The REarranged in Transfection (RET) tyrosine kinase is an important signalling protein for the development of neural crest-derived tissues such as the enteric and sympathetic nervous systems. RET is constitutively activated in multiple human tumour types, such as thyroid carcinomas and some non-small cell lung cancers. RET has 3 distinct isoforms, RET9, RET43 and RET51, which are named after the lengths of their unique C-terminal tails. Here, we investigate the role of RET in the TT thyroid carcinoma cell line, where it is a driver of tumourigenesis, and in the MiaPaCa-2 pancreatic carcinoma cell line, where RET is not driving tumour initiation, but may nonetheless have a profound effect on tumour progression. We generated lentiviral constructs for shRNAs that target either RET9 or RET51 specifically, or a common region shared by all RET isoforms. TT and MiaPaCa-2 cells were transduced using these lentiviral particles to create stable cell lines containing knockdowns of total RET, RET9, or RET51. Using a variety of morphological and biochemical assays, we found that RET expression is critical for TT cell survival, and that both RET9 and RET51 play significant roles in driving cell proliferation in TT cells. Conversely, RET is not critical for MiaPaCa-2 cell survival, and RET knockdown had no effect on MiaPaCa-2 proliferation. MiaPaCa-2 cells instead underwent dramatic morphological changes, from their normal spindle-like mesenchymal appearance to an increasingly flattened and epithelioid character, in response to RET9, RET51 or total-RET knockdown. The observed morphological changes were coupled with significantly reduced invasiveness through matrigel towards a source of chemoattractant, suggesting a critical role for RET in mediating cell invasiveness. These results suggest that RET may not only drive tumourigenesis, but can also enhance disease progression when expressed in other tumour types. We predict that RET may play critical roles in perineural invasion in pancreatic cancers, a process where cells invade along peripheral nerve fibers by following an increasing concentration of chemoattractants secreted by nerve and glial cells. Thus, RET may be a valuable target to slow, or stop this process, which would have significant clinical implications in a wide variety of cancers. / Thesis (Master, Pathology & Molecular Medicine) -- Queen's University, 2013-08-30 11:45:41.969

Le cancer colorectal est issu des cellules de l’épithélium et se définit comme une pathologie induite par une accumulation d’altérations génétiques. Des mutations de type gain-de-fonction dans les gènes KRAS, NRAS et BRAF sont retrouvées dans plus de 60% des cancers colorectaux entraînant potentiellement l’activation constitutive de la signalisation en aval, notamment le sentier MEK/ERK. Dans cette thèse, nous avons évalué les mécanismes moléculaires par lesquels l'activation du sentier MEK/ERK régularise la différenciation épithéliale et la tumorigénèse intestinale. Dans les cellules épithéliales intestinales (CEIs), nos résultats montrent que les kinases ERK1/2 doivent être inactivées pour permettre l’induction du processus de différenciation entérocytaire. En effet, l'expression d’une forme constitutive active de MEK1 (caMEK1) est suffisante pour bloquer la différenciation tant morphologique que fonctionnelle. Une augmentation de la phosphorylation du facteur de transcription Cdx2 sur la sérine 60, qui diminue son activité transcriptionnelle, constituerait un des mécanismes impliqués. Dans des cellules cryptales intestinales indifférenciées, l’expression du caMEK1 induit une transition épithélium-mésenchyme (EMT), un processus associé au cancer colorectal. Cette EMT confère aux CEIs des capacités invasives et métastatiques in vivo associées à la sécrétion de protéases extracellulaires (MMP2/9). Nous avons identifié plusieurs autres cibles moléculaires de l’activité MEK/ERK impliquées dans l’EMT et l’invasion tumorale. Nous avons démontré l’implication des cascades Fra-1/Snail2 et EGR-1/Snail1 dans la répression transcriptionnelle de la E-cadhérine, une étape clé de l’EMT. Ce mécanisme de répression est également présent dans les lignées cancéreuses colorectales humaines possédant la mutation oncogénique de KRAS. L’analyse comparative par micropuce d'ADN Affymetrix dans les CEIs transformées par caMEK1 a permis d’identifier le gène encodant pour la serpineE2, un inhibiteur de protéases, comme le gène le plus fortement induit. Nous avons démontré que la serpineE2 est une cible moléculaire directe de l'activité oncogénique de la voie KRAS/BRAF/MEK/ERK et démontré son importance dans la migration et l’invasion tumorale par l'utilisation d'ARN interférents. On observe d’ailleurs une très forte expression de la serpineE2 dans des tumeurs colorectales humaines en comparaison à la marge saine adjacente. Nous avons aussi démontré que la transformation des CEIs induite par l’expression des formes actives de KRAS ou de MEK1 stimule la voie signalisation Wnt/β-caténine, dont la fréquente dérégulation constitue un évènement majeur menant au développement du cancer du côlon. La phosphorylation MEK-dépendante de LRP6 (S1490/T1572) semble être responsable de l’augmentation de l’activité transcriptionnelle de la β-caténine, associée à une augmentation de sa présence au noyau. Cette interconnexion entre les voies KRAS/MAP kinase et Wnt/β-caténine a également été observée dans des cellules cancéreuses colorectales humaines mutées pour KRAS ou BRAF. Finalement, une augmentation du niveau de phosphorylation de LRP6 a été observée dans les adénomes et tumeurs colorectales humaines, supportant l’idée que la phosphorylation de LRP6 puisse être impliquée dans la progression tumorale.

High grade astrocytomas are very progressive brain tumors. Glioblastoma multiforme is the most frequent and the most malignant type with very infiltrative phenotype of the tumor cells. Fibroblast activation protein FAP is a predominantly membrane bound prolyl peptidase bearing exo- and endopeptidase hydrolytic activities. FAP is known to play a role in wound healing, cell migration and invasion and its expression is linked to the pathogenesis of several malignancies. mRNA expression of FAP is upregulated in 48% of glioblastomas according to The Cancer Genome Atlas microarray data. The involvement of FAP in the pathogenesis of astrocytic tumors is largely unknown. The aims of this work are to analyse the expression of FAP in primary cell cultures derived from high grade gliomas and to analyse the influence of FAP on the growth, migration and invasion of glioma cells. Our ELISA and western blot results showed heterogenous expression of FAP in the studied glioma primary cell cultures and cell lines. Both enzymatic activities characteristic of FAP were detected in the primary glioma cell culture P11 with high expression of FAP. In these cells, FAP was present not only in the typical plasma membrane localization, but also in the cytoplasm as demonstrated by immunofluorescence staining. The P11 cells...

Auf dem Weg vom Primärtumor zur systemischen Metastasierung, der Haupttodesursache von Krebserkrankungen, ist die Einzelzellmigration von Tumorzellen durch dreidimensionales Bindegewebe ein entscheidender Schritt. Die vorliegende Arbeit zeigt Untersuchungen zur Tumorzellmigration und –plastizität in einem 3D-Migrationsmodell. Kleine G-Proteine kontrollieren Zytoskelettfunktionen, insbesondere Aktinpolymerisation und die Bildung von Zellprotrusionen durch Rac sowie Actomyosinkontraktion durch Rho. Durch pharmakologische Inhibitoren von Rac und dem Rho-Effektor ROCK soll deren Bedeutung für Einzelzellmigration in einem dreidimensionalen Modell und vor allem der Effekt auf Morphologie, Plastizität und Migration von Tumorzellen geklärt werden. Nach Inhibition von ROCK zeigen hochinvasive HT1080 Fibrosarkomzellen einen multipolar-dendritischen und sessilen Phänotyp. Nach Hemmung von Rac wird hingegen ein rundlicher, aber ebenfalls apolarer und sessiler Phänotyp induziert. Bei simultaner Inhibition von Rac und ROCK entstehen rundliche, apolare, sessile Zellen mit abortiven Pseudopodien. Wird das Gleichgewicht von Rac und ROCK durch konstitutive Aktivierung von ROCK gestört, so entsteht eine zweigeteilte Population, bestehend aus rundlichen Zellen, die Blebs bilden, und langgezogenen Zellen. Nach Sortierung nach ihrem ß1-Integrinexpressionsniveau zeigten Zellen mit niedriger Integrin-Expression einen rundlichen Migrationstyp mit blasenartigen dynamischen Protrusionen, während Zellen mit hoher Integrin-Expression langgezogen-mesenchymal migrierten. Somit steuern ROCK und Rac gemeinsam und zeitgleich die mesenchymale Einzelzellmigration. Während Rac Protrusion vermittelt, ist ROCK für Kontraktilität und Retraktion verantwortlich. Erst durch Koordination von Rac und Rho/ROCK entsteht somit Polarität und 3D mesenchymale Migration. / In the development from a primary tumor to metastatic dissemintation, which is the main cause of death from cancer, single cell migration through three-dimensional tumor stroma is an essential step. This work presents data concerning tumor cell migration and plasticity in a three-dimensional migration model. Small G-proteins control cytosceletal functions, especially actin polymerisation and the formation of cell protrusions through Rac as well as actomyosin contractility through Rho. Using pharmacological inhibitors of Rac and the Rho effector ROCK their impact on single-cell-migration in a three-dimensional model and particularly on morphology and plasticity of migration of tumor cells should be clarified. After inhibition of ROCK highly invasive HT1080 fibrosarcoma cells show a multipolar-dendritic and sessile phenotype. Inhibtion of Rac however induced a rounded phenotype which was also apolar and sessile. Simultaneous inhibition of ROCK and Rac resulted in rounded, apolar, sessile cells with abortive pseudopods. After disturbing the balance of ROCK and Rac by constitutive activation of ROCK, a divided population of cells developed, consisting of rounded, blebby cells and elongated cells. After sorting the cells according to their level of ß1-integrin expression, cells with low expression of integrins adopted a rounded type of migration with blebby dynamic protrusions, whereas cells with high integrin expression migrated in a elongated-mesenchymal way. Thus ROCK and Rac control together and simultaneously mesenchymal single cell migration. While Rac mediates protrusion, ROCK is responsible for contractility and retraction. Consequently only by coordination of Rho/ROCK and Rac polarity and mesenchymal 3D migration becomes possible.

Thesis advisor: Marc-Jan Gubbels / Toxoplasma gondii – an obligate intracellular parasite – has a complex multistep mechanism for host cell invasion with a pivotal role played by calcium signaling. However, the coordination amongst the players in all the key steps of this signaling pathway, essential for parasitic life cycle of Toxoplasma, is still not entirely known. Given the evolutionary relationship between ciliates and apicomplexans, this work evaluates the functions of three orthologous proteins in cell signaling of alveolates leading to calcium-dependent exocytosis of vesicles such as trichocysts and micronemes. The proteins investigated are calmodulin (CaM) which is a calcium sensor, calcineurin (CN), a protein phosphatase, and parafusin-related protein 1 (PRP1), the Toxoplasma ortholog of ciliate protein parafusin. In the ciliate, CaM activates CN upon rise in intracellular calcium. Activated CN then leads to the dephosphorylation of the secretory vesicle scaffolding protein called parafusin. Parafusin dephosphorylation dissociates it from the calcium-dependent secretory vesicles, which then discharge their contents. As expected upon conditional depletion, we found CaM to be essential for Toxoplasma tachyzoites and CN to be significant for the lytic cycle. Surprisingly, the microneme secretion remained normal in the CN depleted parasites, although there was significant reduction in the attachment of the parasite to the host cell. We also found that PRP1 is dispensable for Toxoplasma lytic cycle, despite its absence affecting the microneme secretion induced by the calcium ionophore, A23187. However the secretion defect is not uniform and remains comparable to the wild type when it is induced using other pharmacological agents like ethanol, zaprinast and propranolol. Therefore despite phylogenetic conservation of the three proteins in alveolates, this work demonstrates their involvement in distinct functional aspects in Toxoplasma compared to other ciliates. Alongside the limited understanding of the molecular mechanism, our knowledge about the cellular sensors in Toxoplasma is also scarce. Our laboratory has previously identified a double C2 (DOC2) domain containing protein called TgDOC2 and demonstrated its role in overall microneme secretion. However, TgDOC2 does not regulate the dosed microneme release associated with varied steps of the egress-invasion trajectory. In general, DOC2 domain containing proteins work in coordination with each other to execute their cellular function, mostly in calcium-dependent manner. We therefore, wanted to expand our knowledge of this domain containing proteins in the parasite. In this work, we investigated a conserved apicomplexan protein called FER2 containing multiple DOC2 domains. Conditional depletion of FER2 appeared detrimental due to significant loss of invasion and attachment of the parasites. FER2 depleted parasites have normal microneme secretion, which is currently the only known calcium-dependent secretory organelle in Toxoplasma, but abrogated the release of rhoptries, the second secretory organelle to be released during invasion. Altogether this work extends the importance of calcium signaling in Toxoplasma gondii and brings into light the novel aspects of some parasitic proteins which are significant in reconstructing our understanding of the signaling pathway in this parasite. / Thesis (PhD) — Boston College, 2016. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Biology.

Endophytic fungi live within tissues of plant hosts without causing symptoms of disease. These fungi are broadly split into the taxonomically and ecologically cohesive Clavicipitaceous endophytes, which infect grasses, and the taxonomically diverse non-Clavicipitaceous endophytes, which are found in nearly all plants and have diverse ecological strategies. My dissertation has two sections: Section A investigates the intersection of Clavicipitaceous endophyte ecology with other ecological theory, including invasion ecology (Chapter II) and community ecology and climate change (Chapter III); Section B investigates the ecology of one group of non-Clavicipitaceous endophytes, the Xylariaceae, using a culture-based study in Ecuador (Chapter IV) and a next-generation sequencing based endophyte survey in Taiwan (Chapter V). Section B is centered on testing the Foraging Ascomycete (FA) hypothesis—the idea that some decomposer fungi may adapt an endophytic lifestyle to escape limitations in primary substrate in both time and space. In Chapter II, I utilized a host-specific Epichloë endophyte present ubiquitously in the European native range of the Pacific Northwest (PNW) invasive grass Brachypodium sylvaticum to test theories of invasion. In Chapter III, I examined the grass Agrostis capillaris in the context of a climate manipulation experiment in prairies in the PNW to elucidate patterns of interaction between multiple symbionts (Epichloë endophytes, dark septate root endophytes, and arbuscular mycorrhizal fungi) within single hosts across climatic variation. In Chapter IV, I began to test the FA hypothesis by examining spatial relationships of Xylaria endophytic fungi in the forest canopy with Xylaria decomposer fungi on the forest floor in a remote Ecuadorian cloud forest. In Chapter V, I build on the results from the previous study, using a novel technique to examine spatial ecology of the Xylariaceae, pairing traditional mycological collection with the preparation of a next-generation sequencing metabarcode library of endophytes over a much greater area. This dissertation includes previously published and unpublished coauthored material.

Severe malaria caused by Plasmodium falciparum (P. falciparum) remains a leading cause of death in many low and middle income countries. The intraerythrocytic reproduction cycle of the parasite is responsible for all the symptoms and mortality of malaria. The merozoite, first invade a red blood cell (RBC) in the circulation, then grows, develops and multiplies within it by clonal division. Merozoite invasion is a complex process involving dynamic interactions between ligands in the merozoite coat and receptors on the red blood cell membrane. Therefore, filming the complete malaria invasion processes may shed the light on its mechanism. The rationale of this work is that learning how the various ligand-receptor interactions affect invasion phenotypes will lead us to a better understanding of the key biological and biophysical aspects of parasite growth in the blood. The work described has firstly involved the development of an optimised imaging platform for recording egress-invasion sequences. I used live cell microscopy to understand this stage of malarial infection better, by monitoring egress-invasion sequences in live cultures under controlled conditions and addressing the morphology and kinetics of erythrocyte invasion by P. falciparum. In addition, the erythrocyte invasion phenotypes of the various P. falciparum strains were systematically investigated for the first time by live cell microscopy. Furthermore, to better understand genetic recombination affecting erythrocyte invasion phenotypes, progeny from the 7G8 x GB4 cross was compared to their parents. In order to investigate specific receptor-ligand interactions and their distinct functional characterisations at each distinct stage, the enzymes that cleave receptors on the erythrocytes and antibodies targeting ligands on the merozoites were studied and their effects observed using the live-imaging platform. In the results, the functions of ligands on the merozoites demonstrated for the first time distinct and sequential functions of proteins during erythrocyte invasion, which could potentially guide the design of more effective malaria vaccines. In addition, I have designed microfluidic devices for studying blood stage malaria. Polydimethylsiloxane (PDMS) microfluidic devices are optically transparent, non-toxic and have biocompatible features. Building on previous work, I made specific microfluidic devices for achieving a high throughput of egress-invasion observations. Infected red blood cells were delivered into a microfluidic device channel containing cage-like "nests". The nests were designed to selectively trap these stiff, egress-ready cells, in order to obtain streams of merozoites on maturation. Uninfected RBCs were delivered from another input into a long serpentine channel co-flowing with the egressed merozoites. The results indicated that, during P. falciparum erythrocyte invasion under flow conditions, the morphological effect on erythrocytes and the kinetic properties show significant differences to those in static conditions. In addition, with optimised flow rates, it is possible to reach higher throughput of egress-invasion observations than static conditions. Both the static and flow experiments carried out in this study highlight important mechanisms and processes of malaria invasion, and represent new ways of studying blood stage malaria. Precise and high throughout recording of single-event host-pathogen interaction events will allow us to address a new area of fundamental biological questions in future work.

Abstract Glioblastomas, primary brain tumors, represent a tumor entity with a dismal prognosis and a median survival of only about one year. Invasion into the healthy brain parenchyma contributes substantially to the malignancy of this type of brain tumor. Therefore, a better understanding of the mechanisms promoting the invasive behavior of these brain tumors is needed to identify new therapeutic targets. Cofilin, an actin regulatory protein, has been shown to be an important regulator of the invasive behavior of tumor cells in other types of cancer and the actin cytoskeleton is involved in the formation of a variety of cellular structures important for cell migration and invasion. Cofilin is regulated by phosphorylation on a single residue, serine 3. The aim of this thesis was to examine the role of the cofilin regulatory phosphatase chronophin for glioma cell migration and invasion. First, it was established that chronophin depletion in the cell line GBM6840 leads to an increase in the ratio of phosphorylated cofilin to total cofilin. Higher chronophin levels were correlated with a decrease in F-actin in the cell lines GBM6840 and U87 as measured in an actin spin down assay and in a flow cytometry based assay. Furthermore, it was shown that knockdown of chronophin in two different cell lines, GBM6840 and DBTRG-05-MG, strongly increased their invasiveness in vitro. Expression of human chronophin in the cell line U87 decreased its invasiveness substantially. There was no difference in cell proliferation between GBM6840 and DBTRG-05-MG cells expressing a chronophin targeting shRNA or a control shRNA and U87 cells transfected with an empty vector or a human chronophin encoding plasmid. The increase in invasiveness after chronophin depletion could be correlated with an increase in directionality in cell migration under 2D culture conditions in the cell lines U87 and GBM6840. Moreover, treatment with the ROCK inhibitor Y-27632 decreased directionality in GBM6840 cells under 2D culture conditions and reduced the invasiveness of GBM6840 chronophin shRNA cells back to control levels. Expression of a non-phosphorylatable cofilin mutant, the S3A mutant, was able to reduce invasiveness and to reduce directionality under 2D culture conditions back to control levels in GBM6840 chronophin shRNA cells. This provides important evidence for the involvement of cofilin phosphoregulation in the phenotypes described above. In vivo, when injected into NOD-SCID mice, chronophin depleted cells showed a dramatic growth reduction as compared to control and rescue cells. Transciptomic characterization of GBM6840 cells by microarray analysis and subsequent comparison of the data with microarray profiles of normal brain tissues and different glioma entities identified two specifically chronophin regulated transcripts potentially involved in tumor progression and invasion, MXI1 and EDIL3. Moreover, c-myc was identified as a significantly altered transcription factor after chronophin deregulation based on the number of c-myc target molecules in the microarray dataset. MXI1 is a potential negative regulator of c-myc dependent transcription, and was strongly downregulated after chronophin knockdown in GBM6840. In line with this, the activity of a c-myc reporter plasmid was increased after chronophin depletion in GBM6840 and reduced after chronophin expression in U87 cells. However, the protein level of the c-myc protein was reduced after chronophin depletion in GBM6840. Finally, anaylsis of the expression of proteases known to be important for glioblastoma pathogenesis revealed no major changes in protease expression between chronophin depleted and control cells. Therefore, a comprehensive analysis of chronophin in the context of glioma pathogenesis has been performed in this thesis. It has been shown that chronophin depletion strongly enhanced invasiveness of glioma cells and that it induced transcriptomic changes potentially involved in tumor progression. The proteins regulating cofilin phosphorylation are therefore valuable therapeutic targets for anti-invasive therapy in glioblastomas. Inhibitors for kinases upstream of cofilin, e.g. LIMKs and ROCKs, are available, and might be promising agents for anti-invasive therapy. / Zusammenfassung Glioblastome sind primäre Gehirntumore, die eine besonders schlechte Prognose besitzen und bei denen die mediane Überlebenszeit nur ca. ein Jahr beträgt. Zur Malignität dieses Tumortyps trägt entscheidend das Eindringen der Tumorzellen in das gesunde Hirnparenchym bei. Daher ist es notwendig die molekularen Mechanismen zu verstehen, die diesem Phänomen zu Grunde liegen, um neue therapeutische Zielmoleküle zu identifizieren. Cofilin, ein Protein das das Aktinzytoskellet reguliert, ist in anderen Krebsarten als wichtiger Regulator des invasiven Verhaltens von Zellen bekannt und das Aktinzytoskellet ist an der Bildung einer Vielzahl von zellulären Strukturen beteiligt, die wichtig für die Zellmigration und –invasion sind. Cofilin wird über die Phosphorylierung einer einzigen Aminosäure, des Serin 3, reguliert. Das Ziel dieser Arbeit war es, die Rolle der Cofilin regulatorischen Phosphatase Chronophin für Zellmigration und -invasion zu untersuchen. Zuerst konnte gezeigt werden, dass eine Chronophin Depletion in der Zelllinie GBM6840 zu einer Zunahme des Anteils von P-Cofilin am Gesamtcofilin führt. Ebenso war ein hohes Chronophin Level in den Zelllinien GBM6840 und U87 mit einer Abnahme des F-Actin Levels korreliert, was in einem Aktin spin down Assay als auch mittels Durchflusszytrometrie gemessen werden konnte. Es konnte weiter gezeigt werden, dass eine shRNA vermittelte Depletion des Chronphin zu einer starken Zunahme der Invasivität in den Zelllinien GBM6840 und DBTRG-05-MG in vitro führt. Chronophin Expression in der Zelllinie U87 führte zu einer starken Abnahme der Invasivität. Es gab hingegen keinen Chronophin abhängigen Unterschied in der Proliferation von GBM6840 und DBTRG-05-MG Zellen, die entweder eine Kontroll- oder eine Chronophin gerichtete shRNA exprimierten, sowie keinen zwischen U87 Zellen, die mit einem Leervektor oder einem Chronophin codierenden Konstrukt transfiziert worden waren. Die Zunahme der Invasion nach Chronophin Depletion konnte mit einer Zunahme der Direktionalität der Zellen bei der Migration in einer 2D Umgebung korreliert werden. Desweiteren konnte durch Behandlung mit dem ROCK-Inhibitor Y-27632 in GBM6840 Zellen eine Erniedrigung der Direktionalität bei der Migration in 2D Kultur ebenso erreicht werden, wie eine Reduktion der Invasivität von Chronophin shRNA exprimierenden GBM6840 Zellen auf Kontrollniveau. Die Expression einer nicht-phosphorylierbaren Cofilin Mutante, der S3A Mutante, erniedrigte sowohl die Direktionalität in der 2D Migration als auch die Invasivität von GBM6840 Chronophin shRNA exprimierenden Zellen zurück auf Kontrollniveau. Diese Experimente lieferten wichtige Hinweise darauf, dass die Phosphoregulation von Cofilin ursächlich an der Entstehung der Phänotypen beteiligt war, die nach Chronophin Knockdown beobachtet wurden. In vivo konnte nach Injektion in NOD-SCID Mäuse eine dramatische Wachstumsreduktion der Chronophin depletierten Zellen gemessen werden. Durch Charakterisierung des Transkriptoms der Zelllinie GBM6840 mittels Microarrays und nachfolgender Vergleich der Ergebnisse mit Microarray-Profilen von Normalhirngewebe und verschiedenen Gliomentitäten konnten zwei spezifisch Chronophin abhängig regulierte Transkripte identifiziert werden, MXI1 und EDIL3, die potentiell mit der Progression und Invasivität von Gliomen verknüpft sind. MXI1, ein potentieller negativer Regulator der c-myc abhängigen Transkription, war nach Chronophin Herunterregulation in GBM6840 stark herunterreguliert. In Übereinstimmung mit diesem Befund war die Aktiviät eines c-myc Reporterplasmids nach Chronophin Herunterregulation in GBM6840 erhöht, nach Chronophin Expression in U87 jedoch erniedrigt. Das c-myc Protein selbst wies eine deutliche Reduktion nach Chronophin Depletion in GBM6840 auf. Abschließend wurde die Expression von Proteasen untersucht, für die eine Rolle in der Gliominvasion bekannt ist. Hier wurden jedoch keine größeren Chronophin abhängigen Expressionsunterschiede gefunden. Zusammenfassend gesagt konnte eine umfassende Charakterisierung der Rolle des Chronophin in der Gliompathogenese erreicht werden. Zum einen konnte gezeigt werden, dass Chronophin ein äußerst wichtiger Regulator der Invasion ist, zum anderen dass es zu Chronophin abhängigen transkriptomischen Veränderungen kommt, die potentiell zur Malignisierung des Tumors beitragen. Daher sind die Proteine die die Cofilinphosphorylierung regulieren potentielle therapeutische Zielmoleküle für eine anti-invasive Therapie im Glioblastom. Inhibitoren für die Kinasen, die Regulatoren des Cofilin sind, die ROCK- und LIM-Kinasen, sind verfügbar und stellen möglicherweise vielversprechende Substanzen für die anti-invasive Therapie dar.

An essential event during early pregnancy is the invasion of trophoblasts into the maternal decidua, which is necessary for proper implantation and establishment of maternal-fetal interface and ultimately allows for proper nutrient exchange and immunological tolerance of the growing fetus. For this invasion to occur, cells originating from the trophectoderm undergo an epithelial to mesenchymal transition to become invasive extravillous trophoblasts and begin invading the uterine decidual tissue. Through the secretion of matrix metalloproteinases and through interactions with many cytokines and cell-adhesion molecules, this well-orchestrated process of trophoblast invasion results in extensive remodeling of the maternal spiral vasculature by the extravillous trophoblasts. Ultimately, the spiral arteries are transformed from high resistance, low flow vessels to low resistance, high flow vessels to allow for adequate perfusion of the placenta and developing fetus. Preeclampsia is a leading cause of maternal morbidity worldwide and is associated with the onset of hypertension and proteinuria, typically after 20 weeks of gestation. While the hypertension typically resolves following delivery of the fetus and placenta, both the mother and growing child are faced with long-term adverse health effects such as the development of cardiovascular disease and metabolic disorders. Preeclampsia is characterized by widespread maternal inflammation and endothelial dysfunction triggered by the secretion of soluble factors from the placenta into the maternal circulation. It is thought that the onset of these adverse systemic conditions is initiated by poor placental perfusion and pathologically hypoxic conditions in the placenta. In many cases of preeclampsia, there is evidence of shallow trophoblast invasion which results in incomplete spiral artery transformation, ultimately leading to poor placental perfusion. However, the exact mechanisms underlying the inadequate extravillous trophoblast invasion and remodeling are incompletely understood. LIN28 is an RNA binding protein that is highly expressed in embryonic stem cells, fetal tissues and many cancers, and was discovered as a regulator of the maturation of the Let-7 family of miRNAs. However, as an RNA binding protein, LIN28 has been shown to interact with thousands of mRNA transcripts, leading to both increased and decreased protein expression, and control of many cellular processes such as differentiation, proliferation, migration, invasion, and cellular metabolism. In vertebrates, LIN28 exists as two highly homologous paralogs, LIN28A and LIN28B, however LIN28B is slightly larger and contains a nuclear localization signal not found in LIN28A. While they both function to inhibit Let-7 maturation, there is evidence to suggest they also have independent functions. Given the primary role of LIN28A and LIN28B in modulating cell metabolism, differentiation and invasion, we hypothesized that LIN28A and/or LIN28B regulates trophoblast differentiation and invasion, and that its dysregulation may contribute to preeclampsia. We found that LIN28B mRNA expression is ~1300-fold higher than LIN28A in human term placenta and is the predominant paralog expressed in human primary cytotrophoblasts, syncytiotrophoblasts, and decidual cells. We also found that LIN28B mRNA and protein levels are significantly reduced in human placentas from preeclamptic pregnancies compared to placentas from normal pregnancies, while LIN28A expression is unchanged. Upon investigation of human first trimester placenta sections, we found that LIN28B is more highly expressed in the invasive extravillous trophoblasts and syncytial sprouts compared to villous trophoblasts. To support this with in vitro evidence, we found that overexpression of LIN28B in human HTR8/SVneo cells resulted in increased proliferation, migration and invasion, while knockdown of LIN28B in JEG3 cells resulted in decreased proliferation. Furthermore, knockdown of LIN28B in JEG3 cells led to decreased expression of SYN-1, ELABELA, and the chromosome 19 miRNA cluster, with accompanying increases in the pro-inflammatory cytokine TNFα and ITGβ4, an integrin enriched on non-invasive trophoblasts. Moreover, culture of JEG3 and BEWO cells in hypoxia resulted in significantly decreased levels of LIN28B mRNA and protein expression, as well as syncytin-1 and ELABELA mRNA levels, while TNFα was increased. These results provide the first evidence that LIN28B is the predominant paralog expressed in human placenta and decreased LIN28B may play a crucial role in PE pathogenesis by reducing trophoblast invasion, syncytialization and by promoting inflammation.

Les infections génitales par les virus du papillome humains (HPV) sont les infections virales sexuellement transmises, les plus communes chez les femmes en âge de procréer. Il est désormais bien établi que l’infection persistante par les HPV classés «à haut risque» est l’un des facteurs indispensables au développement de lésions précancéreuses et cancéreuses du col de l’utérus. Ces HPV semblent aussi être impliqués dans le développement d’autres cancers de la région ano-génitale et pourraient être également impliqués dans les cancers de la tête et du cou. Durant cette dernière décennie, des études croissantes tendent à établir un rôle étiologique des HPV dans les dysfonctionnements gestationnels. La détection des ADN HPV dans les placentas issus d’avortements spontanés et leur capacité exceptionnelle à se répliquer in vitro dans les cellules trophoblastiques cultivées en monocouche, ont apporté de nouvelles perspectives quant à la possibilité que le placenta pourrait constituer aussi un tropisme naturel des infections par HPV. Six jours après la fécondation et suite à l’accolement du blastocyste à l’épithélium utérin, le trophoblaste s’engage dans des processus actifs de prolifération, d’invasion et de différenciation complexe pour la construction de l’interface physiologique indispensable aux échanges essentiels entre la mère et l’enfant ; le placenta. De façon intéressante, ses propriétés sont similaires à celles de la cellule tumorale maligne. Néanmoins, ses mécanismes sont étroitement régulés dans le trophoblaste, à la fois dans l’espace et le temps, assurant un développement normal à chaque étape de la grossesse. Devant toutes ces données, nous avions émis l’hypothèse que l’expression des protéines précoces E5, E6 et E7 d’HPV de type 16 (de haut risque), pourraient modifier le développement des trophoblastes infectés. Les résultats obtenus durant ce travail de doctorat démontrent que la protéine virale E5, hautement hydrophobe, est cytotoxique et affecte la viabilité du trophoblaste. Cette cytotoxicité est neutralisée, et la viabilité est améliorée, lorsque les oncoprotéines majeures E6 et E7 sont exprimées en présence de la protéine E5. Lorsque toutes les protéines précoces sont exprimées sous le contrôle de leur propre promoteur (LCR), la viabilité est favorisée. Ces observations ont été confirmées dans les cellules cervicales également. Il a été précédemment rapporté que les oncoprotéines E6 et E7 affectaient l’adhésion du trophoblaste aux cellules endométriales. Dans le présent travail, il a été retrouvé que la protéine E5 diminuait elle aussi l’adhésion, non seulement aux cellules endométriales, mais aussi au support de culture cellulaire. Les capacités de migration et d’invasion de la matrice extracellulaire sont augmentées par l’expression de E5 et dans une plus large proportion par l’expression de E6 et E7. Des résultats similaires ont été obtenus lorsque toutes les protéines de la région précoces sont exprimées sous le contrôle de leur propre promoteur (LCR). La diminution de l’expression de la E-cadhérine est considérée comme un marqueur de malignité et de mauvais pronostic pour les cancers. Nous avons démontré que l’expression de E5, E6 ou de E7, inhibait l’expression de la E-cadhérine, reflétant l’impact des oncoprotéines du virus HPV-16 sur la diminution de l’adhésion et l’augmentation du pouvoir invasif des cellules trophoblastiques. L’investigation d’autres marqueurs de malignité et de tolérance immunitaire, l’étude de l’impact du virus HPV-6 (de bas risque) sur la migration et l’invasion des cellules trophoblastiques, et l’étude de la capacité des protéines précoces d’HPV-16 à influencer l’entrée des particules virales, ont fait l’objet de résultats préliminaires, ouvrant de larges perspectives. Genital Human Papillomavirus (HPV) infections are the most common sexually transmitted infections amongst women on the age of reproduction. It is well established that persistent infection with high-risk HPVs is the necessary factor in the causation of precancerous and cancerous cervical lesions. High-risk HPVs have also been reported to be involved in the causation of head and neck cancers and other anogenital cancers. On this last decade, growing data are attempting to study the potential etiological association of HPV with gestational dysfunctions. The detection of HPV DNA in placentas resulting from spontaneous abortions and the unique ability of multiple HPV types to replicate in vitro in trophoblastic cells cultured in a monolayer system, rise new questions over the HPV tropism. Six days following fertilization and once the apposition of the blastocyst on the uterine wall takes place, the trophoblast, in a very active and complex process, starts to proliferate, invade and to differentiate in order to build a physiological interface; the placenta, from where multiple mother/foetus exchanges occur. Interestingly, the way that the trophoblast behaves is very similar to malignant tumoural cells. However, the trophoblast obeys to strict spatial-temporal regulatory confines, insuring a proper development all along the pregnancy. In regard to these data, we hypothesised that the expression of the high-risk HPV type 16 oncoproteins E5, E6 and E7, might modify the development of the infected trophoblast. During my Ph.D study, I demonstrated that the highly hydrophobic protein E5 is localized in many interne membranes compartments of the transfected trophoblast. E5 affects the viability of transiently and stably transfected trophoblastic cells. E6 and E7, favouring cell growth, neutralised the E5 cytotoxic effect. All HPV-16 early proteins, when expressed under the control of their endogenous promoter (LCR), favoured trophoblastic growth. These observations were also observed in cervical cell lines. In addition, E5 decreased the adhesiveness of trophoblastic cells to the tissue culture plastic and to endometrial cells similarly as previously described for E6 and E7. Cells expressing E6, E7 and in less extend E5 favoured chemotaxic migration and matrigel invasion compared to the cells expressing the LacZ control. These effects were also observed when early proteins were expressed under the control of their own viral promoter (LCR). Interestingly, the E-cadherin was down regulated in trophoblastic cells expressing E5, E6 and E7. In conclusion, HPV-16 early proteins enhanced trophoblastic growth and intensify the malignant phenotype by impairing cell adhesion leading to increased cellular motile and invasive properties. HPV-16 E5 participated, with E6 and E7, in these changes by impairing E-cadherin expression, a hallmark of malignant progression. Additional preliminary results consisting on the investigation of other markers of malignancy and immune tolerance, on studying the impact of the low-risk HPV type 6 early proteins on the migratory and invasive properties of trophoblastic cells and on the study of the ability of HPV-16 to influence the entry of virus particules, allowed to open wide perspectives.