L'hypertension artérielle pulmonaire (HTAP) idiopathique ou associée à une maladie sous-jacente est un trouble inexpliqué dont les formes graves, chez l'adulte comme le nouveau-né, restent mortels et pour lequel à ce jour, aucun traitement satisfaisant n'est disponible. Elle est caractérisée par une augmentation anormale de la pression artérielle pulmonaire (PAP) moyenne supérieur à 25 mmHg au repos et 30 mmHg à l'effort alors que chez un sujet sain elle est comprise entre 10 et 15 mmHg. L'hyperplasie des cellules musculaires lisses artérielle pulmonaire (CML-AP) est le principal déterminant du processus de remodelage vasculaire pulmonaire qui sous-tend l'hypertension artérielle pulmonaire.Il existe cependant des similitudes entre le cancer et l'hypertension artérielle pulmonaire. En effet, certains dysfonctionnements cellulaires et métaboliques sont communs aux deux maladies. En effet, des anomalies sont souvent retrouvées à la fois dans le cancer et dans les pathologies prolifératives, comme une mutation du gène codant pour le facteur de transcription p53, l'inactivation post-transcriptionnelle de p53 via l'inhibition de son interaction avec son régulateur négatif MDM2 (murine à double minute 2), l'augmentation de l'activité de la télomérase ainsi que la translocation de la sous-unité TERT vers la mitochondrie.Un moyen thérapeutique de choix dans le cancer ou autre pathologie proliférative est l'induction d'une sénescence cellulaire.Dans notre première étude, nous avons induit la sénescence des CML-AP en inhibant l'interaction p53-MDM2 en utilisant la Nutlin-3a, antagoniste spécifique et puissant de la liaison p53-MDM2, afin de limiter sa dégradation par le protéasome et ainsi augmenter son activité. Dans notre deuxième étude nous avons induit une sénescence des CML-AP en inhibant génétiquement ou pharmacologiquement la télomérase. Ces deux études ont montré que l'induction d'une sénescence cellulaire prévient et réverse partiellement l'HTAP dans différents modèles expérimentaux, en diminuant le nombre de CML-AP prolifératives et en augmentant le nombre de cellules sénescentes (p21-positives) sans induire davantage d'apoptose. Nous avons également confirmé l'implication de l'activité de la télomérase dans le développement de l'hypertension artérielle pulmonaire expérimentale ainsi que la translocation de la sous unité TERT dans la mitochondrie au cour de l'HTAP.La sénescence cellulaire semble donc être une cible thérapeutique de choix dans le traitement de l'hypertension artérielle pulmonaire. / Pulmonary artery hypertension (PH) occurring as an idiopathic condition or associated with an underlying disease is an unexplained disorder whose sever forms in adults and neonates are fatal and for which no satisfactory treatment is available. PH is characterized by an abnormal increase in pulmonary artery pressure (PAP) greater than 25 mmHg at rest and 30 mmHg during exercise while in a healthy person is between 10 and 15 mmHg. Hyperplasia of pulmonary artery smooth muscle cells (PA-SMCs) is the primary determinant of the pulmonary vessel remodeling process that underlies PH.However, similarities exist between cancer and PH. Indeed, some cellular and metabolic dysfunctions are common to both diseases. Abnormalities are often found in both cancer and proliferative disorders, such as an inactivating mutation in the gene encoding the transcription factor p53, a post-transcriptional p53 inactivation via interaction of the p53 protein with its negative regulator MDM2 (mouse double minute 2), increasing the telomerase activity and translocation of the TERT subunit to mitochondria.A selecting means in therapeutic cancer or other proliferative diseases is the induction of cellular senescence.In our first study, we induced CML-AP senescence by inhibiting the p53-MDM2 interaction using Nutlin-3a, a specific and potent antagonist of the p53-MDM2 binding, to limit its degradation by the proteasome and thus increase its activity. In our second study we induced CML-AP senescence by genetical or pharmacological inhibition of telomerase. Both studies showed that the induction of cellular senescence in PA-SMCs prevents and partially reverses PH in different experimental models, by reducing the number of proliferative CML-AP and increasing the number of (p21-positive) senescent cells without inducing more apoptosis. We also confirmed the involvement of telomerase activity and the translocation of the TERT subunit in the mitochondria during PH development.

Submitted by Erika Demachki (erikademachki@gmail.com) on 2017-01-11T17:21:26Z No. of bitstreams: 2 Tese - Flávio Silva de Carvalho - 2015.pdf: 7229360 bytes, checksum: c61e47d7d8698a2f433f115ce5265cb2 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2017-01-12T10:00:52Z (GMT) No. of bitstreams: 2 Tese - Flávio Silva de Carvalho - 2015.pdf: 7229360 bytes, checksum: c61e47d7d8698a2f433f115ce5265cb2 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2017-01-12T10:00:52Z (GMT). No. of bitstreams: 2 Tese - Flávio Silva de Carvalho - 2015.pdf: 7229360 bytes, checksum: c61e47d7d8698a2f433f115ce5265cb2 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2015-03-10 / Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq / Neoplasmas have been a major cause of death worldwide, with that the search for new candidates for prototypes of more effective anti-tumor drugs, safe and with fewer side effects when compared to those already available already in therapy, it is essential and fundamental importance. With this research goal, we developed the design, synthesis and pharmacological evaluation in order to obtain new candidate of heterocyclic antitumor drugs prototypes (46a-46Q, 48a-48s, 51a-51m, 50m-50a, 53b, 54b, 56b and 58b) and vectorized micronutrient (60) and nanostructures (63) drawn from LQFM 030 (37) prototypes, in that it (37) was obtained by simplifying molecular strategy nutlin from compound (34) . The route chosen to obtain the heterocyclic compounds (46Q-46a, 48a-48s, 51a-51m, 50m, 50a, 53b, 54b, 56b and 58b) resulted in yields ranging from 32-77%, where all synthesized compounds were elucidated through the use of Nuclear Magnetic Resonance dimensional and two-dimensional (NMR) and Infrared (IR). Two methodologies have been developed (A and B) for the synthesis of intermediate pyrazole compounds and formylated acid, wherein the first method was conventional and the second was by heating with microwaves, which have obtained gain in time and / or increasing the yield of these synthetic steps when comparing with the conventional method (A). The synthesized compounds were tested for cytotoxicity assays by MTT method on the cell line K562 leukemic ie, and B16F10 melanoma ie, where the cytotoxic profile was evaluated using the IC50 = 70 uM for K562 cells and IC 50 = 64, 7 uM to line B16F10, both using an exposure time of 48 hours. K562 cells for six compounds LQFM ie 88, 108, 165, 166, 168 and 169 showed higher cytotoxic profile when compared to the prototype LQFM030 compound (37). Regarding the B16F10 line, six other compounds LQFM ie 126, 127, 165, 166 and 169 showed a better cytotoxic profile when compared to the prototype compound LQFM030. Given the results, we can conclude that the planning strategy employed to obtain the study compounds was validated, and against the cytotoxic research profile of 46a-46Q, 48a-48s, 51a- 51m, 50m-50a, 53b, 54b , 56b and 58b, and have a perspective vectorization and nanostructuring of the best compounds evaluated for each type of cell line K562 and B16F10 ie, aiming at optimizing the antitumor activity / As neoplasias têm sido uma das principais causas de morte no mundo, com isso a busca de novos candidatos a protótipos de fármacos antitumorais mais efetivos, seguros e que apresentem menos efeitos colaterais, quando já comparados aos já disponíveis na terapêutica, é imprescindível e de fundamental importância. Com esse objetivo de pesquisa, foi desenvolvido o planejamento, síntese e avaliação farmacológica visando a obtenção de novos candidatos a protótipos de fármacos antitumorais heterocíclicos (46a-46q, 48a-48s, 51a-51m, 50a-50m, 53b, 54b, 56b e 58b), e vetorizados com micronutrientes (60) e nanoestruturados (63), desenhados a partir dos protótipos LQFM 030 (37), em que este (37) foi obtido por meio de estratégia de simplificação molecular a partir do composto Nutlin (34). A rota eleita para a obtenção dos compostos heterocíclicos (46a- 46q, 48a-48s, 51a-51m, 50a-50m, 53b, 54b, 56b e 58b) resultou em rendimentos que variaram entre 32-77 %, onde todos os compostos sintetizados foram elucidados através do emprego de Ressonância Magnética Nuclear Unidimensionais e Bidimensionais (RMN) e Infravermelho (IV). Foram desenvolvidas duas metodologias (A e B), para a síntese dos compostos intermediários pirazola, formilado e ácido, em que a primeira metodologia foi a convencional e a segunda foi por meio de aquecimento com micro-ondas, onde obtivemos ganho em tempo e/ou aumento no rendimento dessas etapas sintéticas ao serem comparadas com a metodologia convencional (A). Os compostos sintetizados foram submetidos aos ensaios de citotoxicidade pelo método MTT, sobre a linhagem celular K562 i.e. leucêmica, e B16F10 i.e. melanoma, onde o perfil citotóxico foi avaliado utilizando-se do IC50= 70 µM para a linhagem K562 e IC50=64,7 µM para a linhagem B16F10, ambos utilizando um tempo de exposição de 48h. Para a linhagem K562, seis compostos i.e. LQFM 88, 108, 165, 166, 168 e 169 apresentaram melhor perfil citotóxico, quando comparado ao composto protótipo LQFM030 (37). Com relação à linhagem B16F10, outros seis compostos i.e. LQFM 126, 127, 165, 166 e 169 demonstraram um melhor perfil citotóxico ao serem comparados ao composto protótipo LQFM030. Diante dos resultados obtidos, podemos concluir que a estratégia de planejamento empregada para a obtenção dos compostos de estudo foi validada, e face ao perfil de investigação citotóxico dos 46a-46q, 48a-48s, 51a-51m, 50a-50m, 53b, 54b, 56b e 58b, e têm-se como perspectiva a vetorização e nanoestruturação dos melhores compostos avaliados para cada tipo de linhagem celular i.e. K562 e B16F10, visando à otimização da atividade antitumoral

Submitted by Luciana Ferreira (lucgeral@gmail.com) on 2018-07-30T13:03:21Z No. of bitstreams: 2 Dissertação - Higor de Oliveira Ribeiro - 2018.pdf: 2288061 bytes, checksum: f75a8ba35bba846fdef29be7d37b6794 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Approved for entry into archive by Luciana Ferreira (lucgeral@gmail.com) on 2018-07-30T14:01:31Z (GMT) No. of bitstreams: 2 Dissertação - Higor de Oliveira Ribeiro - 2018.pdf: 2288061 bytes, checksum: f75a8ba35bba846fdef29be7d37b6794 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) / Made available in DSpace on 2018-07-30T14:01:31Z (GMT). No. of bitstreams: 2 Dissertação - Higor de Oliveira Ribeiro - 2018.pdf: 2288061 bytes, checksum: f75a8ba35bba846fdef29be7d37b6794 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2016-12-12 / Fundação de Amparo à Pesquisa do Estado de Goiás - FAPEG / The cancer encompasses a huge range of different types, requiring several therapeutic approaches for control and/or remission. An approach that has been considered quite promising is the inhibition of the formation of the MDM2/p53 complex. The formation of this complex hinders the triggering of the apoptotic process. The example of the Nutlins, inhibitors of this complex, have stood out as promising prototype drugs and are already in the clinical phase of investigation. The compound LQFM030 originated from the molecular simplification of Nutlin-1, which has already demonstrated antitumor activity against the Ehrlich Ascites Tumor model. In this work, we investigated the cytotoxic effect of compound LQFM030 against the K562 leukemic line, as well as some mechanisms of cytotoxicity. In the evaluation of cytotoxicity using the trypan blue exclusion method, we obtained an IC 50 value of 0.56 mM, similar to results obtained previously. For the other mechanics assays, IC25 (0.283 mM) of compound LQFM030 and 0.01 mM of compound Nutlin-3a were used for treatment for 24 hours. The compound Nutlin-3a was used as the standard for comparison. Morphological analyzes of K562 cells after treatment with compound LQFM030 suggest core fragmentation and chromatin condensation, indicating apoptosis triggered cell death, which was confirmed by flow cytometric analyzes. In cell cycle investigation, LQFM030 treated K562 cells demonstrated increased sub-G1 phase, phosphatidylserine exposure, decreased membrane potential, increased expression of TNF-R1 and caspase -3/7 caspase -9; However, there was a decrease in caspase -8. In turn, the treatment of leukemic cells with Nutlin-3a did not promote changes in the cell cycle, exposure of phosphatidylserine corroborating with data from the literature. In conclusion the studied compound, LQFM030, presented important biological activity with the capacity to induce death in leukemic cells by apoptotic mechanisms and interaction with MDM2 and MDX. The compound presented mechanisms in some aspects similarities to Nutlin-3a, but also showed different mechanisms evidencing its versatility in its biological performance. The discovery of new agents with multiple mechanisms is of great importance to increase the therapeutic armamentarium of cancer in a complementary way and, in addition, it can enhance the effectiveness of the treatment. / O câncer engloba uma variedade enorme de tipos diferentes, sendo necessárias diversas abordagens terapêuticas para controle e/ou remissão. Uma abordagem considerada bastante promissora é a inibição da formação do complexo MDM2/p53. A formação deste complexo dificulta o desencadeamento do processo apoptótico. Já se encontra em fase clínica de investigação um exemplo promissor inibidor deste complexo, os Nutlins. O composto LQFM030 foi originado a partir da simplificação molecular do Nutlin-1, o qual já demonstrou atividade antitumoral contra o modelo do Tumor Ascitico de Ehrlich. Neste trabalho, investigamos mecanismos de citotoxicidade do composto LQFM030 na linhagem leucêmica K562. Na avaliação da citotoxicidade utilizando o método de exclusão do azul de tripano, obtivemos um valor de IC50 de 0,56 mM, similar a resultados obtidos anteriormente. Para os demais ensaios mecanisticos, foi utilizado o IC25 (0,283 mM) do composto LQFM030 e 0,01 mM do composto Nutlin-3a, para tratamento por 24 horas. O composto Nutlin-3a foi utilizado como padrão de comparação. As análises morfológicas das células K562 após o tratamento com o composto LQFM030 demonstrou fragmentação do núcleo e a condensação da cromatina, indicando morte celular desencadeada por apoptose, onde juntamente com citometria de fluxo indicam um processo de morte celular. Na investigação do ciclo celular, as células K562 tratadas com LQFM030 demonstraram um aumento da fase sub-G1, exposição da fosfatidilserina, diminuição do potencial de membrana mitocondrial, aumento da expressão de TNF-R1, caspases -3/7 e caspase -9; contudo, houve diminuição da caspase -8. Por sua vez, o tratamento das células leucêmicas com o Nutlin-3a não promoveu alterações no ciclo celular, exposição de fosfatidilserina corroborando com dados da literatura. Em conclusão o composto estudado, LQFM030, apresentou atividade biológica importante com capacidade de induzir morte em células leucêmica por mecanismos apoptoticos e interação com MDM2 e MDMX. O composto apresentou mecanismos em alguns aspectos semelhanças ao Nutlin-3a, porém também mostrou mecanismos distintos evidenciando a sua versatilidade em sua atuação biológica. A descoberta de novos agentes com múltiplos mecanismos é de grande importância para aumentar o arsenal terapêutico de combate ao câncer de forma complementar e, podendo ainda potencializar eficácia do tratamento.

No description available.

Les intégrines sont des cibles thérapeutiques pertinentes en oncologie. Dans cette thèse, nous avons exploré le rôle de l’intégrine α5β1 dans les gliomes et les tumeurs du colon. Nous nous sommes particulièrement focalisés sur la voie intégrine-protéine p53 et son implication dans la résistance aux thérapies. Dans les gliomes, l’intégrine α5β1 est surexprimée dans les glioblastomes et participe à un mauvais pronostic de survie des patients. Nous avons démontré que l’intégrine confère une résistance à la chimiothérapie par le Temozolomide en régulant négativement l’activité de la protéine suppresseur de tumeurs p53. L’activation directe de p53 par un agent non-génotoxique, la Nutlin-3a, entraine une inhibition de l’expression de l’intégrine suggérant ainsi une réaction croisée négative entre intégrine α5β1 et p53. L’association de la Nutlin-3a avec un antagoniste de l’intégrine α5β1 entraine une mort des cellules par apoptose. Nous avons confirmé l’existence d’une réaction croisée négative entre intégrine α5β1 et protéine p53 dans les tumeurs du colon où l’intégrine représente également une cible thérapeutique. / Integrins seem to be attractive anti-cancer targets. In this work we investigated the role of integrin α5β1 in glioma brain tumors and colon cancer. We were particularly interested in the role of integrin α5β1/p53 pathway in resistance to therapy. We first focused on gliomas and found that α5β1 integrin was overexpressed in aggressive malignant glioma tumors. Moreover, we showed that α5β1 integrin upregulation was associated with a shorter patient survival. We also demonstrated that α5β1 integrin expression in glioblastomas participates to the resistance to the chemotherapeutic agent Temozolomide, through a negative regulation of the tumor suppressor p53. A direct p53-activation by the non-genotoxic agent Nutlin-3a down-regulated α5 integrin subunit and thus sensitized glioblastoma cells to Nutlin-3a. Furthermore, we demonstrated that the inhibition of α5β1 integrin with a concomitant p53-activation enhanced the effects of p53-based therapy. We also confirmed the existence of a negative cross-talk between α5β1 integrin and p53 in colon cancer.

The p53 tumour suppressor protein lies at the hub of a very complex network of cellular pathways including apoptosis, cell cycle arrest, DNA repair and cellular senescence. However, the mechanism of why and how p53 switches between apoptosis and cell cycle arrest, thereby determining a cell’s fate, remains a mystery to us. To enable us to investigate this ability of p53 to switch between cell cycle arrest and apoptosis, we developed a model which demonstrates similar p53 expression patterns but different functional outcomes. Treating cells with Cisplatin (a common chemotherapeutic drug) and Nutlin-3 (an MDM-2 inhibitor) results in similar high levels of p53 accumulation but different cellular responses. Cisplatin-treated cells undergo apoptosis while Nutlin-treated cells enter cell cycle arrest. Using this model, we explored the localization of p53 and in particular a C-terminal Ser 392 moiety in an attempt to identify how p53 is able to preferentially activate cell cycle arrest or apoptotic pathway.

MDM2 regulates p53 predominantly by promoting p53 ubiquitination. However, ubiquitination-independent mechanisms of MDM2 have also been implicated. Here we show that MDM2 inhibits p53 DNA binding activity in vitro and in vivo. MDM2 binding promotes p53 to adopt a mutant-like conformation, losing reactivity to antibody Pab1620, while exposing the Pab240 epitope. The acidic domain of MDM2 is required to induce p53 conformational change and inhibit p53 DNA binding. ARF binding to the MDM2 acidic domain restores p53 wild type conformation and rescues DNA binding activity. Furthermore, histone methyl transferase SUV39H1 binding to the MDM2 acidic domain also restores p53 wild type conformation and allows p53-MDM2-SUV39H1 complex to bind DNA. These results provide further evidence for an ubiquitination-independent mechanism of p53 regulation by MDM2, and reveal how MDM2-interacting repressors gain access to p53 target promoters and repress transcription. Furthermore, we show that the MDM2 inhibitor Nutlin cooperates with the proteasome inhibitor Bortezomib by stimulating p53 DNA binding and transcriptional activity, providing a rationale for combination therapy using proteasome and MDM2 inhibitors.

Le terme d’« hypertension artérielle pulmonaire » (HTAP) décrit une maladie vasculaire pulmonaire caractérisée par une augmentation progressive des pressions artérielles pulmonaires (PAP), définie par une PAP moyenne supérieure ou égale à 25 mmHg au repos et dont le principal symptôme est un essoufflement à l’effort. Un remodelage artériel pulmonaire intense conduisant à une obstruction des petits vaisseaux pulmonaires est responsable de la maladie. C’est une maladie rare mais néanmoins grave car pouvant aboutir à une insuffisance ventriculaire droite et entraîner le décès du patient.Le cadre général de notre étude est l’amélioration de la compréhension des mécanismes physiopathologiques de l’HTAP afin d’identifier de nouvelles cibles thérapeutiques potentielles. Nous nous sommes intéressés plus particulièrement au phénotype « pseudo-tumoral » des cellules musculaires lisses des artères pulmonaires (CML-AP) des patients atteints d’HTAP qui jouent un rôle primordial dans le remodelage vasculaire pulmonaire de l’HTAP et qui présentent des caractéristiques communes avec les cellules cancéreuses, notamment une hyper-prolifération, une résistance à l’apoptose, des désordres métaboliques et une instabilité génomique. Etant donné que la protéine p53, un des plus importants suppresseurs de tumeur, est largement décrite comme inactivée dans la plupart des cancers, nous avons émis l’hypothèse qu’elle pourrait également jouer un rôle important dans le développement de l’HTAP. Les résultats des études in vitro menées sur des CML-AP de patients atteints d'HTAP idiopathiques (HTAPi) versus des sujets contrôles semblent indiquer que la protéine p53 n’est pas altérée dans les CML-AP HTAPi. En effet, la séquence codante du gène TP53 ne présente pas de mutation dans les CML-AP HTAPi, les expressions génique et protéique de p53 (et de certaines de ses protéines cibles) ne semblent pas être différentes entre contrôles et HTAPi, ni à l’état basal ni en réponse à différents stress cellulaires inducteurs de p53 (étoposide et H2O2). Cependant, la régulation de p53 semble altérée puisque nous avons observé une augmentation du taux protéique de MDM2, principal régulateur de p53, dans les CML-AP HTAPi. Ce résultat peut être considéré comme une des caractéristiques « pseudo-tumorales » des CML-AP HTAPi mais également être un élément déterminant du mécanisme d’action de la Nutlin-3a, qui a montré des effets anti-prolifératifs accrus dans les CML-AP HTAPi.Dans des études in vivo menées chez le rat, la protéine p53 semble jouer un rôle dans l’initiation de la pathogénèse d’une HTAP. En effet, les taux protéiques pulmonaires de p53, de sa cible p21 et de son régulateur (mais également cible transcriptionnelle) MDM2 sont diminués lors de la première semaine dans un modèle d’induction d’HTAP par mono-injection de monocrotaline (MCT) chez le rat, au cours duquel la pathologie se développe à partir de la 2ème semaine. De plus, l’administration quotidienne à des rats d’un inhibiteur de l’activité transcriptionnelle de p53, le pifithrin-α (PFT), conduit au développement d’une HTAP en 14 jours, au même titre qu’une mono-injection de MCT, et aggrave l’HTAP induite par la MCT. Des effets pro-prolifératifs et anti-apoptotiques du PFT révélés sur des CML-AP indiquent que l’inhibition de l’activité transcriptionnelle de p53 est à l'origine d'une prolifération exagéree et une résistance à l'apoptose, deux composantes clés dans le remaniement vasculaire pulmonaire et le développement de l'HTAP.En conclusion, ces résultats mettent en évidence l’implication de l’inactivation de la voie de p53 lors de la phase initiatrice du développement de l’HTAP, alors qu’aux stades tardifs et sévères de la maladie, il semble il y avoir une normalisation de p53. En revanche, l’augmentation de l’expression de son principal régulateur MDM2 observée dans les CML-AP de patients HTAP semble être une cible thérapeutique potentiellement intéressante. / Pulmonary artery hypertension (PAH) is a severe pulmonary vascular disease characterized by a progressive increase of the pulmonary arterial pressure (PAP), defined by a mean PAP greater than or equal to 25 mmHg at rest. The main symptom is a shortness of breath. An intense pulmonary arterial remodeling that leads to an obstruction of the small pulmonary vessels is responsible of the disease. PAH is a rare but severe disease that develops into right ventricular cardiac failure leading to the patient's death.The general framework of our study was to improve the understanding of the pathophysiology of PAH in order to identify new potential therapeutic targets and improve the clinical management of patients. In particular, we were interested in the “cancer-like phenotype” of PAH patient pulmonary arterial smooth muscle cells (PA-SMCs). PA-SMCs play a key role in the pulmonary vascular remodeling of PAH. These cells share characteristics with cancerous cells, such as: exaggerated proliferation, apoptosis resistance, metabolic disorders and genomic instability. Owing to the growth-suppressive and pro-apoptotic functions of p53 protein and its inactivation largely described in cancer, we hypothesized that the p53 pathway could also be altered during PAH development in PA-SMCs.The results of in vitro studies on PA-SMCs of late stage patients with idiopathic PAH (iPAH) versus control patients suggest that the p53 protein nor pathway is not altered in iPAH PA-SMCs. Indeed, the coding sequence of the TP53 gene presented no mutations in iPAH PA-SMCs. Analysis of mRNA and protein levels of p53 and its target proteins showed no difference between controls and iPAH PA-SMCs, neither in a basal state or in response to various cellular stresses such as etoposide and H2O2. However, regulation of p53 may be altered in iPAH PA-SMCs as we observed an increase of the MDM2 (the main p53 regulator) protein level compared to control. This last result may be considered as a “cancer-like” characteristic of iPAH PA-SMCs and also be a determining factor in the mechanism of action of Nutlin-3a, which had more important anti-proliferative effects in iPAH PA-SMCs than in control cells.In vivo studies in rats revealed, however, that the p53 pathway may play a role in the initiation stage of PAH pathogenesis. Indeed, kinetics evaluation of p53 lung expression in the PAH model, induced by a single injection of monocrotaline (MCT), revealed a decrease in the p53 protein level during the first week, followed by a normalization by the second week. PAH symptoms are developed in MCT rats after two weeks. Similarly, the protein levels of p21, a p53 target, and MDM2, the major p53 regulator, and also a transcriptional target of p53, decreased during the first week in the MCT-PAH model. In addition, daily treatment in rats with an inhibitor of p53 transcriptional activity, pifithrin-α (PFT), led to the development of PAH in 14 days, similarly to MCT, and worsened the PAH induced by MCT. Pro-apoptotic and anti-proliferative effects of PFT on PA-SMCs indicate that inhibition of p53 transcriptional activity causes an excessive proliferation and an apoptosis resistance, which are two key components of the pulmonary vascular remodeling and development of human and experimental PAH.In conclusion, these results demonstrate the involvement of the p53 pathway inactivation in the initiation stage of PAH development, whereas in late and severe stages of disease, its role seems to be less implicated. In contrast, the increased expression of MDM2 observed in PA-SMCs of PAH patients may be a potential therapeutic target.

Triple-negative breast cancers (TNBCs) are highly refractive to current treatment strategies, and new multi-targeted treatments need to be elucidated. Combination therapy that includes targeting the murine double minute 2 (Mdm2) signaling axis offers a promising approach. Protein-protein interaction inhibitors such as Nutlin-3a block the binding of key signaling molecules such as p53, p73α, and E2F1 to the hydrophobic pocket of Mdm2 and can lead to activation of cell-death signaling pathways. Since clinical trials for TNBC are evaluating the DNA damaging agent carboplatin, the objective of this thesis was to evaluate the therapeutic potential and mechanism of action of combination carboplatin and Nutlin-3a to treat TNBC. In TNBC cell lines with a mutant p53 background, we determined if modulation of Mdm2 function in the context of carboplatin-mediated DNA damage resulted in a synergistic inhibition of cell growth. Several ratios of carboplatin:Nutlin-3a were strongly synergistic in increasing cell death, with combination indices of 0.5 and lower. Mechanistic studies indicated that drug sensitivity and Mdm2 expression were dependent on p73. Mdm2 localized to a larger degree in the chromatin fraction isolated from cells treated with the combination treatment consistent with observations by others that Mdm2 binds to the Mre11/Rad50/Nbs1 complex, inhibits the DNA damage response, and increases drug sensitivity. In vivo efficacy experiments were conducted in the TMD231 orthotopic mammary fat pad model in NOD.Cg-PrkdcscidIl2rgtm1Wjl/SzJ (NSG) mice. For assessment of baseline tumor burden and randomization, fluorescent imaging of E2-Crimson expressing TMD231 cells was performed. Following Nutlin-3a and carboplatin combination treatment, there was a statistically significant reduction in primary tumor volume as well as lung metastases with significantly increased probability of survival compared to Vehicle and single drug treatments (p<0.001). While there was a decrease in bone-marrow cellularity, this did not lead to bone-marrow aplasia, and body weights recovered to normal levels within 7 days post-treatment. The present studies demonstrate the promise of Mdm2 as a therapeutic target in combination with conventional therapy, increase our understanding of how to potentiate DNA damage in cancers, and may lead to new clinical therapies for triple-negative primary and metastatic breast cancer.

A key effect of human papillomavirus (HPV) infection is to disrupt the normal cell cycle in order to subvert the cellular DNA replication machinery. Morphologically, condylomata induced by high and low risk HPV types cannot be distinguished and many studies have shown that the pattern of viral gene expression is similar in condylomata caused by both high risk and low risk HPV types. Detailed morphological study of cell cycle protein expression has not previously been performed on condylomata infected with low risk HPV types. The findings presented suggest that the mechanisms employed by low risk HPV6 or HPV11 to subvert cellular functions in condylomata acuminata are similar to those employed by high risk HPVs, with the exception of cyclin D1 and p53 protein over-expression. The differences in p53 expression and cyclin D1 expression seen between high and low risk HPV infection, reflect the known differences between high and low risk types and are in agreement with the known differences between high risk and low risk E6 and E7 proteins. PHK transduction studies demonstrated HPV E6 and E7 induce changes in cell cycle protein expression and that there are differences in cell cycle abrogation between HPV6 and HPV16. Disruption of the p53-MDM2 interaction can lead to activation of the p53 pathway. HPV infected lesions almost always contain wild-type p53. The binding of HPV E6 to p53, and its subsequent targeting for degradation, prevents activation of the p53 pathway in HPV infected cells. Cells over expressing HPV genes were treated with Nutlin-3, a MDM2-small molecule antagonist. The findings presented suggest treatment with Nutlin-3 induces cell cycle arrest in cells expressing HPV16 E7 and HPV6 E6 and HPV6 E7. This suggests a potential role for Nutlin-3 in the treatment of HPV infected cells.