京都大学 / 新制・論文博士 / 博士(医学) / 乙第13572号 / 論医博第2298号 / 新制||医||1069(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 藤田 恭之, 教授 武藤 学, 教授 伊藤 貴浩 / 学位規則第4条第2項該当 / Doctor of Medical Science / Kyoto University / DFAM

Skeletal muscle atrophy is a common and often debilitating complication of diverse stresses including muscle disuse, fasting, aging, critical illness and many chronic illnesses. However, the pathogenesis of muscle atrophy is still poorly understood. The thesis herein describes my studies investigating the molecular mechanisms of skeletal muscle atrophy. Using mouse skeletal muscle and cultured skeletal myotubes as experimental systems, I discovered a novel stress-induced pathway in skeletal muscle that causes muscle atrophy. The pathway begins with stress-induced expression of ATF4, a basic leucine zipper (bZIP) transcription factor with an evolutionarily ancient role in cellular stress responses. I found that diverse stresses including fasting and muscle disuse increase expression of ATF4 in skeletal muscle. ATF4 then activates the growth arrest and DNA damage-inducible 45a (Gadd45a) gene, leading to increased expression of Gadd45a protein, an essential and inducible subunit of DNA demethylase complexes. Gadd45a localizes to skeletal myonuclei where it interacts with and stimulates demethylation of a specific region in the promoter of the cyclin dependent kinase inhibitor 1a (Cdkn1a) gene. By demethylating the Cdkn1a promoter, Gadd45a activates the Cdkn1a gene, leading to increased expression of Cdkn1a protein, also known as p21WAF1/CIP1. Cdkn1a stimulates protein breakdown (a critical pro-atrophy process) and inhibits anabolic signaling, protein synthesis and PGC-1α expression (processes that maintain healthy skeletal muscle and protect against atrophy). As a result, Cdkn1a causes skeletal muscle fibers to undergo atrophy. Importantly, interventions that reduce any one component of this pathway (ATF4, Gadd45a or Cdkn1a) reduce skeletal muscle atrophy during fasting, muscle disuse, and perhaps other skeletal muscle stresses such as illness and aging. Conversely, forced expression of any one component of this pathway is sufficient to cause skeletal muscle fiber atrophy in the absence of upstream stress. These data suggest the ATF4/Gadd45a/Cdkn1a pathway as a potential therapeutic target. Collectively, my studies demonstrate that the sequential, stress-induced expression of ATF4, Gadd45a and Cdkn1a is a critical process in the pathogenesis of skeletal muscle atrophy. This significantly advances our understanding of how muscle atrophy occurs and it opens up new avenues of investigation into the causes and treatment of muscle atrophy.

On note un taux élevé de résistance aux traitements dans la leucémie myéloïde aiguë (LMA). Cette résistance peut être associée aux altérations de TP53. Les « ubiquitin specific peptidases » (USP) sont impliquées dans plusieurs cancers mais leurs rôles ne sont pas élucidés dans les LMA. L’analyse de l’expression génique par RT-PCR quantitative de 21 USP et des gènes de l’axe USP7-MDM2-TP53-CDKN1A dans 111 échantillons de LMA a montré une dérégulation de USP44, USP1, USP28 et CDKN1A dans respectivement 72%, 44%, 25% et 42% des cas. CDKN1A, une cible importante de TP53, pourrait avoir un rôle dans la résistance au traitement. Nous avons développé un modèle expérimental pour évaluer la réponse des cellules leucémiques à la doxorubicine et au nutlin 3, un modulateur non génotoxique de TP53, selon l’expression initiale de CDKN1A. Ce travail préliminaire suggère que certains membres de la famille des USP et CDKN1A pourraient représenter de nouvelles cibles thérapeutiques dans les LMA. / There is a high rate of drug resistance in acute myeloid leukemia (AML) which may be associated with TP53 alterations. The « Ubiquitin specific peptidases » (USP) are involved in several cancers but their roles in AML are not elucidated. Gene expression analysis of 21 USP and genes of the USP7-MDM2-TP53-CDKN1A axis by quantitative RT-PCR in 111 AML samples, showed a deregulation of USP44, USP1, USP28 and CDKN1A in respectively 72%, 44%, 25% and 42% of cases. CDKN1A, an important TP53 target, may have a role in treatment resistance. We have developed an experimental model to assess the response of leukemic cells to doxorubicin and nutlin 3, a non genotoxic TP53 modulator, in relation to the CDKN1A expression level. This preliminary work suggests that some members of the USP family and CDKN1A could represent novel therapeutic targets in AML.

No description available.

O câncer de colo do útero é o terceiro tipo de câncer mais frequente em mulheres no mundo, e a infecção persistente pelo papilomavirus humano (HPV) oncogênico é condição necessária, mas não suficiente para seu desenvolvimento. As oncoproteínas virais E6 e E7 interferem direta ou indiretamente na ação de várias proteínas celulares. Entretanto, as variantes proteicas, resultantes de polimorfismos genéticos, podem apresentar comportamento distinto mediante a infecção pelo HPV. O objetivo deste estudo foi avaliar possíveis associações entre polimorfismos nos genes TP53 (p53 PIN3, p53 72C>G) e p21 (p21 31C>A) e o desenvolvimento de neoplasias cervicais, considerando os níveis de expressão das proteínas p53, p21, p16 e ciclina D1, e fatores de risco clássicos para o câncer cervical. Foram selecionadas 466 mulheres residentes no Rio de Janeiro, 281 com diagnóstico histopatológico de neoplasia cervical de baixo (LSIL) e alto grau (HSIL) e câncer (grupo de casos) e 185 sem história atual ou pregressa de alteração citológica do colo uterino (grupo controle). A técnica de PCR-RFLP (reação em cadeia da polimerase - polimorfismo de comprimento de fragmento de restrição), foi empregada na análise dos polimorfismos p53 72C>G e p21 31C>A, usando as enzimas de restrição BstUI e BsmaI, respectivamente. A avaliação do polimorfismo p53 PIN3 (duplicação de 16 pb) foi feita por meio da análise eletroforética direta dos produtos de PCR. A expressão das proteínas p53, p21, p16, ciclina D1 e Ki-67 e a pesquisa de anticorpos anti-HPV 16 e HPV pool foram avaliadas por imunohistoquímica (Tissue Microarray - TMA) em 196 biópsias do grupo de casos. O grupo controle se mostrou em equilíbrio de Hardy-Weinberg em relação aos três polimorfismos avaliados. As distribuições genotípicas e alélicas relativas a p53 PIN3 e p53 72C>G nos grupos controles e de casos não apresentaram diferenças significativas, embora o genótipo p53 72CC tenha aumentado o risco atribuído ao uso de contraceptivos das pacientes apresentarem lesões mais severas (OR=4,33; IC 95%=1,19-15,83). O genótipo p21 31CA(Ser/Arg) conferiu proteção ao desenvolvimento de HSIL ou câncer (OR=0,61, IC 95%=0,39-0,97), e modificou o efeito de fatores de risco associados à severidade das lesões. A interação multiplicativa de alelos mostrou que a combinação p53 PIN3A1, p53 72C(Pro) e p21 31C(Ser), representou risco (OR=1,67, IC95%=1,03-2,72) e a combinação p53 PIN3A1, p53 72C(Pro) e p21 31A(Arg) conferiu efeito protetor (OR=0,26, IC95%=0,08-0,78) para o desenvolvimento de HSIL e câncer cervical. Observou-se correlação positiva da expressão de p16 e p21 e negativa da ciclina D1 com o grau da lesão. A distribuição epitelial de p16, Ki-67, p21 e p53 se mostrou associada à severidade da lesão. Os polimorfismos analisados não apresentaram associação com a expressão dos biomarcadores ou positividade para HPV. Nossos resultados sugerem a importância do polimorfismo p21 31C>A para o desenvolvimento das neoplasias cervicais e ausência de correlação dos polimorfismos p53 PIN3 e p53 72C>G com a carcinogênese cervical, embora alguns genótipos tenham se comportado como modificadores de risco. Nossos resultados de TMA corroboram o potencial de uso de biomarcadores do ciclo celular para diferenciar as lesões precursoras do câncer cervical. / Cervical cancer is the third most common female cancer worldwide, and persistent infection by the Human Papillomavirus (HPV) is a necessary but not sufficient condition to cause it. The viral oncoproteins E6 and E7 interfere directly or indirectly with the action of various cellular proteins. However, the protein variants, resulting from genetic polymorphisms, may act differently when encountering HPV infection. The aim of this study was to evaluate possible associations between polymorphisms in the TP53 (p53 PIN3, p53 72C>G) and p21 (p21 31C>A) genes, and the development of cervical neoplasia, considering the expression levels of p53, p21, p16 and cyclin D1 proteins, together with classic risk factors for cervical cancer. A total of 466 women resident in Rio de Janeiro were selected, being 281 with histopathological diagnosis of low (LSIL) or high grade (HSIL) cervical neoplasia or cancer (test group), and 185 with no current or previous history of alteration of cervical cytology (control group). The PCR-RFLP technique (polymerase chain reaction restriction fragment length polymorphism) was used to analyze the p53 72C>G and p21 31C>A polymorphisms, using BstUI and BsmaI restriction enzymes, respectively. Genotyping of the p53 PIN3 (duplication of 16 pb) polymorphism was performed by direct electrophoretic analysis of the PCR products. The expression of p53, p21, p16, cyclin D1 and Ki-67 proteins and the study of anti-HPV 16 and anti-HPV pool positivities were evaluated by immunohistochemisty (Tissue Microarray - TMA) in 196 biopsies of cases. The control group obeyed the Hardy-Weinberg principle in relation to the three polymorphisms analysed. The genotypic and allelic frequencies regarding p53 PIN3 and p53 72C>G in the control and test groups were not significantly different, although the p53 72CC genotype has increased the risk of more severe lesions attributed to the use of contraceptives (OR=4.33; IC 95%=1.19-15.83). The p21 31CA(Ser/Arg) genotype showed to protect against the development of HSIL or cancer (OR=0,61, IC 95%=0,39-0,97), and modified the effect of risk factors associated to the lesion severity. The multiplicative interaction of alleles showed that the combination p53 PIN3A1, p53 72C(Pro) and p21 31C(Ser) represented risk (OR=1,67, IC95%=1,03-2,72) and the combination p53 PIN3A1, p53 72C(Pro) and p21 31A(Arg) conferred protection (OR=0,26, IC95%=0,08-0,78) against the development of HSIL and cervical cancer. It was observed positive and negative correlations of, respectively, p16 and p21, and cyclin D1 expression with the cervical lesion grade. The epithelial distribution of p16, Ki-67, p21 and p53 was associated with the lesion severity. The polymorphisms analyzed showed neither association with the expression of the biomarkers nor positivity for HPV. Our results suggest the importance of polymorphism p21 31C>A in the development of cervical neoplasia and the lack of correlation between the polymorphisms p53 PIN3 and p53 72C>G with cervical carcinogenesis, although some genotypes acted as risk modifiers. Our TMA results corroborated the potential use of cell cycle biomarkers as an adjunctive tool to differentiate cervical precursor lesions.

O câncer de colo do útero é o terceiro tipo de câncer mais frequente em mulheres no mundo, e a infecção persistente pelo papilomavirus humano (HPV) oncogênico é condição necessária, mas não suficiente para seu desenvolvimento. As oncoproteínas virais E6 e E7 interferem direta ou indiretamente na ação de várias proteínas celulares. Entretanto, as variantes proteicas, resultantes de polimorfismos genéticos, podem apresentar comportamento distinto mediante a infecção pelo HPV. O objetivo deste estudo foi avaliar possíveis associações entre polimorfismos nos genes TP53 (p53 PIN3, p53 72C>G) e p21 (p21 31C>A) e o desenvolvimento de neoplasias cervicais, considerando os níveis de expressão das proteínas p53, p21, p16 e ciclina D1, e fatores de risco clássicos para o câncer cervical. Foram selecionadas 466 mulheres residentes no Rio de Janeiro, 281 com diagnóstico histopatológico de neoplasia cervical de baixo (LSIL) e alto grau (HSIL) e câncer (grupo de casos) e 185 sem história atual ou pregressa de alteração citológica do colo uterino (grupo controle). A técnica de PCR-RFLP (reação em cadeia da polimerase - polimorfismo de comprimento de fragmento de restrição), foi empregada na análise dos polimorfismos p53 72C>G e p21 31C>A, usando as enzimas de restrição BstUI e BsmaI, respectivamente. A avaliação do polimorfismo p53 PIN3 (duplicação de 16 pb) foi feita por meio da análise eletroforética direta dos produtos de PCR. A expressão das proteínas p53, p21, p16, ciclina D1 e Ki-67 e a pesquisa de anticorpos anti-HPV 16 e HPV pool foram avaliadas por imunohistoquímica (Tissue Microarray - TMA) em 196 biópsias do grupo de casos. O grupo controle se mostrou em equilíbrio de Hardy-Weinberg em relação aos três polimorfismos avaliados. As distribuições genotípicas e alélicas relativas a p53 PIN3 e p53 72C>G nos grupos controles e de casos não apresentaram diferenças significativas, embora o genótipo p53 72CC tenha aumentado o risco atribuído ao uso de contraceptivos das pacientes apresentarem lesões mais severas (OR=4,33; IC 95%=1,19-15,83). O genótipo p21 31CA(Ser/Arg) conferiu proteção ao desenvolvimento de HSIL ou câncer (OR=0,61, IC 95%=0,39-0,97), e modificou o efeito de fatores de risco associados à severidade das lesões. A interação multiplicativa de alelos mostrou que a combinação p53 PIN3A1, p53 72C(Pro) e p21 31C(Ser), representou risco (OR=1,67, IC95%=1,03-2,72) e a combinação p53 PIN3A1, p53 72C(Pro) e p21 31A(Arg) conferiu efeito protetor (OR=0,26, IC95%=0,08-0,78) para o desenvolvimento de HSIL e câncer cervical. Observou-se correlação positiva da expressão de p16 e p21 e negativa da ciclina D1 com o grau da lesão. A distribuição epitelial de p16, Ki-67, p21 e p53 se mostrou associada à severidade da lesão. Os polimorfismos analisados não apresentaram associação com a expressão dos biomarcadores ou positividade para HPV. Nossos resultados sugerem a importância do polimorfismo p21 31C>A para o desenvolvimento das neoplasias cervicais e ausência de correlação dos polimorfismos p53 PIN3 e p53 72C>G com a carcinogênese cervical, embora alguns genótipos tenham se comportado como modificadores de risco. Nossos resultados de TMA corroboram o potencial de uso de biomarcadores do ciclo celular para diferenciar as lesões precursoras do câncer cervical. / Cervical cancer is the third most common female cancer worldwide, and persistent infection by the Human Papillomavirus (HPV) is a necessary but not sufficient condition to cause it. The viral oncoproteins E6 and E7 interfere directly or indirectly with the action of various cellular proteins. However, the protein variants, resulting from genetic polymorphisms, may act differently when encountering HPV infection. The aim of this study was to evaluate possible associations between polymorphisms in the TP53 (p53 PIN3, p53 72C>G) and p21 (p21 31C>A) genes, and the development of cervical neoplasia, considering the expression levels of p53, p21, p16 and cyclin D1 proteins, together with classic risk factors for cervical cancer. A total of 466 women resident in Rio de Janeiro were selected, being 281 with histopathological diagnosis of low (LSIL) or high grade (HSIL) cervical neoplasia or cancer (test group), and 185 with no current or previous history of alteration of cervical cytology (control group). The PCR-RFLP technique (polymerase chain reaction restriction fragment length polymorphism) was used to analyze the p53 72C>G and p21 31C>A polymorphisms, using BstUI and BsmaI restriction enzymes, respectively. Genotyping of the p53 PIN3 (duplication of 16 pb) polymorphism was performed by direct electrophoretic analysis of the PCR products. The expression of p53, p21, p16, cyclin D1 and Ki-67 proteins and the study of anti-HPV 16 and anti-HPV pool positivities were evaluated by immunohistochemisty (Tissue Microarray - TMA) in 196 biopsies of cases. The control group obeyed the Hardy-Weinberg principle in relation to the three polymorphisms analysed. The genotypic and allelic frequencies regarding p53 PIN3 and p53 72C>G in the control and test groups were not significantly different, although the p53 72CC genotype has increased the risk of more severe lesions attributed to the use of contraceptives (OR=4.33; IC 95%=1.19-15.83). The p21 31CA(Ser/Arg) genotype showed to protect against the development of HSIL or cancer (OR=0,61, IC 95%=0,39-0,97), and modified the effect of risk factors associated to the lesion severity. The multiplicative interaction of alleles showed that the combination p53 PIN3A1, p53 72C(Pro) and p21 31C(Ser) represented risk (OR=1,67, IC95%=1,03-2,72) and the combination p53 PIN3A1, p53 72C(Pro) and p21 31A(Arg) conferred protection (OR=0,26, IC95%=0,08-0,78) against the development of HSIL and cervical cancer. It was observed positive and negative correlations of, respectively, p16 and p21, and cyclin D1 expression with the cervical lesion grade. The epithelial distribution of p16, Ki-67, p21 and p53 was associated with the lesion severity. The polymorphisms analyzed showed neither association with the expression of the biomarkers nor positivity for HPV. Our results suggest the importance of polymorphism p21 31C>A in the development of cervical neoplasia and the lack of correlation between the polymorphisms p53 PIN3 and p53 72C>G with cervical carcinogenesis, although some genotypes acted as risk modifiers. Our TMA results corroborated the potential use of cell cycle biomarkers as an adjunctive tool to differentiate cervical precursor lesions.

Les extrémités des chromosomes contiennent des répétitions de séquences d’ADN appelées télomères qui empêchent l’activation inopportune de la réponse aux dommages de l'ADN afin de préserver l'intégrité génomique. Les télomères raccourcissent à chaque cycle de réplication d’ADN et la télomérase a pour fonction de contrebalancer cette érosion en allongeant les télomères. Les cellules somatiques n’expriment pas la télomérase, donc leur durée de vie est normalement limitée par ce raccourcissement progressif des télomères qui conduit à l'activation de la voie p53 entraînant un arrêt de la croissance cellulaire. En revanche, les cellules cancéreuses acquièrent l'immortalité cellulaire principalement en réactivant la télomérase ou en utilisant des méthodes alternatives d'allongement des télomères basées sur la recombinaison d’ADN. Auparavant, dans notre laboratoire, un criblage CRISPR à l'échelle du génome a été réalisé dans la lignée cellulaire pré-B NALM-6 traitée avec la molécule BIBR1532, un inhibiteur de la télomérase. Ces résultats suggéraient que cinq sous-unités du complexe de remodelage de la chromatine INO80, lorsque supprimées indépendamment, réduisaient la prolifération des cellules ayant un raccourcissement des télomères induit par le BIBR1532. Mon objectif était d'étudier cette interaction génétique afin de comprendre les processus biologiques impliqués dans cette létalité synthétique. Après l'élimination des gènes codant à la fois pour la sous-unité enzymatique de la télomérase humaine (hTERT) ainsi que les sous-unités spécifiques du complexe INO80 humain, nous avons constaté que les cellules double-négatives avaient une capacité proliférative réduite, ce qui démontre que l’interaction génétique mesurée par criblage CRISPR est bel et bien spécifique. Étant donné le rôle du facteur de transcription p53 dans la réponse cellulaire au raccourcissement télomérique, nous avons exploré l’importance de cette voie de signalisation pour l’interaction entre le complexe INO80 humain et la télomérase. Après l’activation de p53 avec un traitement avec la molécule nutlin-3a, les niveaux d'expression de plusieurs cibles de p53 tels que MDM2 et CDKN1A ont augmenté dans les cellules ayant une délétion du gène NFRKB, codant pour une sous-unité du complexe INO80 humain. Les cellules ayant une délétion du gène UCHL5, codant pour le partenaire d’interaction de NFRKB, ont également montré une augmentation de l’expression de MDM2 lorsque traitées avec nutlin-3a. Enfin, la perte de télomérase (hTERT) modifie les niveaux d'expression des composants de la 2 voie p53 CDKN1A, BAX et MDM2. En conclusion, la suppression des gènes codant pour des sous-unités du complexe INO80 telles que NFRKB ou UCHL5 est nuisible aux cellules ayant une délétion de la télomérase. Le complexe INO80 humain peut être impliqué dans l'inhibition de la voie p53, en réponse à l'activation de p53 soit par des télomères courts ou avec un traitement avec nutlin-3a. Des recherches plus approfondies sur cette interaction génétique pourraient mener au développement de nouvelles thérapies combinatoires afin d’inhiber la croissance des cellules cancéreuses. / The ends of chromosomes contain telomeric repeats that prevent the DNA damage response from being activated in order to preserve genomic integrity. Telomerase functions to alleviate incomplete DNA replication at telomeres, and to repair those telomeres damaged by various means including oxidative damage. The lifespan of telomerase negative somatic cells is normally restricted by gradual telomere shortening which can lead to the activation of the p53 pathway resulting in cellular growth arrest. Cancer cells often elongate their telomeres in order to acquire cellular immortality predominantly by reactivating telomerase or by using recombination-based, alternative telomere lengthening methods. Previously in our lab, a genome-wide CRISPR screen was conducted in the pre-B cell line NALM-6 treated with a small molecule inhibitor of telomerase, BIBR1532. These previous results suggested that five subunits of the INO80 chromatin-remodeling complex, when independently deleted, reduced cellular proliferation in cells with BIBR1532 induced telomere shortening. My goal was to investigate this genetic interaction in order to understand the biological processes implicated in this synthetic lethal relationship. After the knockout of the genes encoding both the enzymatic subunit of human telomerase (hTERT) and specific subunits of the human INO80 complex, I found that the proliferative capacity of NALM-6 cells was reduced. This result indicates the genetic interaction identified by CRISPR screening is in fact specific. In addition, after p53 stimulation with nutlin-3a treatment, expression levels of the p53 pathway component MDM2 were altered after the knockout of the genes encoding specific subunits of the human INO80 complex, NFRKB and UCHL5, individually. CDKN1A expression was also altered after nutlin-3a treatment and NFRKB knockout. Finally, the loss of telomerase (hTERT) alters the expression levels of the p53 pathway components CDKN1A, BAX and MDM2. In conclusion, the deletion of the genes encoding specific subunits of the INO80 complex, including NFRKB and UCHL5, is harmful to cells after hTERT knockout. The human INO80 complex may be involved in inhibiting the p53 pathway, in response to p53 activation by short telomeres or nutlin-3a treatment. Further investigation into this synthetic lethal relationship may shed light on new combinatorial therapeutics in cancer.