Chronic Hepatitis B Virus (HBV) infection is a global health problem because of its connection to acute and chronic liver diseases as well as hepatocellular carcinoma (HCC). There is increasing evidence showing that HBV contributes to HCC due to persistently high levels of trans-activating protein---hepatitis B encoded x antigen (HBxAg). Studies have shown that the HBxAg affects and alters the activity of many different transcription factors and plays an essential role in several cytoplasmic signaling transduction pathways, such as Wnt signaling pathways. One of the upregulated genes, designated URG11, was found transactivated by HBxAg. URG11 could stimulate the ß-catenin promoter and hepatocellular growth and survival which suggest that URG11 may be a regulatory element in the ß-catenin signaling pathways. microRNA148a (miR148a) was identified from two miRNA microarrays as one of the up-regulated miRNAs in cells stably expressing HBxAg or over-expressing URG11. Moreover, the expression of miR148a was also elevated in HBV-mediated HCC patient tissue samples. To study the function of miR148a, HepG2 (hepatoblastoma) and Hep3B (hepatoma) cells stably expressing HBxAg or over-expressing URG11 were transduced by recombinant lentiviruses encoding anti-miR148a. anti-miR148a suppressed cell proliferation, cell cycle progression, cell migration, anchorage independent growth in soft agar and subcutaneous tumor formation in SCID mice. Further, introduction of anti-miR148a increased PTEN protein and mRNA expression, suggesting that PTEN was suppressed by miR148a. In addition, anti-miR148a blocked the stimulation of Akt signaling, resulting in decreased expression of ß-catenin. Thus, miR148a may play a central role in HBxAg/URG11 mediated HCC, and may be an early diagnostic marker and/or therapeutic target associated with this tumor type. / Biology

Circadian rhythms are daily molecular oscillations within cells ranging from prokaryotes to humans. This rhythm is self sustaining, and receives external cues in order to synchronize an organism's behavior and physiology with the environment. Many metabolites utilized in metabolic processes seem to follow a pattern of circadian oscillation. Iron, an essential component in cellular processes such as respiration and DNA synthesis, is obtained almost exclusively through diet, yet little is known about how the clock governs iron metabolism. The regulation of iron within the cell is very tightly controlled, as iron is highly reactive in the generation of oxidative stress and the excretion of excess iron is very limited. There are limited findings indicating that there are molecular ties between the circadian clock and the regulation of iron metabolism. The first half of my dissertation focuses on the role of the circadian clock in modulating expression of iron metabolic components. We found that key components of iron import, in TFRC, and export, in SLC40A1, show altered expression in response to changes in the expression of clock transcription components. Furthermore, in circadian synchronized HepG2 hepatocytes TFRC and SLC40A1 showed rhythms in their mRNA expression, although expression of these genes was highly altered in conditions of high iron availability. We also examined IREB2, which expresses a master regulator of iron concentration in IRP2. IRP2 showed rhythms in phase with circadian component PER2, and IRP2's rhythmicity was lost under iron overload conditions. We observed that the ability of these three critical iron metabolic components to respond to sudden increases in available iron was mitigated in cells with clock impairment. Whole cistrome and transcriptome analysis was used to determine that rhythmicity in TFRC and SLC40A1 are not equal in their recruitment of circadian protein binding or in the stage of transcription in which circadian rhythms are generated. The cumulative effect of all of this regulation is that rhythmic variation in intracellular hepatic ferrous iron is clock controlled. The second half of my dissertation focuses on understanding how iron uptake influences clock resetting. Initially, iron was added to the cells in the form of ferrous sulfate, or chelated out of the cells using 2-2'-dipyridyl and clock gene expression was monitored. Altered rhythmicity of these components was seen at both the mRNA and protein level in cells with disrupted iron homeostasis. Then, we measured changes in period, phase, and amplitude of these rhythms, ultimately using a luciferase reporter cell line to demonstrate that even slight changes in cellular iron produce an effect on rhythmic period. We find that the circadian clock and iron metabolism pathway are intimately related, and that the intracellular iron concentration plays a role in circadian clock behavior. Overall, our research illustrates the importance of the circadian clock in liver metabolism and physiology. Improper iron metabolism due to genetic or dietary shortcomings is common in humans, and our work builds on the importance of chronotherapy in treatment of these conditions. Conversely, our research into the effect intracellular iron has on the clock contributes to the growing body of research into how circadian clocks, especially the peripheral clock of the liver, receive input from a range of metabolites in conjunction with signals from the master oscillator of the suprachiasmatic nucleus. / Ph. D.

Les adénomes hépatocellulaires (AHC) sont des tumeurs hépatiques bénignes rares se développant chez la femme jeune suite à la prise de contraceptifs oraux et pouvant se compliquer d’hémorragie et de transformation maligne en carcinome hépatocellulaire (CHC). Une classification génotype/phénotype a mise en évidence trois groupes d’AHC : les AHC inactivés pour le facteur de transcription HNF1A, les AHC mutés pour la β-caténine et les AHC dit « inflammatoires » ayant une activation de la voie JAK/STAT. Nous avons identifiés des mutations activatrices du gènes GNAS, codant pour la sous unité alpha de la protéine Gs, dans un sous-groupe d’AHC inflammatoires ainsi que chez des patients avec des AHC et atteints d’un syndrome de McCune Albright, une maladie rare combinant des tumeurs endocriniennes, une dysplasie fibreuse osseuse et des taches cutanés café au lait. Cette découverte confirme les interactions entre la voie de l’AMP cyclique induite par les mutations GNAS et la voie JAK/STAT. Les CHC sont les tumeurs primitives du foie les plus fréquentes, survenant souvent sur un foie cirrhotique exposé à différents facteurs de risque comme l’hépatite B chronique, l’hépatite C chronique, l’alcool ou le syndrome métabolique. Le CHC est le résultat de l’accumulation d’altérations génétiques et épigénétiques. Premièrement, nous avons identifiés les mutations du promoteur de TERT (Telomerase reverse transcriptase) comme les altérations génétiques somatiques les plus fréquentes des CHC. Ces mutations ont été aussi retrouvées dans des lésions prénéoplasiques développées sur cirrhose suggérant leurs rôles précoces dans l’initiation tumorale et la transformation maligne. A l’inverse l’étude des mutations du promoteur de TERT et la réalisation de séquençage haut-débit dans les AHC et les transformation d’adénome en CHC nous a permis de disséquer les mécanismes de transformation maligne sur foie sain avec la présence de manière précoce d’une mutation de la β-caténine et dans un second temps l’apparition d’une mutation dans le promoteur de TERT. Par la suite, nous avons mis en évidence une signature moléculaire pronostique transcriptomique chez les patients avec CHC traités par résection hépatique. Cette signature moléculaire prédisant à la fois la récidive tumorale et le décès a été validée dans des cohortes de patients à l’étranger. Enfin, nous avons mise en évidence le rôle oncogénique de l’adeno-associated virus de type 2 dans la survenue de CHC sur foie sain via un mécanisme de mutagénèse insertionnelle dans des gènes clés de la carcinogénèse comme TERT, CCNA2, MLL4 ou TNFSF10. Ces résultats ont permit de mettre en évidence de nouveaux facteurs de risque viraux de survenue du CHC, d’identifier de nouvelles altérations génétiques impliquées dans la transformation maligne sur cirrhose et sur foie sain et permit de développer une signature moléculaire pronostique qui pourrait être utiliser dans le futur comme une aide à la stratification thérapeutique chez les patients atteint de CHC. / Hepatocellular adenomas (HCA) are rare benign liver tumors occuring in young women taking oral contraception and complications as haemorrhage or malignant transformation in hepatocellular carcinomes (HCC) could occur. A genotype/phenotype classification has defined different subgroups of tumors : HCA with inactivating mutations of HNF1A, HCA with activating mutations of β-catenin and inflammatory HCA with activation of the JAK/STAT pathway. We have identified activation mutations of GNAS, that codes for the alpha subunit of the Gs protein in a subgroup of inflammatory HCA and in patients with HCA and McCune Albright syndrom, a rare disease that combined endocrine tumor, bone fibrous dysplasia and « cafe au lait » skin macula. These findings highlight the crosstalk between the cyclic AMP pathway induced by GNAS mutation with the JAK/STAT pathway. HCC are the most frequent primary liver tumors worldwide and mainly occur on cirrhosis due to various risk factor as hepatitis B and C virus, alcohol consumption and metabolic syndrome. HCC is due to the accumulation of genetic and epigenetic alterations in the malignant hepatocytes. We have identified TERT (telomerase reverse transcriptase) promoter mutations as the most frequent somatic genetic alterations in HCC. These mutations were also found in cirrhotic premalignant nodules underlying their role in tumor initiation and malignant transformation. In contrast, the study of the different steps of malignant transformation of HCA into HCC using next generation sequencing and TERT promoter screening have shown that activatiing mutation of β-catenin is an early genetic alteration whereas TERT promoter mutation is required in a second step to promote a full malignant transformation. We have also identified a prognostic molecular signature, the 5-gene score, in patients with HCC treated by liver resection. The 5-gene score predicts tumor recurrence and disease specific survival and has been validated in different cohorts of patients worldwide. Finally, we have shown that adeno-associated virus type 2 is involved in liver carcinogenesis on normal liver through insertional mutagenesis in key cancer genes as TERT, CCNA2, MLL4 and TNFSF10. These results have underlined a new oncogenic virus involved in HCC development, identified new genetic alterations involved in malignant transformation on cirrhosis and normal liver and a new prognostic molecular signature that will help to guide treatment of patients with HCC in the future.

Yau Mei-sze. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references (leaves 96-112). / Abstracts in English and Chinese. / Abstract / Abstract (Chinese Version) / Acknowledgements / List of Abbreviations / Table of Contents / List of Tables / List of Figures / Chapter Chapter 1 --- Introduction / Chapter Chapter 2 --- Literature Review / Chapter 2.1 --- Hepatocellular Carcinoma / Chapter 2.2 --- Epidermal Growth Factor Receptor / Chapter 2.2.1 --- Activation of Epidermal Growth Factor Receptor / Chapter 2.2.2 --- Epidermal Growth Factor Receptor Signaling Pathways / Chapter 2.2.3 --- Expression Level and Patient Survival / Chapter 2.2.4 --- Epidermal Growth Factor Receptor Activity and Tumor Cell Growth / Chapter 2.2.5 --- Epidermal Growth Factor Receptor Activity and Radiation / Chapter 2.3 --- "Epidermal Growth Factor Receptor Tyrosine Kinase Inhibitor, ZD1839" / Chapter 2.3.1 --- Tumor Cell Growth Control Activities of ZD1839 / Chapter 2.3.2 --- Factors Affecting the Tumor Cell Growth Control Activities of ZD1839 / Chapter 2.3.3 --- Radiosensitization Activities of ZD1839 / Chapter 2.3.4 --- Factors Affecting the Radiosensitization Activities of ZD1839 / Chapter 2.4 --- Study Objectives / Chapter Chapter 3 --- Materials and Methods / Chapter 3.1 --- ZD1839 / Chapter 3.2 --- Cell lines and Cell Culture / Chapter 3.3 --- Immunoblot Analysis / Chapter 3.3.1 --- Total Protein Extraction / Chapter 3.3.2 --- Protein Amount Determination / Chapter 3.3.3 --- Protein Separation / Chapter 3.3.4 --- Blotting / Chapter 3.3.5 --- Antibody Labeling / Chapter 3.3.6 --- Detection of Antibody Binding / Chapter 3.4 --- Cytotoxicity Assay / Chapter 3.5 --- Nucleotide sequence analysis / Chapter 3.5.1 --- Total RNA Extraction / Chapter 3.5.2 --- RNA Amount Determination / Chapter 3.5.3 --- Reverse Transcription - Polymerase Chain Reaction (RT-PCR) / Chapter 3.5.3.1 --- Reverse Transcription / Chapter 3.5.3.2 --- High Fidelity Polymerase Chain Reaction / Chapter 3.5.4 --- Purification of PCR Product / Chapter 3.5.5 --- Cycle Sequencing Reaction / Chapter 3.5.6 --- DNA Precipitation and Sequencing / Chapter 3.6 --- Clonogenic Assay / Chapter 3.7 --- Immunohistochemical Analysis / Chapter Chapter 4 --- Results / Chapter 4.1 --- Immunoblot Analysis / Chapter 4.2 --- Cytotoxicity Assay / Chapter 4.2.1 --- Effect of ZD 1839 on cell morphology / Chapter 4.2.2 --- Effect of ZD 1839 on cell growth / Chapter 4.3 --- Nucleotide sequence analysis / Chapter 4.3.1 --- RNA Concentration of HCC cells / Chapter 4.3.2 --- Sequencing of TK domain within EGFR / Chapter 4.3.3 --- Sequencing of TK domain within HER2 / Chapter 4.4 --- Clonogenic assay / Chapter 4.4.1 --- Effects of ZD 1839 pre-treatment on radiation response / Chapter 4.4.2 --- Effects of ZD 1839 continuous treatment on radiation response / Chapter 4.5 --- Immunohistochemical Analysis / Chapter Chapter 5 --- Discussion / Chapter 5.1 --- Important Findings / Chapter 5.2 --- EGFR Expression of HCC Cells / Chapter 5.3 --- Cytotoxicity of ZD1839 on HCC Cell Lines / Chapter 5.4 --- Factors Affecting the Cytotoxicity of ZD1839 / Chapter 5.4.1 --- Effect of EGFR Expression on ZD1839 Cytotoxicity / Chapter 5.4.2 --- Effect of EGFR Mutations on ZD 1839 Cytotoxicity / Chapter 5.4.3 --- Effect of HER2 Expression on ZD1839 Cytotoxicity / Chapter 5.4.4 --- Effect of HER2 Mutations on ZD 1839 Cytotoxicity / Chapter 5.5 --- Radiation Response ofHCC Cell Lines upon ZD1839 Treatment / Chapter 5.6 --- Factors Affecting Radiation Response of ZD1839-treated HCC Cell Lines / Chapter 5.6.1 --- Effect of Growth Arrest on Radiation Response of HCC Cell Lines / Chapter 5.6.2 --- Other Factors Affecting Radiation Response of HCC Cell Lines / Chapter Chapter 6 --- Conclusion / References

Made available in DSpace on 2016-01-26T12:51:38Z (GMT). No. of bitstreams: 1 raphaelraphe_dissert.pdf: 1654822 bytes, checksum: 678de193b930e82d2dafeef1d384be12 (MD5) Previous issue date: 2012-09-24 / Introduction: Hepatocellular carcinoma (HCC) is the most common primary neoplasm of the liver. It constitutes an important cause of cancer mortality in cirrhotic patients. Objective: To evaluate the epidemiological aspects relating them to the risk factors of HCC in a closed population. Methods: We conducted a retrospective cross-sectional study with chart review of patients treated from November 1998 to May 2011 in the Departments of Liver Transplantation, Gastroenterology and Pathology and the Cancer Institute of the Hospital de Base, São José do Rio Preto. The study was approved by the Ethics and Research. Results: A total of 272 patients with HCC, 229(84.2%) were male and 43 (15.8%) were female. The mean age was 57.1 years (SD 10.9 years) and predominantly caucasian (91.5%). Cirrhosis present in 98.2% with Child-Turcotte-Pugh class B in 104 patients (38.9%). The etiology, the most frequent was infection with hepatitis C virus in 145(55.1%) patients being single cause in 88(33.4%). The results suggest that sex is associated with the principal factors in the etiology of HCC, but age was not associated with disease etiology. In 220 patients, the largest nodule, ranged from 6mm to 260mm in diameter with a mean of 61.4mm (SD 41.5mm). In 145(64.2%) patients revealed the presence of a nodule and 46(20.3%) patients multifocal. It was found that 8(3.6%) only nodules had a diameter smaller than 20mm and 74(33.5%) diameters of between twenty and fifty millimeters. Of the 214 patients classified according to staging, 70(32.7%) were early stage and 97 among more advanced stage and terminal (30.4% and 14.9% respectively). Thirty(11%) patients were incidental findings. Regarding the diagnosis of HCC, 175 patients (68.1%) were diagnosed by an imaging study. The time between diagnosis and initial treatment, a total of 224 patients, 86(38.4%) was started in the first month and 46(20.5%) between 30 and 60 days. The average start of treatment was 70.7 days (SD 86.1 days), specific treatment was conducted in 236(86.8%) patients in which chemoembolization 127(46.7%) and liver transplantation in 72(26.5%), of whom 33(45.8%) received chemoembolization as a "bridge" to transplant. Thirty-four patients (12.5%) received only supportive therapy. Level of α-fetoprotein was measured in 209 patients with 29.2% less than 20 ng/ml and 34.9% at above 400 ng/ml. In patients with thyroid nodules diameter greater than or equal to 10 cm, were 67.8% α-fetoprotein levels greater than 400 ng / ml. In 144 patients, histological analysis showed that in 94 (65.3%) nodules were moderately differentiated. Conclusion: Prevalence of male and involvement in the 5th decade of life. Hepatic cirrhosis present in most patients. Infection with hepatitis C followed by alcoholic liver disease were more common etiologies. Diagnosis was delayed or advanced stages, and dosage levels of α-fetoprotein was not good tool diagnostic. Treatment of HCC showed a predominance of non-curative therapies due to late diagnosis. / Introdução: Carcinoma hepatocelular (CHC) é a neoplasia primária mais comum do fígado. Constitui-se em importante causa de mortalidade por câncer em pacientes cirróticos. Objetivo: Avaliar os aspectos epidemiológicos relacionando-os com os fatores de risco do CHC em uma população fechada. Casuística e Métodos: Foi realizado um estudo transversal retrospectivo, com revisão de prontuários de pacientes atendidos de novembro de 1998 a maio de 2011 nos Serviços de Transplante de Fígado, Gastroenterologia, Anatomia Patológica e do Instituto do Câncer do Hospital de Base de São José do Rio Preto. O estudo foi aprovado pelo Comitê de Ética e Pesquisa. Resultados: Do total de 272 pacientes com CHC, 229(84,2%) eram do sexo masculino e 43(15,8%) do sexo feminino. A idade média foi de 57,1 anos (desvio padrão de 10,9 anos) e predomínio da raça branca (91,5%). Cirrose hepática presente em 98,2% com classificação de Child-Turcotte-Pugh classe B em 104 pacientes (38,9%). Quanto à etiologia, a mais frequente foi infecção por vírus da hepatite C em 145(55,1%) pacientes, sendo causa isolada em 88(33,4%) pacientes. Os resultados sugerem que o sexo esteja associado aos principais fatores da etiologia do CHC, mas a idade não apresentou associação com a etiologia da doença. Em 220 pacientes, o maior nódulo, variou de 6mm a 260mm de diâmetro com média de 61,4mm (desvio padrão de 41,5mm). Em 145 pacientes (64,2%), observou-se presença de um nódulo, dois nódulos em 26(11,5%), três nódulos em 9(4%) e 46 pacientes (20,3%) multifocal. Verificou-se que 8(3,6%) nódulos únicos apresentavam diâmetro menor que 20mm e 74(33,5%) diametros entre dois e cinco cm. Dos 214 pacientes classificados quanto ao estadiamento de acordo com o Barcelona Clinic Liver Cancer (BCLC), 70(32,7%) eram estadio precoce e 97 entre estadios avancado e terminal (30,4% e 14,9% respectivamente). Trinta pacientes (11%) foram achados incidentais. Quanto ao diagnostico de CHC, 175 pacientes (68,1%) foram diagnosticados por meio de um exame de imagem. Quanto ao tempo entre o diagnostico e o primeiro tratamento, de um total de 224 pacientes, 86 (38,4%) foi iniciado no primeiro mes e 46(20,5%) entre 30 e 60 dias. A media para o inicio do tratamento foi de 70,7 dias (desvio padrao de 86,1 dias), Tratamento especifico foi realizado em 236(86,8%) pacientes sendo quimioembolizacao exclusiva em 127(46,7%) e transplante de figado em 72 (26,5%) e destes, 33(45,8%) receberam quimioembolizacao como gponte h para o transplante. Trinta e quatro pacientes (12,5%) receberam apenas terapia de suporte. Nivel de ¿-fetoproteina foi dosado em 209 pacientes, com 29,2% menor que 20 ng/ml e 34,9% niveis superiores a 400 ng/ml. Em pacientes com nodulos de diametro maior ou igual a 100 mm, 67,8% apresentaram ¿-fetoproteina com niveis superiores a 400 ng/ml. Em 144 pacientes, a analise histologica apontou que em 94(65,3%) os nodulos eram moderadamente diferenciados. Conclusao: Predominio do sexo masculino e acometimento na 5a decada de vida. A cirrose hepatica foi o principal fator de risco para CHC. Infeccao do virus da hepatite C seguida de doenca hepatica alcoolica foram etiologias mais frequentes. Diagnostico ocorreu nas fases tardia ou avancada na maioria dos pacientes e a dosagem dos niveis de ¿-fetoproteina nao se mostrou boa ferramenta diagnóstica. Tratamento do CHC apresentou predomínio de terapias não curativas devido ao diagnóstico tardio.

Les adénomes hépatocellulaires (AHC) sont des tumeurs bénignes rares qui se développent le plus souvent chez la femme jeune suite à la prise de contraceptifs oraux. Les complications principales sont l’hémorragie et plus rarement, la transformation maligne en carcinome hépatocellulaire (CHC). Des travaux récents ont permis d’identifier 3 groupes moléculaires principales d’AHC qui se définissent par (1) l’inactivation du facteur de transcription HNF1A (H-HCA), (2) l'activation de la voie Wnt/ß-caténine (bHCA) ou (3) la présence d’infiltrats inflammatoires (IHCA).Afin d’identifier les voies de tumorigenèse associées au développement d’AHC inflammatoires (IHCA), une analyse transcriptomique comparant des IHCA à des foies non tumoraux a été réalisée au laboratoire, ce qui a permis d’identifier dans ce groupe tumoral une activation de la voie IL-6/JAK/STAT3. Nous avons recherché de nouvelles altérations géniques et nous avons caractérisé le mécanisme d'activation de la voie IL-6/JAK/STAT dans les IHCA. Les conséquences fonctionnelles sur la voie STAT3 des différents mutants ont été analysées par une modélisation de leur expression dans des lignées hépatocellulaires. Par ailleurs, nous avons réalisé des études génomiques intégrées (analyse CGH-SNP, méthylome et séquençage exome) sur une large série de 250 AHC avec pour objectif d’affiner la classification moléculaire des AHC, d’identifier de nouveaux gènes altérés dans ces tumeurs et d’élucider les mécanismes de transformation maligne des AHC en CHC.Dans le groupe des IHCA, ces analyses nous ont permis d’identifier de nombreux oncogènes activés par mutation somatique ; de plus, trois de ces gènes n’avaient jamais été décrits comme étant mutés dans des tumeurs humaines. Nous avons identifié des mutations activatrices du récepteur à l’IL-6, gp130 dans 60% des IHCA. Nous avons aussi retrouvé des mutations de FRK, une src-like kinase, dans 10% des IHCA, du facteur de transcription STAT3 dans 5% des IHCA, du gène GNAS dans 5% des cas, et de la tyrosine kinase JAK1 dans 1% des cas. Toutes les mutations identifiées étaient somatiques, monoalléliques et mutuellement exclusives. Nous avons pu montrer, dans des systèmes de lignées cellulaires hépatocellulaires, que l'expression des formes mutées de ces gènes est capable d’activer la voie IL-6/STAT3 en absence du ligand IL-6, contrairement aux protéines sauvages. Nous avons identifié des inhibiteurs pharmacologiques qui permettent d’inhiber de façon spécifique ces mutants et qui pourraient être utilisés en clinique pour le traitement des IHCA.Grâce à une technique de CGH-SNP, nous avons identifié des événements récurrents de pertes et gains de chromosomes associés aux groupes moléculaires d’AHC. De façon similaire, l’étude de la méthylation dans les AHC a permis de mettre en évidence un pattern spécifique à chaque sous groupe. Nous avons montré que l’instabilité chromosomique augmente progressivement dans les lésions borderline et dans les CHC développés sur AHC comparés aux AHC classiques. Le séquençage exome de 5 transformations malignes de AHC en CHC a identifié un nombre plus important de mutations dans les AHC qui ont transformé comparé aux AHC classiques ; ce nombre est significativement augmenté dans la partie CHC des tumeurs. La comparaison de la partie bénigne et maligne des tumeurs a mis en évidence l'activation de ß-caténine comme un évènement précoce dans le processus de transformation et a révélé la présence de mutations somatiques fréquentes dans le promoteur de la télomèrase (TERT), identifiées principalement dans la partie maligne des tumeurs.En conclusion, cette étude a permis d’identifier des mécanismes distincts conduisant à l'activation de STAT3 dans les IHCA, renforçant le rôle de la voie JAK-STAT3 dans la tumorigenèse bénigne hépatocellulaire ainsi que le lien entre Src kinases et inflammation. Ces travaux ont permis d’affiner la classification moléculaire des AHC avec des corrélations étroites... / Hepatocellular adenomas (HCA) are rare benign tumors that develop most often in young women after taking oral contraception. The main complications are hemorrhage and rarely, malignant transformation to hepatocellular carcinoma (HCC). Recent work in the laboratory identified three main HCA molecular groups that are defined by (1) inactivation of the transcription factor HNF1A (H-HCA), (2) activation of the Wnt/ß-catenin pathway (bHCA) or (3) the presence of inflammatory infiltrates (IHCA).To identify tumorigenesis pathways associated with the development of inflammatory HCA (IHCA), a transcriptome analysis comparing IHCA to non-tumor liver was performed in the laboratory, leading to the identification of an activation of the IL-6/JAK/STAT3 pathway in these tumors. We sought new gene alterations and we characterized the activation mechanism of the IL-6/JAK/STAT pathway in IHCA. The functional consequences of the different mutants on the STAT3 pathway were analyzed by modeling their expression in hepatocellular cell lines. In addition, we performed integrated genomic studies (CGH-SNP analysis, methylome and exome sequencing) on a wide range of 250 HCA with the aim to refine the molecular classification of HCA, to identify new genes altered in these tumors and to elucidate the mechanisms of malignant transformation of HCA to HCC.In the group of the IHCA, we identified many oncogenes activated by somatic mutation; in addition, three of these genes were never been described as mutated in human tumors. We identified activating mutations in the IL-6 receptor gp130 in 60% of IHCA. We also found mutations in FRK, a src-like kinase, in 10% of IHCA, of the transcription factor STAT3 in 5% of IHCA, of the GNAS gene in 5% of cases, and of the tyrosine kinase JAK1 in 1% of the cases. All identified mutations were somatic and monoallelic and were mutually exclusive. We have shown in hepatocellular cell lines that the expression of mutated forms of these genes is able to activate the IL-6/STAT3 pathway in the absence of the IL-6 ligand, in contrast to wild-type proteins. We have identified pharmacological inhibitors that specifically inhibit the mutants and that could be used for the clinical treatment of IHCA.Using a CGH-SNP technique, we identified recurrent chromosomes gains and losses associated with the HCA molecular groups. Similarly, the study of methylation in HCA highlighted a specific pattern in each subgroup. We showed that chromosomal instability increases gradually in borderline lesions and in HCC developed on HCA compared to classical HCA. Exome sequencing of 5 malignant transformation of HCA to HCC identified a large number of mutations in the transformed HCA compared to classical HCA; and this number is significantly increased in HCC tumors counterpart. Comparison of benign and malignant tumors highlighted the activation of ß-catenin as an early event in the transformation process and revealed frequent somatic mutations in the promoter of the telomerase gene (TERT), identified mainly in the malignant part of tumors.In conclusion, this study has led to the identification of distinct mechanisms leading to the activation of STAT3 in IHCA, strengthening the role of the JAK-STAT3 pathway in benign hepatocellular tumorigenesis and the relationship between Src kinases and inflammation. This work helped to refine the molecular classification of HCA with tight correlations between genotype and phenotype, and led to advances in the identification of major genetic determinants involved in the process of malignant transformation.

Hepatocellular carcinoma (HCC) is a common malignancy of the liver that is one of the most frequent causes of cancer-related death in the world. Surgical resection and liver transplantation are the only curative options for HCC, and tumor invasion and metastasis render many patients ineligible for these treatments. Identification of the mechanisms that contribute to invasive and metastatic disease may enlighten therapeutic strategies for those not eligible for surgical treatments. In this dissertation, I describe two sets of experiments to elucidate mechanisms underlying HCC dissemination, involving the activities of Krüppel-like factor 6 and a particular p53 point mutation, R172H. Gene expression profiling of migratory HCC subpopulations demonstrated reduced expression of Krüppel-like factor 6 (KLF6) in invasive HCC cells. Knockdown of KLF6 in HCC cells increased cell transformation and migration. Single-copy deletion of Klf6 in a HCC mouse model results in increased tumor formation, increased metastasis to the lungs, and decreased survival, indicating that KLF6 suppresses both tumor formation and metastasis in HCC. To elucidate the mechanism of KLF6-mediated tumor and metastasis suppression, we performed gene expression profiling and ChIP-sequencing to identify direct transcriptional targets of KLF6 in HCC cells. This analysis revealed novel transcriptional targets of KLF6 in HCC including CDC42EP3 and VAV3, both of which are positive regulators of Rho family GTPases. Concordantly, KLF6 knockdown cells demonstrate increased activity of the Rho family GTPases RAC1 and CDC42, and RAC1 is required for migration induced following KLF6 knockdown. Moreover, VAV3 and CDC42EP3 are also required for enhanced cell migration in HCC cells with KLF6 knockdown. Together, this work describes a novel signaling axis through which KLF6-mediated repression of VAV3 and CDC42EP3 inhibits RAC1Gmediated HCC cell migration in culture, and potentially HCC metastasis in vivo. TP53 gene mutations are commonly found in HCC and are associated with poor prognosis. Prior studies have suggested that p53 mutants can display gain-of- function properties in other tumor types. Therefore, I sought to determine if a particular hotspot p53 mutation, p53R172H, provided enhanced, gain-of-function properties compared to p53 loss in HCC. In vitro, soft agar colony formation and cell migration is reduced upon knockdown of p53R172H, indicating that this mutation is required for transformation-associated phenotypes in these cells. However, p53R172H-expressing mice did not have enhanced tumor formation or metastasis compared to p53-null mice. These data suggest that p53R172H and p53 deletion are functionally equivalent in vivo, and that p53R172H is not a gain-of-function mutant in HCC. Inhibition of the related transcription factors p63 and p73 has been suggested as a potential mechanism by which mutant p53 exerts its gain-of-function effects. Analysis of p63 and p73 target genes demonstrated that they are similarly suppressed in p53-null and p53R172H-expressing HCC cell lines, suggesting a potential explanation for the phenotypes I observed in vivo and in vitro. Together, the studies described in this dissertation increase our understanding of the mechanisms underlying HCC progression and metastasis. Specifically, we find and characterize KLF6 as a novel suppressor of HCC metastasis, and determine the contribution of a common p53 point mutation in HCC. This work contributes to ongoing efforts to improve treatment options for HCC patients.

Background: Hepatocellular Carcinoma (HCC) is the third most common cause of cancer related death worldwide and is often diagnosed by measuring serum Alpha-fetoprotein (AFP); a stand-alone biomarker with limited diagnostic proficiency. To compensate for this, AFP is commonly used in conjunction with high performance imaging and radiological methods. However, as the burden of HCC is predominantly in the developing world where such technologies are not readily available, it is imperative that efforts are made to pursue the discovery of novel, high performance, easy to measure and robust biomarkers. With the aim of improving on the diagnostic ability of AFP, our project focuses on the study of plasma proteins as identified by Mass Spectrometry (MS) in order to investigate differences seen in the respective proteomes of controls and subjects with liver cirrhosis (LC) and HCC. Methods: Matrix Assisted Laser Desorption Ionization Time-of-Flight MS (MALDI-TOF MS) was first attempted on weak cation exchange (WCX) fractionated plasma in a pilot selection of forty subjects. On the main case-control group, quantitative MS analysis using liquid chromatography electro spray ionization quadrupole time-of-flight (LC-ESI Q-TOF) was conducted on 339 subjects using a pooled expression profiling approach. Enzyme-linked immunosorbent assays (ELISA) and 1 and 2Dimentional electrophoresis methods were performed to validate and detail candidate protein levels and modification patters in individual and pooled subjects. The human plasma used for the MS based protein discovery experiments was collected as part of a five year Liver Cancer Case-control Study (Gambia, West Africa). A smaller set of samples from subjects who formed a spectrum of non-liver disease controls, LC and HCC were obtained from the Jos University Teaching Hospital (JUTH) in Nigeria and ELISA and gel electrophoresis assays conducted on them to confirm the trends and differences seen in the Gambian subject set. Results: Bioinformatic evaluation of MALDI-TOF data highlighted peak masses 2444m/z, 2583m/z and 2559m/z to have high diagnostic abilities based on area under curve (AUC) statistics of >0.75. Of these polypeptide fragments, one was identified as the plasma glycoprotein, alpha chain fibrinogen. Results from the large-scale label free discovery experiments indicated twenty-six proteins to be differentially expressed between the three subject groups. These prospective markers include proteins previously linked to HCC as well as novel candidates, namely glutathione peroxidase 3, serum amyloid p, carboxypeptidase N and complement factors I and H which have not been implicated in the context of HCC diagnostics. Direct measurement of Hemopexin (HPX), alpha-1-antitrypsin (α1AT), apolipoprotein A1 (Apo A1) and complement component 3 (CC3) levels confirmed their change in abundance in LC and HCC versus control patients. Further biochemical characterization of glycosylated HPX isolated from glycoprotein enriched plasma sample pools showed evidence of isoelectric point shifts, indicating differential glycosylation patterns in high mannose structures of HPX which may be disease stage linked. The direct measurements of HPX, α1AT, Apo A1 & CC3 conducted on the independent Nigerian subject group also confirmed much of the trends reported from the Gambia Liver Cancer Study (GLCS) plasma. Conclusions: The independently validated, significant changes in the quantitative expression of ApoA1, α1AT, CC3 and HPX could be exploited for development into high-performance affordable assays, usable in the diagnosis and monitoring of HCC and LC patients. The unique signatures observed for most of these proteins, from liver disease free controls to LC and HCC suggest their involvement in independent pathways. As such, combining some or all of these four markers within a diagnostic panel could offer a much-needed boost in robustness and accuracy for AFP. The differences in the processing and molecular weight separation of these proteins also offers a novel inroad into biomarker identification. These suggested disease specific signatures could with further study offer highly specific biomarkers able to discern the key stages that predispose individuals to hepatocarcinogenesis. Impact: This is the first MS based discovery and extensive validation study on West African subjects whose primary cause of HCC are the Hepatitis B Virus (HBV) and fungal toxins.

Objective: The primary aim of this study was to assess patients’ preferences between radiofrequency ablation (RFA) versus hepatic resection (HR) for the treatment of small hepatocellular carcinomas (HCC). Methods: Decision analysis was performed by using probability trade-off (PTO) technique to elicit patients’ preferences and the strength of their decisions. Results: The vast majority of the study population preferred RFA over HR (70% vs. 30%, p=0.001). Their initial choice changed if 5-year survival benefit after surgery was at least 14% superior to RFA and if the 3-year disease-free survival advantage was at least 13% better than ablation. Conclusions: The results of this study suggest that fully informed cirrhotic patients would prefer RFA if diagnosed with early stage HCC even if able to undergo surgery.

Résumé : La répression fréquente du gène encodant pour le « suppressor of cytokine signaling 1 » (SOCS1) dans le carcinome hépatocellulaire (CHC) et la forte susceptibilité des souris déficientes pour SOCS1 à développer des tumeurs hépatiques expérimentales suggèrent que SOCS joue un rôle de suppresseur de tumeur. Cette notion est supportée par les études impliquant la répression de l’expression de SOCS1 via des évènements épigénétiques ou par les microARN dans plusieurs autres types de cancers. Les mécanismes moléculaires sous-jacents au rôle potentiel de suppresseur de tumeur de SOCS1 dans le foie demeurent à ce jour inconnus. Bien que les récepteurs à activité tyrosine kinase (RTK) sont reconnus pour induire l’expression de l’ARNm de SOCS1, le rôle et les mécanismes par lesquels SOCS1 peut réguler la signalisation des RTK sont incertains. Le RTK MET, qui a pour ligand le facteur de croissance des hépatocytes (HGF), régule plusieurs fonctions cellulaires normales. La dérégulation de la signalisation du récepteur MET joue des rôles importants dans la pathogenèse du CHC. Des études ont démontré que l’activation de MET promeut la prolifération, l’invasion et la migration des cellules cancéreuses du foie ainsi que leur dissémination métastatique. La signalisation aberrante de MET est un trait commun de plusieurs autres cancers et serait à l’origine de l’émergence de la résistance à la chimiothérapie. Dans ce projet, j’ai investigué les mécanismes moléculaires par lesquels SOCS1 régule l’activité du récepteur MET. Mes résultats indiquent que le foie des souris Socs1[indice supérieur -/-]Ifng[indice supérieur -/-] se régénère plus rapidement que celui des souris contrôles. Suivant une stimulation au HGF, les hépatocytes issus des souris Socs1[indice supérieur -/-] Ifng[indice supérieur -/-] présentent une augmentation de la signalisation de MET, de la migration et de la prolifération cellulaires. L’expression exogène de SOCS1 dans différentes lignées cellulaires d’hépatocarcinomes humains et murins inhibe la signalisation induite par HGF. De plus, SOCS1 diminue la prolifération, la croissance indépendante de l’anchrage et la migration dans ces lignées de CHC in cellulo et réduit de façon significative leur croissance dans les essais de xénogreffes chez les souris immunodéficientes. Mes résultats suggèrent que l’activation de la signalisation HGF-MET induit la transcription du gène SOCS1, suivi par une interaction physique entre SOCS1 et MET. L’analyse de divers mutants de SOCS1 révèle que cette interaction implique principalement les domaines SH2 et « kinase inhibitory region » (KIR) de SOCS1. L’activité kinasique de MET est requise pour cette interaction puisque l’interaction entre SOCS1 et un mutant kinase-inactif de MET est fortement réduite. SOCS1 est aussi phosphorylé en aval de MET sur quatre résidus tyrosine (Tyr). Quoique ces résidus Tyr représentent théoriquement des sites d’interaction pour des protéines adaptatrices possédant des domaines de liaison aux phospho-Tyr, elles ne semblent pas impliquées dans l’interaction de SOCS1 avec MET. Je démontre également que SOCS1 induit l’ubiquitination de MET via l’élongation de chaînes de polyubiquitine de type K48, conduisant à sa dégradation par le protéasome. Cette modulation négative de MET par SOCS1 dans les cellules CHC survient indépendamment de la voie de dégradation lysosomale de Cbl qui est partagée par plusieurs autres RTK. // Abstract : Frequent repression of the gene coding for the suppressor of cytokine signaling 1 (SOCS1) in hepatocellular carcinoma (HCC) and increased susceptibility of SOCS1 deficient mice to experimental hepatocarcinogenesis suggest a tumor suppressor role for SOCS1. This notion is supported by epigenetic and micro-RNA-mediated blockade of SOCS1 expression in several other cancers. Molecular mechanisms underlying the putative tumor suppressor function of SOCS1 in the liver have not been elucidated yet. Although receptor tyrosine kinases (RTK) can induce SOCS1 mRNA expression, the role and mechanisms of SOCS1 in regulating RTK signaling are not yet clear. c-Met is the RTK for hepatocyte growth factor (HGF) and mediates several normal cellular functions. HGF signaling and MET activation also play important roles in the pathogenesis of HCC. Experimental studies have shown that the activated MET promotes proliferation, invasion and migration of liver cancer cells and enhances metastasis. Aberrant MET signaling is a hallmark of many other cancers and underlies the emergence of chemoresistant clones. In this project, I investigated the molecular mechanisms by which SOCS1 regulates MET RTK activity. My results illustrate that the Socs1[superscript -/-]Ifng[superscript -/-] liver regenerates at a faster rate than the control one. Following HGF stimulation, hepatocytes from Socs1[superscrip -/-]Ifng[superscript -/-] mice display increased MET signaling, cell migration and proliferation. Forced expression of SOCS1 inhibits HGF-induced signaling pathways in different human or murine hepatoma cell lines. Furthermore, SOCS1 also decreases cell proliferation, anchorage-independent growth, and migration of HCC cell lines in cellulo, and results in significant inhibition of their growth as xenografts in immunodeficient mice. My findings show that activation of HGF-MET signaling results in transcriptional activation of SOCS1 gene, followed a physical interaction between SOCS1 and MET. Analysis of various SOCS1 mutants reveals that this interaction is mediated primarily via the SH2 and the kinase inhibitory region (KIR) domain of SOCS1. MET kinase activity is required for this interaction since SOCS1 binding to a kinase-dead MET mutant is dramatically reduced. MET promotes phosphorylation of SOCS1 on four tyrosine (Tyr) residues. Although these Tyr might represent potential binding sites for adaptors containing phospho-Tyr-binding domains, they do not appear to be involved in the interaction of SOCS1 with MET. I also show that SOCS1 induces polyubiquitination of MET via K48-ubiquitin chain elongation leading to its degradation by proteasomes. The SOCS1-mediated downmodulation of MET expression in HCC cells occurs independently of the Cbl-mediated lysosomal degradation pathway shared by many other RTKs. Taken together, my findings show that SOCS1 attenuates HGF-induced cellular functions by targeting the activated MET receptor for proteasomal degradation.