. Moreover, FWKT-modified Ad5 overcomes neutralization in an ex vivo human blood loop model to a greater extent than Ad5, indicating that the fiber knob modification may prolong the systemic circulation time. NETs represent a huge therapeutic challenge and novel diagnostic markers are needed for early detection and effective treatment of NETs. We have profiled primary tumors and liver metastases of ileocaceal NETs, using Affymetrix microarrays and advanced bioinformatics. We have identified six novel marker genes and show high similarity between primary lesions and liver metastases transcriptome by hierarchical clustering analysis.

Les cellules neuroendocrines sécrètent hormones et neuropeptides dans la circulation sanguine par un processus d’exocytose régulée par le calcium. Engendrant un apport de membrane important à la surface cellulaire, l'exocytose doit être suivie par un processus d’endocytose compensatrice afin de maintenir l’homéostasie cellulaire et assurer le recyclage des composés vésiculaires. La connaissance précise des mécanismes moléculaires qui régulent la sécrétion neuroendocrine est primordiale. En effet, de nombreux cancers neuroendocrines sont associés à un dysfonctionnement de la sécrétion hormonale. Bien que connus des cliniciens, les mécanismes cellulaires et moléculaires qui induisent de telles perturbations de sécrétion restent à ce jour inexplorés. Les travaux réalisés au laboratoire démontrent que la sécrétion hormonale dans les cellules neuroendocrines est contrôlée par RhoA, Rac1 et Cdc42, trois GTPases de la famille Rho. Néanmoins, les voies moléculaires contrôlant le cycle d’activation-inactivation de ces GTPases Rho lors de l’exocytose sont peu connues. Mon projet de thèse s’est articulé autour de deux axes principaux. Un premier objectif fut d’étudier, au cours de la sécrétion neuroendocrine, l’implication potentielle de l’oligophrénine-1, une protéine GAP capable d'inactiver certaines GTPases Rho. En utilisant les cellules chromaffines de la glande surrénale comme modèle cellulaire, j'ai découvert un double rôle de la protéine oligophrénine-1. En effet, en inactivant RhoA, l’oligophrénine-1 permettrait la mise en place du pore de fusion nécessaire à l'exocytose tandis que par le biais de son domaine BAR, elle contrôle l'endocytose compensatrice. Mon second objectif fut d’appréhender les bases cellulaires et moléculaires à l’origine du dysfonctionnement de la sécrétion dans les cancers neuroendocrines en utilisant les phéochromocytomes humains comme modèle expérimental. En combinant des analyses ampérométriques et protéomiques sur des tumeurs humaines, j'ai pu montrer que l'hypersécrétion catécholaminergique des phéochromocytomes est bien la conséquence d’une augmentation de l’activité sécrétrice. J'ai également pu identifier des acteurs protéiques, dont plusieurs modulateurs des GTPases de type Rho, qui pourraient être impliqués dans ces défauts de sécrétion. L’ensemble de mon projet de thèse m’a permis de mieux comprendre les mécanismes de régulation des GTPases Rho au cours de la sécrétion mais également de proposer les premières bases moléculaires et cellulaires abordant les perturbations de la sécrétion dans les tumeurs neuroendocrines. / Neuroendocrine cells release hormones and neuropeptides in the bloodstream through a calcium regulated exocytosis process. This process leads to an important increase of membrane at the cell surface which needs to be compensated through endocytosis in order to maintain cell homeostasis as well as the recycling of vesicular compounds. Many neuroendocrine cancers have been associated with a dysfunction in hormone secretion, urging toward a need to understand the molecular mechanisms which regulate neuroendocrine secretion. Even though these perturbations are known at a clinical level, the underlying cellular and molecular mechanism remains to be unraveled. Previous works in the team demonstrate that hormone secretion is regulated by RhoA, Rac1 and Cdc42, which are all GTPases of the Rho family. Nevertheless the molecular pathways which control the activation and inactivation cycle of these RhoGTPases during exocytosis remain unknown. My PhD project covered essentially two aspects. My first goal was to characterize the potential role of oligophrenin-1, a GAP protein which can inactivate Rho-GTPases, in neuroendocrine secretion. By using adrenal gland chromaffin cells as a cellular model, I have discovered a dual role for oligophrenin-1. Indeed, through RhoA inactivation, oligophrenin-1 allows the set up of a fusion pore, which is necessary for exocytosis, while controlling through the BAR domain the compensatory endocytosis. My second goal was to characterize the molecular and cellular basis which leads to a secretion dysfunction in neuroendocrine cancers by using human pheochromocytomas as an experimental model. By combining amperometric and proteomic analyses on human tumors, I was able to demonstrate that pheochromocytoma catecholaminergic secretion was indeed due to an increase in secretion activity. I could also identify major actors, including several Rho GTPase modulators, which could be implied in these secretion defects. All together, these approaches gave me a better understanding of RhoGTPase regulation during secretion but also an insight into the molecular and cellular basis of impaired secretion in neuroendocrine tumors.

Les néoplasmes neuroendocrines gastro-entéro-pancréatiques (NNE GEP) représentent un groupe de tumeurs rares se développant à partir des cellules neuroendocrines de l'organisme. L'arsenal thérapeutique disponible aujourd'hui pour les NNE GEP reste faible, même s'il s'est étoffé au cours de ces dix dernières années avec l'arrivée des thérapies ciblées (inhibiteurs de mTOR et de tyrosine-kinase). Cependant, ces traitements présentent des résistances qui conditionnent leur efficacité et aucun biomarqueur permettant de sélectionner les patients répondeurs à ces traitements ou d'anticiper le développement de résistances n'est connu. Identifier de nouvelles cibles thérapeutiques et comprendre les mécanismes de résistance est donc un enjeu dans le traitement des NNE GEP. Nos travaux montrent que les cellules de NNE GEP soumises à l'hypoxie ou la déplétion en glucose activent l'Unfolded Protein Response (UPR) et que la voie PERK favorise la survie cellulaire. De plus, la modulation de la réponse UPR (via des inhibiteurs ou inducteurs de l'UPR) diminue la croissance tumorale dans un modèle murin de dissémination métastatique de NNE GEP. Nous avons également découvert qu'un inhibiteur de mTOR, la rapamycine, permet d'activer préférentiellement la voie PERK de l'UPR, favorisant la survie des cellules traitées par la rapamycine. Ces résultats montrent l'intérêt de cibler la réponse UPR dans le traitement des NNE GEP. De plus, nous suggérons la mise en place d'un mécanisme de résistance aux inhibiteurs de mTOR impliquant la voie PERK. Si ces résultats se confirment in vivo et ex vivo, l'association d'un inhibiteur de mTOR et d'un inhibiteur de PERK pourrait palier aux phénomènes de résistance rencontrés avec les inhibiteurs de mTOR dans les NNE GEP / Gastroenteropancreatic neuroendocrine neoplasms (GEP NEN) are defined as rare neoplastic lesions developing from neuroendocrine cells. Therapeutic options available for GEP NEN are scarce, although targeted therapies such as mTOR or tyrosine-kinase inhibitors provide new opportunities. However, tumor cells develop resistances to these treatments, which reduce their effectiveness. To date, no biomarker is available to select patients responding to these treatments or to anticipate the development of resistances. Identifying new therapeutic targets and understanding mechanisms of resistance are therefore a relevant issue in the treatment of GEP NEN.We found that GEP NEN cells induce the Unfolded Protein Response (UPR) when subjected to hypoxia or glucose depletion, and that PERK pathway promotes cell survival. Modulation of the UPR thanks to UPR inhibitors or inducers decreases tumor growth in a murine model of metastatic dissemination of GEP NEN. Moreover, the mTOR inhibitor rapamycin preferentially induces PERK arm of the UPR, thereby promoting survival of rapamycin-treated cells. These results show the interest in targeting the UPR in the treatment of NNE GEP. In addition, we here suggest a new resistance mechanism to mTOR inhibitors involving PERK pathway. If these results are confirmed in vivo and ex vivo, the combination of mTOR inhibitor and PERK inhibitor could overcome mTOR inhibitors resistances in GEP NEN

Bien que rares, les tumeurs endocrines développées chez l'Homme demeurent problèmatiques. Une meilleure compréhension des mécanismes qui régulent leur croissance constitue un objectif essentiel pour identifier des cibles thérapeutiques nouvelles.Dans la première partie de cette thèse, nous avons étudié l'impact du microenvironnement tumoral (MeT), définit par l'ensemble des facteurs qui encerclent la niche tumorale primitive, sur la croissance des tumeurs endocrines digestives. In vitro, nous observons un effet prolifératif réciproque entre des fibroblastes, l'une des cellules pivots du MeT, et des lignées cellulaires humaines de tumeurs endocrines pancréatiques, tel qu'il est susceptible d'exister in situ. Dans une seconde partie, nous avons montré que le pegvisomant, un antagoniste du récepteur de l'hormone de croissance utilisé chez des patients atteint d'adénome hypophysaire somatotrope, n'a pas d'effet prolifératif in vitro sur les cellules somatotropes adénomateuses. / Although rare, endocrine tumors developed in Humans remain problematic, such as a better understanding of their regulatory mechanisms of growth represent a step forward to identify new therapeutical targets.In the first part of this thesis, we investigated the impact of the tumor microenvironment (TME), as defined by the factors surrounding the tumor primitive niche, on the growth of human digestive endocrine tumors. We, here, showed the occurrence of a reciprocal proliferation between human fibroblasts, a key cell within the TME, and human pancreatic neuroendocrine tumor cell lines, suggesting that human fibroblasts may constitue a new therapeutical target of interest in the TME of digestive endocrine tumors. In a second part, we showed that pegvisomant (PEG), a growth hormone receptor antagonist currently used in patients with GH-secreting pituitary adenoma, did not impact in vitro the proliferation rate of GH-secreting adenoma cells and therefore is suitable in patients with a persisting GH-secreting pituitary adenoma residue after surgery.