Angiogenesis and vascular permeability occur in physiological and pathological conditions. Angiogenesis denotes the process of blood vessel formation from preexisting quiescent vessels. Angiogenesis is initiated by proangiogenic factors, inducing endothelial cell sprouting, migration and anastomosis, followed by regression of the new vessels or maturation into a quiescent status. Vascular permeability is the process where blood vessels exchange nutrients, solutes and inflammatory cells with the surrounding tissue. Small molecules freely cross the endothelial wall, however macromolecules and cells leak out from the vasculature only after stimulation by certain factors, including VEGF. Angiogenesis and vascular permeability are tightly regulated physiological processes, but uncontrolled angiogenesis and excessive leakage lead to pathological conditions and the progression of several diseases. VEGF and its receptor VEGFR2 are critical players in angiogenesis and in vascular permeability. The binding of the ligand to the receptor is not the only event involved in the activation and regulation of the signaling cascade. Coreceptors, kinases, phosphatases, and other proteins involved in the trafficking of the complex modulate the signal amplitude and duration. VEGF/VEGFR2 complex combined with the coreceptor NRP1 has a strong pro-angiogenic action and a critical role in angiogenesis. Both VEGFR2 and NRP1 bind VEGF and can present VEGF in cis, when both VEGFR2 and NRP1 are expressed on the same endothelial cell or in trans, when NRP1 is expressed on an adjacent endothelial cell or another type of cell. Y949 and Y1212 are two of the main phosphorylation sites of VEGFR2 induced by VEGFA. The binding of phosphorylated Y949 to the SH2 domain of TSAd regulates vascular permeability leading to Src activation and adherens junction opening in vitro. Phospho-Y1212 is implicated in actin stress fiber remodeling via the adapter Nck, affecting the actin cytoskeleton and endothelial cell migration in vitro. Paladin is a vascular-enriched phosphatase-domain containing protein without reported phosphatase activity and is a negative regulator of insulin receptor and Toll-like receptor 9 signaling. In this thesis work, I have investigated the spatial dynamics of NRP1/VEGFR2 complex formation (in cis and in trans) for coordinating VEGF-mediated angiogenesis in physiological and in pathological conditions (Paper I). I have studied, in vivo, the role of VEGFR2 Y949 in vascular permeability and metastatic spread (Paper II) and the role of VEGFR2 Y1212 in angiogenic remodeling and vessel stability (Paper III). Furthermore, I have examined paladin’s role in regulating VEGF/VEGFR2 signaling and VE-cadherin junction stability, in angiogenic sprouting and vascular permeability (Paper IV). In conclusion, VEGF/VEGFR2 signaling is regulated by a multifactor system and each individual regulatory mechanism leads to a specific outcome in angiogenesis, vascular permeability and vessel stability.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

The novel protein Carom is a homolog of the Drosophila protein, Nervous Wreck (Nwk). Carom was cloned as a homocysteine response protein in primary endothelial cells (EC). In order to discern the functionality of the protein in higher order mammals and potential role in homocysteine-inhibited angiogenesis, we performed basic characterization studies on Carom. Theoretical modeling of Carom matched the solved structure of Nwk. Using a lab-generated antibody against Carom’s F-BAR domain, it is evident that Carom is localized to the mitochondria and speckling in the nucleus of primary ECs. In order to perform biochemical and structural studies in primary ECs, Carom was cloned from an adenoviral shuttle vector to an adeno-associated virus (AAV) transfer vector. We created a multi-cistronic open reading frame with an N-terminal Flag and a cleavable C-terminal green fluorescent protein (mClover3). Primary ECs are difficult to transfect, so we optimized an AAV packaging system in order to get high titers and high purity AAV that can transduce our primary ECs. Carom is composed of several functional domains with the capability of binding to cell membranes and act as a scaffolding for attaching adaptor proteins. To isolate which domains are important to the partner binding and cellular localization, we serially truncated the domains from Carom starting from both the C-terminus and N-terminus. We demonstrated that the C-terminal region features some post-translational modifications creating the second band in western blots with lower mobility. Also, the F-BAR domain is responsible for translocalization of Carom from the cytoplasm to the cell membrane and nucleus. A novel mechanism is proposed for why Carom is upregulated in response to homocysteine (Hcy), an independent risk factor for cardiovascular disease. It is previously known that Hcy inhibits angiogenesis. Our data mining studies identified a potentially important receptor for angiogenesis in ECs, VEGFR2, being endocytosed and ultimately degraded. Through biotinylation assays, we determined that Carom does help enhance the endocytosis of VEGFR2 potentially leading to degradation via the lysosome. In summary, Carom is endogenously localized to the mitochondria in primary ECs, the C-terminus is post-translationally modified, the bipartite nuclear localization signal containing F-BAR domain localizes to the cell membrane and nucleus, and Carom enhances the endocytosis of VEGFR2. / Biomedical Sciences

Yes / Most cancer patients receive chemotherapy at some stage of their treatment which makes improving the efficacy of cytotoxic drugs an ongoing and important goal. Despite large numbers of potent anti-cancer agents being developed, a major obstacle to clinical translation remains the inability to deliver therapeutic doses to a tumor without causing intolerable side effects. To address this problem, there has been intense interest in nanoformulations and targeted delivery to improve cancer outcomes. The aim of this work was to demonstrate how vascular endothelial growth factor receptor 2 (VEGFR2)-targeted, ultrasound-triggered delivery with therapeutic microbubbles (thMBs) could improve the therapeutic range of cytotoxic drugs. Methods: Using a microfluidic microbubble production platform, we generated thMBs comprising VEGFR2-targeted microbubbles with attached liposomal payloads for localised ultrasound-triggered delivery of irinotecan and SN38 in mouse models of colorectal cancer. Intravenous injection into tumor-bearing mice was used to examine targeting efficiency and tumor pharmacodynamics. High-frequency ultrasound and bioluminescent imaging were used to visualise microbubbles in real-time. Tandem mass spectrometry (LC-MS/MS) was used to quantitate intratumoral drug delivery and tissue biodistribution. Finally, 89Zr PET radiotracing was used to compare biodistribution and tumor accumulation of ultrasound-triggered SN38 thMBs with VEGFR2 targeted SN38 liposomes alone. Results: ThMBs specifically bound VEGFR2 in vitro and significantly improved tumor responses to low dose irinotecan and SN38 in human colorectal cancer xenografts. An ultrasound trigger was essential to achieve the selective effects of thMBs as without it, thMBs failed to extend intratumoral drug delivery or demonstrate enhanced tumor responses. Sensitive LC-MS/MS quantification of drugs and their metabolites demonstrated that thMBs extended drug exposure in tumors but limited exposure in healthy tissues, not exposed to ultrasound, by persistent encapsulation of drug prior to elimination. 89Zr PET radiotracing showed that the percentage injected dose in tumors achieved with thMBs was twice that of VEGFR2-targeted SN38 liposomes alone. Conclusions: thMBs provide a generic platform for the targeted, ultrasound-triggered delivery of cytotoxic drugs by enhancing tumor responses to low dose drug delivery via combined effects on circulation, tumor drug accumulation and exposure and altered metabolism in normal tissues. / EPSRC funding (EP/I000623/1, EP/K023845/1 and EP/P023266/1) and the MRC for a Confidence in Concept award and MR/L01629X. L.E. McVeigh was funded by an EPSRC PhD Studentship (EP/L504993/1).

Le système nerveux et le système vasculaire montrent de grandes similitudes notamment au niveau anatomique. Il est maintenant communément admis que des membres des quatre grandes familles de molécules de guidage axonal Sémaphorines, Ephrines, Nétrines et Slits et leurs récepteurs sont également impliqué dans la mise en place du réseau vasculaire, mais la situation inverse n'était pas aussi claire lorsque j'ai débuté ma thèse. Cette thèse s'intéresse au rôle chez la souris de deux molécules de mise en place du système vasculaire VEGFR2 et Synectine dans le contexte du guidage axonal. Nous avons ainsi montré que ces deux molécules sont importantes pour le guidage de différentes populations d'axones par la molécule de guidage axonal Sémaphorine 3E (Séma3E). Dans une première étude, nous avons montré que VEGFR2 est important pour la mise en place du faisceau subiculo-mamillaire in vivo indépendamment de son ligand vasculaire habituel VEGF. En effet, dans ces neurones VEGFR2 agit au sein d'un complexe récepteur à Séma3E, composé de PlexinD1, Neuropilin1, et VEGFR2. Ainsi, la liaison de Séma3E au complexe récepteur entraine l'activation de VEGFR2 qui transduit alors une signalisation promotrice de croissance axonale en activant la voie PI3K/Akt. Dans une seconde étude, nous avons montré que Synectine est important in vivo pour la mise en place de la commissure antérieure, un autre faisceau axonal exprimant le récepteur à Séma3E, PlexinD1. De plus, nous avons montré in vitro que Synectine est nécessaire à la réponse inhibitrice de croissance induite par Séma3E dans les neurones du cortex latéral piriforme qui correspondent aux neurones projetant dans la commissure antérieure. En impliquant Synectine et VEGFR2 dans le guidage axonal, les résultats présentés dans cette thèse mettent donc en avant que si le système vasculaire utilise des molécules du système nerveux pour son développement, le système nerveux peut également utiliser des molécules du système vasculaire pour la mise en place de son réseau neuronal. / Important similarities exist between the vascular and the nervous systems, both at anatomical and molecular levels. There is now clear evidence that members of all four classical families of axon guidance molecules (Ephrins, Netrins, Slits, and Semaphorins) and their cognate receptors are implicated in vascular patterning. Here we present evidence for the reverse situation in wich two vascular molecules, VEGFR2 and Synectin, are implicated in axon patterning of two major axon tract in vivo, and in their response to the axon guidance molecule Semaphorin 3E in vitro.

Advances in optical imaging have provided methods for visualizing molecular expression in tumors in vivo, allowing the opportunity to study the complexity of the tumor microenvironment. The development of fluorescent contrast agents targeted to molecules expressed in cancer cells is critical for in vivo imaging of the tumors. Contrast agents emitting in the near infrared (NIR) allow for an increased depth of penetration in tissue due to decreased absorption and scattering. There is also significantly less autofluorescence from tissue in the NIR. Quantum dots are nanoscopic particles of semiconductors whose fluorescent emission wavelength is tunable by the size of the particle with desirable fluorescent qualities such as a wide range of excitation wavelengths, a narrow emission band, high quantum efficiency, high photostablility, and they can be produced to emit throughout the NIR imaging window. It has been shown that vascular endothelial growth factor receptor 2 (VEGFR2) is upregulated in many cancers, including colorectal, as it is important in tumor angiogenesis and is considered a predictor for clinical outcome and, in some instances, is used for targeted therapy with anti-angiogenic drugs. For these reasons, quantum dots bioconjugated to VEGFR2 antibodies have the potential to provide contrast between normal tissue and cancer, as well as a mechanism for evaluating the molecular changes associated with cancer in vivo. In this dissertation, we present on the design of two contrast agents using quantum dots targeted to VEGFR2 for use in the molecular imaging of colon cancer, both ex vivo and in vivo. First, as a preliminary ex vivo investigation into their efficacy, Qdot655® (655nm emission) were bioconjugated to anti-VEGFR2 antibodies through streptavidin/biotin linking. The resulting QD655-VEGFR2 contrast agent was used to label colon adenoma in vivo and imaged ex vivo with significant increase in contrast between diseased and undiseased tissue, allowing for fluorescence based visualization of the VEGFR2 expressing diseased areas of the colon with high sensitivity and specificity. Then, QD655-VEGFR2 was used in a longitudinal in vivo study to investigate ability to correlate fluorescence signal to tumor development over time using optical coherence tomography and laser induced fluorescence spectroscopy (OCT/LIF) dual-modality imaging. The contrast agent was able to target VGEFR2 expressing diseased areas of colon; however, challenges in fully flushing the unbound contrast agent from the colon before imaging arise when moving from ex vivo imaging to in vivo image. Lastly, lead sulfide (PbS) quantum dots were made by colloidal synthesis to emit at a 940 nm (QD940) and conjugated to anti-VEGFR2 primary antibodies through streptavidin/biotin linking. The resulting QD940-VEGFR2 contrast agent was then used to label cells in vitro. The QD940-VEGFR2 molecules were able to positively label VEGFR2 expressing cells and did not label VEGFR2 negative cells. Very low photoluminescence and large amounts of aggregation after conjugation of the quantum dot to streptavidin was detected. Improvements to the quantum dot stability through synthesis, capping and conjugation techniques must be made for this contrast agent to be effective as a contrast agent for cancer imaging.

v anglickom jazyku Charles University in Prague Faculty of Pharmacy in Hradec Králové Department of Biophysics and Physical Chemistry Student: František Lach Supervisor: Mgr. Pavel Bárta, PhD Consultant: Mgr. Lucie Hyršová Title of diploma thesis: In vitro saturation study of 99m Tc-HYNIC-ramucirumab on PC-3 cell line The number of malignant tumours in the population has increased in recent years. Due to the frequent serious sides effects of chemotherapeutic drugs on the whole organism, targeted antitumor therapy is at the forefront. Due to its specific effect on the regulatory and signal pathways of protein structures, monoclonal antibodies are used for the target anti-tumour therapy. The basic properties of the growing tumour include vasculogenesis (the ability to build new blood vessels from the endothelial precursors) and angiogenesis (the process of self-inducing formation of blood vessels). Endothelial tumour progenitors include vascular endothelial growth factor (VEGF). VEGF activates its biological activity by binding to its transmembrane tyrosine-kinase receptors VEGFR. Indeed, the inhibition of the vascular endothelial factor receptors is the target of some monoclonal antibodies. Ramucirumab is a monoclonal antibody that selectively inhibits VEGF receptor type 2 (VEGFR-2) and thereby...

Yes / Advanced drug delivery systems, such as ultrasound-mediated drug delivery, show great promise for increasing the therapeutic index. Improvements in delivery by altering the ultrasound parameters have been studied heavily in vitro but relatively little in vivo. Here, the same therapeutic microbubble and tumour type are used to determine whether altering ultrasound parameters can improve drug delivery. Liposomes were loaded with SN38 and attached via avidin: biotin linkages to microbubbles. The whole structure was targeted to the tumour vasculature by the addition of anti-vascular endothelial growth factor receptor 2 antibodies. Tumour drug delivery and metabolism were quantified in SW480 xenografts after application of an ultrasound trigger to the tumour region. Increasing the trigger duration from 5 s to 2 min or increasing the number of 5 s triggers did not improve drug delivery, nor did changing to a chirp trigger designed to stimulate a greater proportion of the microbubble population, although this did show that the short tone trigger resulted in greater release of free SN38. Examination of ultrasound triggers in vivo to improve drug delivery is justified as there are multiple mechanisms at play that may not allow direct translation from in vitro findings. In this setting, a short tone burst gives the best ultrasound parameters for tumoural drug delivery. / This research was funded by the EPSRC (EP/I000623/1, EP/L504993/1 and EP/P023266/1). S.D.E. is supported by the National Institute for Health Research infrastructure at Leeds. J.R.M. is supported by an EPSRC UKRI Innovation Fellowship (EP/S001069/1).

Les protéines kinases représentent le groupe d'enzymes qui servent d'intermédiaire pour la phosphorylation de protéines - le transfert d'un groupe phosphate de l'adénosine triphosphate(ATP) sur des chaînes latérales correspondantes de tyrosine, de serine ou de thréonine des acides aminées. La phosphorylation de protéines est un des outils les plus importants pour la régulation de l'activité cellulaire. La « signalisation » cellulaire par le récepteur de tyrosine kinase VEGFR2 (KDR) appartient aux réactions biochimiques clés influençant la croissance de tumeurs. L'inhibition thérapeutique de cette réaction à l'aide des composés de faible poids moléculaire spécifiques est devenue une stratégie utile dans le cadre des thérapies anticancéreuses. Ce travail a amené à la découverte de 16 substances biologiquement actives sur la base N,5-diaryloxazol-2-amine (IC50, VEGFR2 TK). D'excellents résultats ont été atteints notamment dans le cas des substances 189, 191, 211, 214, 220, 221, 223 et 4 qui montrent une activité inhibitrice inférieure à 500 nM. / Protein kinases represent a group of enzymes responsible for phosphorylation - transfer of aphosphate group from adenosine triphosphate (ATP) to tyrosine or serine/threonine residues. Protein phosphorylation is one of the most important tools regulating a cell activity. A cell "signalization" through an endothelial receptor tyrosine kinase VEGFR2 TK (KDR) is the important pathway influencing growth of a tumor. Small-molecule inhibitors of VEGFR2 TK (VEGFR2 TKls) have become an important tool for the treatment of various types of cancer. This dissertation thesis resulted in a discovery of 16 biologically active N,5-diaryloxazol-2-amines (IC50, VEGFR2 TK). Very good results were achieved especially with compounds 189, 191, 211, 214, 220, 221, 223 and 4 exhibiting the activity under 500 nM.