Nous avons souhaité, dans ce travail de Thèse, préciser le rôle de l’hormone prolactine (PRL) dans la tumorigenèse des prolactinomes. Nous avons tout d’abord décrit l’histoire naturelle et moléculaire des tumeurs lactotropes développées par le modèle de souris Prlr-/-, invalidé de façon globale pour le récepteur de la PRL (PRLR). Les femelles Prlr-/- développent des prolactinomes avec 100% de pénétrance à 12 mois. Ces tumeurs sont très sécrétantes, invasives et prolifératives. L’analyse transcriptomique comparative des hypophyses de souris Prlr+/+ et Prlr-/- nous a permis de mettre en évidence de nouvelles voies de signalisation impliquées dans la survenue de ces tumeurs. Ces nouveaux gènes candidats seront à rechercher chez l’Homme. Par ailleurs, l’étude d’un autre modèle murin développé dans le cadre de ce travail, invalidé de façon spécifique dans la cellule lactotrope, a permis de démontrer pour la première fois in vivo que la PRL exerçait un rétrocontrôle autocrine sur la sécrétion et la prolifération des cellules lactotropes. Bien que nous n’ayons pas retrouvé de mutation germinale du PRLR dans une large cohorte de patients atteints de prolactinome sporadique, nos résultats suggèrent que des mutations somatiques de ce gène ne sont pas à exclure et pourraient contribuer à la survenue de la pathologie humaine. / In this work, we investigated the role of prolactin (PRL) in prolactinoma tumorigenesis. We first described the natural and molecular history of lactotroph cell tumors developed by the Prlr-/- mouse model, globally invalidated for the PRL receptor (PRLR). The Prlr-/- females develop prolactinomas with 100% penetrance at 12 months of age. These tumors are highly secreting, invasive and proliferative. The comparative transcriptomic analysis of pituitaries from Prlr+/+ and Prlr-/- mice suggested new signaling pathways involved in lactotroph adenoma developement in this mouse model. The role of these novel candidate genes remains to be demonstated in Humans. Furthermore, by studying another mouse model developed during this work, deleted for Prlr only in lactotroph cells, we demonstrated for the first time that PRL exerts an autocrine feedback on lactotroph cell secretion and proliferation in vivo. Although we did not find any germline mutation of PRLR in a large cohort of patients with sporadic prolactinoma, our results suggest that somatic mutations of this gene cannot be excluded and may contribute to the onset of the human pathology.

Introduction HNF1B is a tissue-specific transcription factor, which plays a crucial role in the embryological development of a number of organs, especially kidneys, gastrointestinal system, pancreas and billiary system. While the significance of HNF1B in the development of urinary tract malformations has already been well described, its role in the pathogenesis of solid tumors has not yet been elucidated. Based on the current data it seems that depending on the type of individual tumor HNF1B can either act as an oncogene or a tumor suppressor. However, the precise mechanism of how it exerts its influence is still unclear. Aims: The thesis focuses on expanding the knowledge of the significance of HNF1B changes in selected solid tumors and non-neoplastic lesions. The individual goals include: 1) determining the role which HNF1B plays in the pathogenesis of these lesions, 2) evaluating the significance of HNF1B for differential diagnosis, 3) analysis of the prognostic and predictive meaning of HNF1B, 4) mutation analysis of the HNF1B gene in all the tumor and non-tumor tissues with the aim to identify novel pathogenic mutations, 5) methylation analysis of the HNF1B promoter. Material and methods: Immunohistochemical examination with the antibody against HNF1B was performed on 516 samples of tumor and...

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第20055号 / 医博第4163号 / 新制||医||1018(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 山田 泰広, 教授 戸井 雅和, 教授 野田 亮 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

Bone morphogenetic protein 2 (BMP2) is a secreted growth factor that is essential for proper embryonic development and proliferation. Our laboratory discovered a nuclear variant of BMP2 (nBMP2) which is produced when translation is initiated at an alternative start codon within the BMP2 gene. When translation occurs at the downstream start codon, the resulting protein lacks the ER signal peptide, thereby allowing cytoplasmic translation and nuclear localization. Our aim is to distinguish the role of this nuclear localized variant from secreted BMP2. Overexpression of nBMP2 in HEK293 and HT29 cell lines resulted in a higher percentage of cells in proliferative phases of the cell cycle. We determined that nBMP2 does not regulate cell cycle progression by inducing hyperphosphorylation of retinoblastoma protein (Rb), but it may regulate the cell cycle by interacting with ROC1. In order to examine the role of nBMP2 in vivo, we have generated a mouse model in which a mutation of the nuclear localization signal (NLS) disrupts nuclear localization of nBMP2. Aberrant crypts were more abundant in nBmp2NLStm azoxymethane (AOM) treated mice than in wild type mice. Furthermore, H&E staining of colonic tissue showed that mutant mice have increased levels of dysplasia and aberrant crypt foci. This work suggests that nBMP2 is involved in regulating cell cycle progression and proliferation, and therefore may play a role in tumorigenesis.

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Insulin-like growth factor binding proteins (IGFBPs) modulate the bioavailability of IGFs in circulation. IGFBPs 1-6 bind IGFs with high affinity and can either potentiate or inhibit IGF signaling in a context dependent manner. IGFBP2 is a 36 kDa protein and the second most abundant IGFBP in serum. Numerous studies in the recent past have implied a pro-tumorigenic role of IGFBP2. Elevated expression of IGFBP2 has been observed in multiple malignancies, including glioblastoma multiforme (GBM), ovarian, pancreatic, gastric, prostate, colon, breast, thyroid cancer and leukemia. In addition, increased expression of IGFBP2 in both tissues and serum of patients has been correlated with poor prognosis in prostate, glioblastoma and colon cancers. Pro-tumorigenic actions of IGFBP2 have been supported by in vitro studies, where IGFBP2 increases the tumorigenic potential of adrenocortical tumor cells, epidermoid carcinoma cells, glioma cells and ovarian cancer cells. Further, using xenograft animal models, the role of IGFBP2 in the progression of glioma has been established. In breast cancer, IGFBP2 was found to be over expressed in ductal carcinoma in situ and invasive breast cancer samples. IGFBP2 over expression has been shown to confer drug resistance and an increased expression has been reported to correlate with lymph node metastasis in T1 breast carcinomas. These reports implicate IGFBP2 in breast cancer biology. However, its role in breast cancer progression is not well defined. With this background, the following objectives were set for the current study: Functional characterization of IGFBP2 with respect to its possible role in breast cancer progression. Elucidation of the molecular mechanisms of IGFBP2 actions. Towards this, immunohistochemistry was performed on 132 invasive ductal carcinoma (IDC) grade III tumors using IGFBP2 specific antibody. It was observed that IGFBP2 expression was significantly higher in tumors in comparison to normal tissues that showed no detectable staining for IGFBP2. It was also observed that expression of IGFBP2 significantly correlated with the expression of ER. To understand the functional significance of IGFBP2 over expression in breast cancer, IGFBP2 was characterized with respect to proliferation, survival and tumor forming ability (in vitro and in vivo) in BT474 breast cancer cells. The knockdown of IGFBP2 expression resulted in suppression of colony formation (nearly 70%) in these breast cancer cells, which could be partially reversed upon exogenous addition of IGFBP2 protein. Proliferation assays using stable clones with knockdown of IGFBP2 in BT474 cells showed a significant decrease in proliferation as compared to vector transfected cells in the presence of serum. Culturing of IGFBP2 knockdown breast cancer cells in serum free medium resulted in their growth arrest in G0/G1 phase of cell cycle as compared to control cells, which progressed through the cell cycle. Prolonged culturing of IGFBP2 knockdown cells in serum free condition (up to 72 h) resulted in the increase of cells in sub G1 phase of the cell cycle. Prolonged depletion of growth factors (serum free conditions) could result in apoptosis of these G1 arrested IGFBP2 knockdown cells. When serum starved IGFBP2 knockdown cells were treated with IGFBP2 protein, the cells arrested in G0/G1 phase were able to progress through the cell cycle and concomitant decrease in sub G1 fraction was observed. Knockdown of IGFBP2 resulted in significantly decreased number and visibly smaller colonies in anchorage independent conditions in vitro. Consistent with this observation, in vivo tumor xenograft formation with IGFBP2 knockdown cells also showed significant reduction in tumor weight as compared to vector generated tumors. These results imply that IGFBP2 has potent growth promoting effects on breast cancer and acts as a mitogen/survival factor for breast cancer cells. To elucidate the molecular mechanisms underlying the pro-tumorigenic effects of IGFBP2, the transcriptome profile following IGFBP2 perturbation in breast cancer cells was determined. IGFBP2 knockdown resulted in significant changes in the expression of genes associated with cellular proliferation and tumorigenicity. The down regulated genes were found to be associated with several events, notably cell cycle, p53 and Wnt signaling, as revealed by Gene Set Enrichment Analysis (GSEA). To further validate these results in breast cancer tissues, whole genome expression analysis was performed in 19 breast tumor samples which were categorized as IGFBP2 positive or negative based on immunohistochemical staining pattern. In comparison to IGFBP2 negative tumors, IGFBP2 positive tumors showed increased expression of genes belonging to MAPK, focal adhesion and Wnt signaling pathway. In order to identify the genes commonly regulated by IGFBP2 in cell lines and tumors, the gene expression profiles of IGFBP2 positive versus IGFBP2 negative tumors and IGFBP2 knockdown breast cancer cells were compared. 347 genes were found to be common among IGFBP2 regulated genes in tumors and cell line. The most significant networks representing the web of interactions among these genes were found to be associated with cellular growth and proliferation, cellular movement and nucleic acid metabolism, indicating an association of IGFBP2 expression phenotype to the distinct changes in expression of genes associated with the regulation of cellular growth and migration. Silencing of IGFBP2 in BT474 cells resulted in a reduced IGF signaling as evidenced by the reduced phosphorylation of IGF1R and concomitantly that of ERK. This effect could be reversed upon addition of the IGFBP2 protein, implying that IGFBP2 potentiates IGF signaling in breast cancer cells. Besides IGF ligand and their receptors, regulation of proliferation associated genes like CENPF, TOP2A, CCND1 and FOXM1 by IGFBP2 was observed, thus providing a molecular basis for the pro-proliferative effects of IGFBP2 on breast cancer cells. Addition of IGFBP2 to immortal breast cells resulted in reduced IGF1R signaling and reduced pERK and pAKT signaling. Additionally, the genes involved in cellular proliferation were down regulated upon IGFBP2 treatment in immortal cells. IGFBP2 knockdown clones had reduced expression of FOXM1, a key regulator of cell cycle for G1/S and G2/M transition, and M phase progression. The regulation of CENPF and CCND1 genes was established following over expression of FOXM1 in IGFBP2 knockdown cells. One of the important and novel finding of this study is the regulation of Wnt signaling pathway genes such as CCND1, MMP7, FGF18, MYCBP, FN1 and survivin by IGFBP2. In support of this, β-catenin protein was found to be regulated by IGFBP2 in breast cancer and GBM cells, as evidenced by knockdown and over expression studies. Furthermore, regulation of β-catenin by IGFBP2 was found to involve integrin-FAK and IGF1R signaling. Another important finding of this study is the correlation of IGFBP2 over expression with elevated β-catenin levels in breast tumors. When expression of both IGFBP2 and β-catenin was correlated with the lymph node status of breast cancers, a significant association of IGFBP2 and β-catenin staining with increased lymph node metastasis was observed in comparison with tumors that did not show staining for either protein. Altogether, in this study employing genomic, cellular and molecular approaches, a pro- tumorigenic role for IGFBP2 in breast cancer has been established. Furthermore, this study provides novel insights into the molecular mechanisms employed by IGFBP2 involving IGF1R, FAK and Wnt signaling pathways during breast cancer progression.

La protéine multifonctionnelle E4F1 fut initialement identifiée comme une cible de l'oncoprotéine virale E1A au cours de l'infection par l'adénovirus. Nos données, ainsi que celles d'autres laboratoires, montrent qu'E4F1 intervient à de multiples niveaux de régulation de la voie p53, une voie de signalisation très fréquemment inactivée au cours de la tumorigenèse. Au cours de ma thèse, j'ai mis en évidence et caractérisé un nouveau niveau de régulation impliquant la protéine E4F1 et un autre régulateur important de la voie p53 : l'oncoprotéine Mdm2. Mes travaux ont permis de montrer, pour la première fois, qu'E4F1 et Mdm2 sont présents dans un même complexe multiprotéique associé à la chromatine et dont le recrutement est indépendant de p53. La formation du complexe E4F1-Mdm2 est sous la dépendance de certains stress cellulaires, telle que la réponse aux stress oxydatifs. De plus, Mdm2 et E4F1 sont capables de s'ubiquitinyler mutuellement sans promouvoir leur protéolyse. Nos résultats préliminaires suggèrent que ce complexe chromatinien Mdm2-E4F1 est impliqué dans le contrôle d'un programme transcriptionnel apparenté à une réponse au stress oxydatif. L'ensemble de ces données suggère des fonctions de Mdm2 au niveau de la chromatine, indépendantes de sa fonction bien décrite de régulateur du suppresseur de tumeur p53. / E4F1 is a multifunctional protein that was first identified as a cellular target of the viral oncoprotein E1A during adenoviral infection. We, and others, have shown that E4F1 impinges at different level of the p53 pathway, which is frequently inactivated during tumorigenesis. During my PhD, I have highlighted and characterized a novel level of regulation implicating E4F1 and an other key regulator of the p53 pathway: the Mdm2 oncoprotein.My work have shown for the first time that Mdm2 and E4F1 directly interact in a same multiprotein complex associated with chromatin, and this recruitment occurs independently of p53. The Mdm2-E4F1 complex formation is dependant of some cellular stresses, such as oxidative stresses reponses. Our preliminary data also indicate that E4F1 and Mdm2 ubiquitylate each other without promoting their proteolysis, and influence their stability on chromatin. Our preliminary results indicate that this Mdm2-E4F1 chromatinian complex is involved in the regulation of a transcriptional program dependant of oxidative stresses. These data support the notion that Mdm2 presents unexpected functions on chromatin, independently of its very well described p53 regulation.

Les β-arrestines (Arrbs) régulent diverses voies de signalisation dont la voie Wnt/β-caténine (Wnt), un acteur clé dans le cancer colorectal. Le but de mon projet était d'étudier l'implication et les mécanismes régulés par les Arrbs dans la tumorigenèse intestinale dépendante de la voie Wnt. L'inhibition de l'expression des Arrbs partielle ou totale dans des souris ApcΔ14/+ montre que seules les souris invalidées pour l'Arrb2 développent 33% des tumeurs détectées chez les souris ApcΔ14/+ ; Arrb2+/+. Ces tumeurs ont une croissance normale. Cependant, l'analyse de leur transcriptome montre qu'elles expriment notamment certains gènes liés au système immunitaire, alors que les tumeurs dépendantes de l'Arrb2 expriment des gènes différents impliqués entre autres dans la voie Wnt. L'invalidation de l'Arrb2 réduit l'expression de gènes cibles de la voie Wnt dans les cellules isolées de 12 sur 18 tumeurs de souris ApcΔ14/+, et inhibe l'augmentation d'activité Wnt et la formation de colonies en agar mou induite par l'invalidation d'Apc dans des cellules murines ApcMin/+. L'Arrb2 est donc essentielle pour l'initiation et la croissance des tumeurs intestinales présentant une activité Wnt élevée. Pour comprendre les mécanismes régulés par l'Arrb2 dans ce contexte, les complexes protéiques associés à l'Arrb2 ont été analysés par protéomique dans des cellules humaines de cancer colorectal SW480 exprimant ou non un dominant négatif de Tcf4. 132 partenaires de l'Arrb2 potentiellement imbriqués dans un réseau de 917 protéines, ont été identifiés dans les cellules où la voie Wnt est active. Une baisse de 80% de l'activité Wnt entraine la disparition de 41 protéines avec 256 interactions potentielles alors que 42 protéines apparaissent avec 244 interactions potentielles. Le rôle clé d'Arrb2 dans le cancer colorectal s'expliquerait par la connexion d'au moins une quarantaine de protéines dépendantes de l'activité Wnt à un réseau de signalisation complexe dont l'analyse est en cours. / Β-arrestins (Arrbs) participate in the regulation of multiple signaling pathways, including Wnt/β-catenin (Wnt), the major actor in human colorectal cancer. The aim of my project was to study the involvement of Arrbs and the mechanisms they regulate in Wnt-dependent intestinal tumorigenesis. The partial or total inhibition of Arrbs in ApcΔ14/+ mice showed that only mice with Arrb2 depletion developed only 33% of the tumors detected in their Arrb2-WT littermates. These remaining tumors grow normally and are Arrb2–independent. Transcriptomic analysis showed that they overexpressed genes that reflect a high interaction with the immune system, whereas those overexpressed in Arrb2–dependent tumors are predominantly involved in Wnt signaling. Moreover, Arrb2 siRNAs decreased the expression of Wnt target genes in cells isolated from 12 of 18 tumors from ApcΔ14/+ mice, completely reversed the increased Wnt activity and colony formation in soft agar induced by Apc siRNA treatment in ApcMin/+ cells. Therefore, Arrb2 is essential for the initiation and growth of intestinal tumors displaying elevated Wnt pathway activity. To better understand the mechanisms involved in this context, Arrb2 protein complexes were analyzed by a differential systematic proteomic approach in SW480 human colorectal carcinoma cells expressing or not a Tcf4 dominant negative. 132 Arrb2 partners potentially involved in a signaling network of 917 proteins were identified in cells with a high Wnt activity. Upon a 80% decrease of this activity 41 partners disappeared with their 256 potential interactions whereas 42 partners appeared with 244 new possible interactions. Arrb2 key role in colorectal cancer could be explained by the cross-talk of about 40 proteins dependent of Wnt activity with a highly complex signaling network that is currently analyzed.

Le cancer colorectal (CCR) représente un problème majeur de Santé publique. Des facteurs de risque environnementaux, ainsi que l'apparition séquentielle d'altérations génétiques et épigénétiques corrélant avec la progression tumorale ont été extensivement décrites. Cependant, les variations épigénétiques préexistant dans le tissu sain, potentiellement responsables de différences notoires de susceptibilité au CCR, sont restées élusives jusqu'à ce jour. Afin de répondre à cette problématique, la lignée murine Apcd14 (porteuse d'une mutation hétérozygote constitutive au niveau du gène Adenomatous polyposis coli) a servi de modèle au cours de ce projet. Les individus de cette lignée comportent une expressivité très variable, au sens qu'ils développent spontanément un nombre plus ou moins important de tumeurs intestinales, impactant sur leur survie. Cette hétérogénéité est observée en dépit de conditions d'élevage et de génomes considérés identiques. L'analyse exhaustive de cette lignée a conduit à y caractériser deux groupes de souris, présentant une gravité différente de phénotype. La variation d'expression génétique dans le tissu sain (i.e en amont de la tumorigenèse) a ensuite été analysée dans le but de comprendre l'établissement de cette hétérogénéité. Ceci a mené à la découverte d'une signature de gènes différemment exprimés entre les deux groupes, permettant de corréler de façon parfaite données moléculaires et phénotype. La potentielle héritabilité de cette signature a par la suite conduit à remettre en cause le statut considéré syngénique de la lignée. Les approches expérimentales effectuées ont déjà permis de cibler une région chromosomique, ce qui mènera à court terme à la caractérisation d'un nouvel acteur impliqué dans la tumorigenèse intestinale. De manière plus générale, les expériences développées durant ce projet ouvrent la voie à la notion de susceptibilité individuelle face au cancer dépendante de la variation d'expression génétique. / Colorectal cancer (CRC) is a major public health concern. Environmental clues, as well as sequential genetic and epigenetic alterations correlating with tumor progression have been extensively described. Meanwhile, pre-existing epigenetic variations in the healthy intestinal mucosa, potentially leading to differences in CRC suceptibility, have generally been overlooked. In order to answer to this question, we have made use of the Apcd14 mouse model (carrying a heterozygous mutation in the Adenomatous polyposis coli gene). Although all Apcd14 mice apparently share the same genome and are raised in the same environmental conditions, they exhibit a huge phenotypic variability at the individual level, spontaneously developping a few or numerous intestinal tumors, that ultimately results in differences in survival rates. Through detailed analysis of this strain, two groups have been characterized, exhibiting several phenotypic specificities. Gene expression analysis in the healthy intestinal tissue was then performed in order to understand the differences already existing, prior to tumorigenesis. This led to the identification of a group-specific gene expression signature, allowing a correlation between macroscopic phenotype and molecular data. Consideration of the hereditary potential of this signature led to reconsider the syngeneic status of the Apcd14 strain. Several experimental data already targeted a specific genomic region, and this will allow to identify the genetic alteration involved. More generally, this project opens the way to discover a link between individual susceptibility to intestinal tumorigenesis and gene expression variability.