Le cycle cellulaire est finement régulé dans le temps et l'espace. Nous avons abordé les aspects dynamiques des interactions que la cycline A2 entretient avec ses partenaires Cdk1, Cdk2 et l'ubiquitine au cours du cycle cellulaire, dans des lignées cellulaires humaines. A cette fin, nous avons eu recours aux approches de FRET (Förster/fluorescence resonance energy transfer) et de FLIM (fluorescence lifetime imaging microscopy). Ceci nous a permis de montrer que les formes ubiquitinylées de la cycline A2 apparaissent principalement sous forme de foyers en prométaphase et se propagent ensuite à l'ensemble de la cellule. En outre, nous avons découvert que l'autophagie participe à la dégradation de cette cycline en mitose. Nous discutons les implications de ces observations quant à un rôle éventuel de la cycline A2 au moment de la formation de l'anneau de constriction, ainsi que de la participation de l'autophagie via cette cycline, dans la réponse aux dommages à l'ADN en mitose. / The cell cycle is finely regulated in time and space. We have studied the dynamical aspect of the interactions between cyclin A2 and its partners Cdk1, Cdk2 and ubiquitin during the cell cycle, in human cell lines. To this aim, we have used FRET (Förster/fluorescence resonance energy transfer) and FLIM (fluorescence lifetime imaging microscopy) techniques. We have thus shown that ubiquitylated forms of cyclin A2 are detected predominantly in foci in prometaphase, before spreading throughout the cell. Moreover, we have shown that autophagy contributes to cyclin A2 degradation in mitosis. We discuss the implications of these observations regarding a possible role of cyclin A2 when the cleavage furrow forms, and the participation of autophagy in DNA damage response in mitosis.

Orientador: Lúcia Regina Ribeiro / Banca: Daniel Araki Ribeiro / Banca: Maria Izabel Souza Camargo / Resumo: A Nutrigenômica é definida como o efeito da dieta na expressão gênica, e a extensão pela qual as diferenças genéticas entre os indivíduos influenciam a resposta a um padrão específico de dieta, à ingestão de alimentos funcionais e à suplementação de micronutrientes, em termos de um resultado para a saúde humana. A α-tomatina é um glicoalcalóide encontrado no tomate (Lycopersicon esculentum) que possui funções biológicas importantes como a redução dos níveis de colesterol LDL, inibição do crescimento de células cancerosas, estimulação do sistema imune e efeito antimetastático. O objetivo deste estudo foi avaliar a citotoxicidade da α-tomatina, os seus efeitos na proliferação celular, na indução de apoptose e expressão de RNAm dos genes APC, Ciclina A2, Catenina, CASP9, BAK, BAX e BCL-XL em células HT29. As células foram cultivadas em meio de cultura DMEM, suplementado com 10% de soro bovino fetal, e tratadas nas concentrações de 0,1, 1 e 10 μg/mL para o ensaio do MTT e proliferação celular. Na análise de apoptose morfológica utilizou-se as concentrações de 0,1, 1 e 2 μg/mL. Já para a avaliação da expressão gênica utilizou-se a concentração de 1 μg/mL. Após 12 horas de tratamento, o RNA das células foi extraído e a expressão dos genes foi avaliada através do método de PCR em tempo real. O gene GPDH foi utilizado como normalizador. A análise estatística foi realizada por ANOVA/Tukey para o ensaio do MTT. Os resultados do ensaio de cinética de proliferação celular, viabilidade celular e avaliação da indução de apoptose foram analisados estatisticamente através de ANOVA/Dunnet, e para a análise da expressão gênica utilizou-se o método de Pfaffl et al. (2002), através do cálculo estimado pelo método ΔΔCt. Os estudos experimentais indicaram que a α-tomatina foi citotóxica apenas na concentração de 10 μg/mL... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Nutrigenomics is defined as the effect of diet on gene expression, and the extent to which genetic differences between individuals influence the response to a specific pattern of diet, intake of functional foods and micronutrient supplementation, in terms of a result for human health. The α- tomatine is highlighted as a glycoalkaloid found in tomato (Lycopersicon esculentum) that has important biological functions such as reducing levels of LDL cholesterol, inhibit cancer cell growth, stimulation of the immune system and antimetastátic effect. In view of these considerations, the objective of this study was to evaluate the cytotoxicity of α-tomatine, their effects on cell proliferation, induction of apoptosis and morphological expression of mRNA of APC gene, Cyclin A2, β-Catenin, CASP9, BAK, BAX and BCL-XL in HT29 cells. The cells were grown in DMEM culture medium supplemented with 10% fetal bovine serum, and treated at concentrations of 0.1, 1 and 10μg/mL for the MTT assay and cell proliferation. In the morphological analysis of apoptosis, we used concentrations of 0.1, 1 and 2μg/mL. As for the evaluation of gene expression we used a concentration of 1 mg/mL. After 12 hours of treatment, the RNA from cells was extracted and gene expression was evaluated by the method of real-time PCR. The gene GPDH was used as normalizer. Statistical analysis was performed by ANOVA / Tukey test for MTT. The test results of kinetics of cell proliferation, cell viability and assessment of apoptosis were analyzed with ANOVA / Dunnet, and for analysis of gene expression we used the method of Pfaffl et al. (2002), by calculating estimated by ΔΔCt. Experimental studies suggested that α-tomatine was cytotoxic only at concentration of 10μg/mL. In the evaluation of cell proliferation were no significant differences in the treatments with α-tomatine, except that for the concentration... (Complete abstract click electronic access below) / Mestre

Made available in DSpace on 2014-06-11T19:22:58Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-02-17Bitstream added on 2014-06-13T18:08:59Z : No. of bitstreams: 1 ishii_pl_me_rcla.pdf: 341469 bytes, checksum: 30957c71a427ca667e0c86edb9d40228 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / A Nutrigenômica é definida como o efeito da dieta na expressão gênica, e a extensão pela qual as diferenças genéticas entre os indivíduos influenciam a resposta a um padrão específico de dieta, à ingestão de alimentos funcionais e à suplementação de micronutrientes, em termos de um resultado para a saúde humana. A α-tomatina é um glicoalcalóide encontrado no tomate (Lycopersicon esculentum) que possui funções biológicas importantes como a redução dos níveis de colesterol LDL, inibição do crescimento de células cancerosas, estimulação do sistema imune e efeito antimetastático. O objetivo deste estudo foi avaliar a citotoxicidade da α-tomatina, os seus efeitos na proliferação celular, na indução de apoptose e expressão de RNAm dos genes APC, Ciclina A2, Catenina, CASP9, BAK, BAX e BCL-XL em células HT29. As células foram cultivadas em meio de cultura DMEM, suplementado com 10% de soro bovino fetal, e tratadas nas concentrações de 0,1, 1 e 10 μg/mL para o ensaio do MTT e proliferação celular. Na análise de apoptose morfológica utilizou-se as concentrações de 0,1, 1 e 2 μg/mL. Já para a avaliação da expressão gênica utilizou-se a concentração de 1 μg/mL. Após 12 horas de tratamento, o RNA das células foi extraído e a expressão dos genes foi avaliada através do método de PCR em tempo real. O gene GPDH foi utilizado como normalizador. A análise estatística foi realizada por ANOVA/Tukey para o ensaio do MTT. Os resultados do ensaio de cinética de proliferação celular, viabilidade celular e avaliação da indução de apoptose foram analisados estatisticamente através de ANOVA/Dunnet, e para a análise da expressão gênica utilizou-se o método de Pfaffl et al. (2002), através do cálculo estimado pelo método ΔΔCt. Os estudos experimentais indicaram que a α-tomatina foi citotóxica apenas na concentração de 10 μg/mL... / Nutrigenomics is defined as the effect of diet on gene expression, and the extent to which genetic differences between individuals influence the response to a specific pattern of diet, intake of functional foods and micronutrient supplementation, in terms of a result for human health. The α- tomatine is highlighted as a glycoalkaloid found in tomato (Lycopersicon esculentum) that has important biological functions such as reducing levels of LDL cholesterol, inhibit cancer cell growth, stimulation of the immune system and antimetastátic effect. In view of these considerations, the objective of this study was to evaluate the cytotoxicity of α-tomatine, their effects on cell proliferation, induction of apoptosis and morphological expression of mRNA of APC gene, Cyclin A2, β-Catenin, CASP9, BAK, BAX and BCL-XL in HT29 cells. The cells were grown in DMEM culture medium supplemented with 10% fetal bovine serum, and treated at concentrations of 0.1, 1 and 10μg/mL for the MTT assay and cell proliferation. In the morphological analysis of apoptosis, we used concentrations of 0.1, 1 and 2μg/mL. As for the evaluation of gene expression we used a concentration of 1 mg/mL. After 12 hours of treatment, the RNA from cells was extracted and gene expression was evaluated by the method of real-time PCR. The gene GPDH was used as normalizer. Statistical analysis was performed by ANOVA / Tukey test for MTT. The test results of kinetics of cell proliferation, cell viability and assessment of apoptosis were analyzed with ANOVA / Dunnet, and for analysis of gene expression we used the method of Pfaffl et al. (2002), by calculating estimated by ΔΔCt. Experimental studies suggested that α-tomatine was cytotoxic only at concentration of 10μg/mL. In the evaluation of cell proliferation were no significant differences in the treatments with α-tomatine, except that for the concentration... (Complete abstract click electronic access below)

L'agressivité des cancers est souvent liée au pouvoir métastatique des cellules tumorales et la dissémination de ces dernières peut survenir suite à un phénomène appelé la transition épithéliomésenchymateuse. Une analyse de l'expression de la Cycline A2 conduite sur des échantillons humains de tumeurs primaires colorectales et de leurs métastases correspondantes révèle que cette protéine est moins abondante dans ces dernières. Le travail décrit dans cette thèse a permis de relier la Cycline A2 au remodelage du cytosquelette d'Actine dans les fibroblastes. Cette régulation requiert la localisation cytoplasmique de la molécule ainsi que son domaine N-terminal qui ne lie pas les CDKs. Nos expériences suggèrent que cette nouvelle activité est la conséquence d'une liaison directe entre la GTPase RhoA et la Cycline A2. La présence de cette dernière augmente l'activation de RhoA par sa GEF in vitro. L'utilisation de cellules épithéliales mammaires normales a permis l'identification d'un autre partenaire, RhoC. Dans ce contexte cellulaire, l'invalidation de la Cycline A2 diminue l'activation de RhoA et, renforce celle de RhoC ce qui conduit à une augmentation de l'invasion cellulaire en matrice de collagène. Ces cellules acquièrent aussi des propriétés mésenchymateuses caractéristiques de l'EMT, et ce phénotype est exacerbé par la présence de RasV12. Ce travail établit donc l'existence de nouvelles fonctions pour la Cycline A2 qui viennent compléter le tableau de régulation de la motilité par les protéines du cycle cellulaire et contribuent à une meilleure compréhension de son rôle dans le cancer. / Cancer aggressiveness is often associated with metastases occurrence and their dissemination can arise following an epithelial to mesenchymal transition (EMT). Cyclin A2 expression is lower in metastases relative to primary colon adenocarcinoma of matched human tumors. This manuscript describes new links between Cyclin A2 and Actin cytoskeleton remodeling in fibroblasts. This regulation requires a cytoplasmic localization of the protein and its N-terminal domain, which is unable to bind CDKs. This new Cyclin A2 activity appears to be mediated by its binding to RhoA. Accordingly, the activity of its GEF is potentiated when Cyclin A2 is present, in vitro. Furthermore, we used a normal mammary epithelial cell line and identified another Cyclin A2 partner, RhoC. Cyclin A2 depletion in this context leads to a reciprocal RhoGTPase activation where RhoA activation is impaired and that of RhoC is increased. Moreover, cell invasiveness is increased in a collagen matrix following Cyclin A2 knockdown in these cells. In addition, the epithelial cells acquire mesenchymal properties, which are exarcerbated by the expression of RasV12 and are characteristic of an EMT. Our work completes the network involving cell cycle proteins in motility. These novel functions of Cyclin A2 will hopefully help to understand the impact of its deregulation in cancer.

La cycline A2 est un régulateur essentiel du cycle cellulaire qui, en association avec des kinases dépendantes des cyclines (CDK) régule la réplication de l'ADN et l’entré des cellules en mitose. Dans de nombreux types de cancers humains, la cycline A2 a été considérée comme un facteur de prolifération contribuant à la cancérogenèse de par ses fonctions dans la régulation du cycle cellulaire. Récemment, la complexité des fonctions de cycline A2 a été révélée. Certaines études in vitro ont démontré que l'inactivation de la cycline A2 induit une augmentation de la motilité cellulaire et de l'invasion dans les fibroblastes consécutive à une activation défective de RhoA. De plus, il a été montré que l'inactivation de la cycline A2 induit la EMT par l’intermédiaire d’une augmentation de l'activité transcriptionnelle de la β-caténine, mais aussi via la voie TGFβ/Prefoldin. Ces études suggèrent que des niveaux réduits de cycline A2 sont liés à une invasion accrue et à l’apparition de métastases dans certains types de cancer. A l’aide d’un modèle de souris mutante pour la cycline A2, une étude récente a établi une fonction de cette dernière, indépendante des CDK, dans la réparation des cassures double brin de l'ADN et a montré que la perte de la cycline A2 favorise l’apparition de cancers de la peau et du poumon. L’ensemble de ces études met en évidence l’existence de multiples fonctions pour la cycline A2. Mon travail de thèse a consisté à explorer le rôle de la cycline A2 dans l'homéostasie du colon et le développement du Le cancer colorectal.Pour évaluer la valeur pronostique de la cycline A2 dans le CCR, nous avons analysé l'expression de la cycline A2 par IHC sur un grand nombre d'échantillons tumoraux dérivés de patients atteints de CCR de différents stades. Nous avons trouvé que les niveaux élevés de la cycline A2 sont corrélés avec un mauvais pronostic et une survie plus faible chez les patients atteints de CCR de stade I et II. Cependant, une diminution de l'expression de la cycline A2 a été détectée aux stades III et IV par comparaison aux biopsies de CCR de stade I et II. Il est tentant de proposer que le profil d'expression de la cycline A2 reflète ses rôles distincts au cours de la cancérogenèse du côlon, comme la prolifération cellulaire au stade précoce, lorsqu'elle est fortement exprimée, mais favorise l'invasion et l'agressivité à des stades plus avancés, lorsque ses niveaux d’expression sont réduits.En complément de cette étude clinique, nous avons généré des modèles murins porteurs d’une mutation constitutive ou inductible de la cycline A2 dans l’épithélium intestinal. Nous avons montré que la déplétion de la cycline A2 dans l'épithélium intestinal de la souris provoque une rupture de la crypte colique, une inflammation, une augmentation de la prolifération des cellules épithéliales et l’apparition de dysplasies de bas et haut grade, reconnues comme lésions précancéreuses dans le CCR. Ces observations suggèrent un rôle majeur pour la cycline A2 dans la régulation de l'homéostasie du côlon et l'initiation de la tumorigénèse. Une analyse plus poussée a révélé une proportion accrue de lésions au niveau de l'ADN et une activation aberrante de la β-caténine, anomalies couramment détectées chez les patients humains atteints de CCR et considérées comme les premières altérations de cette pathologie. En outre, nous avons détecté une expression élevée de NFkB et YAP1 chez les souris mutantes pour la cycline A2, voies qui jouent un rôle critique dans la régénération tissulaire et peuvent conduire la dédifférenciation des cellules épithéliales du côlon contribuant ainsi à la tumorigenèse. Finalement, les souris mutantes cycline A2 ont été soumises à un protocole de colite associé au cancer et ont développé une proportion accrue d'inflammation, mais aussi de dysplasies et d'adénocarcinomes, en taille et en nombre, suggérant que la perte de la cycline A2 participe à la carcinogenèse colorectale chez la souris. / Cyclin A2 is an essential cell cycle regulator required for accurate DNA replication and mitotic entry in association with cyclin-dependent kinases (CDKs). In multiple types of human cancers, cyclin A2 was considered as a proliferation driver contributing to carcinogenesis based on its function to promote cell cycle.Recently, the complexity of cyclin A2 functions has been revealed. Some in vitro studies demonstrated that cyclin A2 inactivation induces increased cell motility and invasiveness of mouse fibroblasts due to defective RhoA activation. Moreover, cyclin A2 inactivation has been shown to induce EMT through the upregulation of β-catenin transcriptional activity, but also via the TGFβ/Prefoldin pathway. These studies suggest that reduced levels of cyclin A2 are linked to increased invasiveness and metastasis in some cancer types. Using a cyclin A2 mutant mouse model, a recent study established the CDK-independent function of cyclin A2 in the repair of double-stranded DNA breaks and showed that loss of cyclin A2 promotes tumorigenesis in skin and lung due to deficient DSBs repair.Altogether, these studies highlight the multiple functions cyclin A2 can execute. The aim of my thesis was to explore the role of cyclin A2 in colon homeostasis and colorectal cancer development.To evaluate the prognostic value of cyclin A2 in CRC, we analyzed cyclin A2 expression by IHC on tumor samples derived from CRC patients of different stages. We found that high levels of cyclin A2 correlate with bad prognosis and lower survival in patients with stage I and II CRC. However, decreased cyclin A2 expression was detected in stage III and IV by comparison to stage I and II CRC biopsies. Complementary to the clinical study, we generated tissue-specific mutant mouse models bearing either a constitutive or inducible cyclin A2 deletion in the intestinal epithelium. We showed that depletion of cyclin A2 in mouse intestinal epithelium causes colonic crypt disruption, inflammation, increased proliferation of epithelial cells and occurrence of low- and high-grade dysplasia, recognized as precancerous lesions of CRC. These observations suggest a major role for cyclin A2 in the regulation of normal colon homeostasis and tumor initiation. Further analysis revealed an increased proportion of DNA damage and aberrant activation of β-catenin, commonly detected in human patients with CRC and which are considered as the first occurring alterations in this pathology. Furthermore, we detected elevated expression of NFkB and YAP1 in the colons of cyclin A2 mutant mice, pathways that have been previously shown to play critical roles for tissue regeneration after tissue damage and to drive dedifferentiation of colonic epithelial cells thus contributing to tumorigenesis. Finally, cyclin A2 mutant mice were subjected to a modified colitis-associated CRC model and developed increased proportion of inflammation, but also dysplasia and adenocarcinomas, in size and numbers, suggesting that loss of cyclin A2 contributes to inflammation-associated colorectal carcinogenesis in mice.

No description available.