No description available.

Dans la première partie de cette thèse, nous étudierons l’impact de l’hétérogénéité tumorale sur les phénomènes d’invasion collective des cellules cancéreuses et de dissémination métastatique.L’hétérogénéité des populations cellulaires tumorales est observée dans la plupart des lésions cancéreuses solides. Cependant, son impact sur le phénomène de métastase – élément prépondérant dans l’établissement du pronostic vital du patient – demeure à ce jour mal compris. En utilisant un modèle numérique minimal de tumeur, nous avons cherché à déterminer quel était l’impact de l’hétérogénéité des propriétés mécaniques des cellules cancéreuses sur leur invasion dans les tissus sains entourant la tumeur. Nous nous sommes particulièrement intéressés aux différences de mobilité cellulaire au sein des diverses populations cellulaires composant une tumeur. Nos travaux établissent un lien de causalité entre l’hétérogénéité tumorale et la dissémination métastatique. De plus, ils permettent de reproduire un certain nombre de morphologie d’invasion cancéreuse telles que des protrusions pluricellulaires en forme de « doigts » ou d’agrégats. Nos expériences in silico démontrent que deux mécanismes complémentaires sont à l’œuvre au sein des tumeurs hétérogènes. Une faible proportion de cellules leaders, possédant une force mobile plus élevée, est capable d’initier et de diriger l’invasion cancéreuse, alors que les effets de mouvements collectifs au sein de la tumeur fournissent la coordination mécanique nécessaire à un phénomène d’invasion collectif continu. Ces résultats suggèrent que la dynamique d’invasion collective observée durant le processus de métastase est un phénomène universel. Celui-ci est propre aux populations de cellules aux propriétés mécaniques hétérogènes, et peut être décrit en se fondant sur un nombre limité d’hypothèses physiques, et ce malgré l’importante variabilité génétique et phénotypique qui caractérise les pathologies cancéreuses.Dans la seconde partie de cette thèse, nous continuerons à étudier l’impact de l’hétérogénéité des propriétés cellulaires, cette fois à l’échelle d’un organisme pluricellulaire et non pas seulement d’un tissu. Nous nous intéresserons au développement de l’amibe sociale Dictyostelium discoideum. Lorsque les amibes sont privées de nourriture, elles forment des agrégats pluricellulaires nommés slugs,dans lesquels les cellules initialement identiques se différencient et se ségrèguent en deux populations distinctes : les cellules prespores, à l’arrière, et les cellules prestalks, à l’avant. La formation de ce motif spatial est caractérisé par une homéostasie des proportions des types cellulaires, qui demeurent quasi constants malgré les variations importantes du nombre de cellules au sein des agrégats. Si différents modèles ont été proposés pour expliquer l’origine de ce phénomène, il demeurait nécessaire de mettre en place des expériences quantitatives afin de confirmer ou d’infirmer ces modèles. Dans ce but, nous avons développé et caractérisé une nouvelle souche cellulaire de Dictyostelium, AX2-PYR, utilisant des sondes fluorescentes génétiquement encodées permettant de distinguer les différents types cellulaires au sein des slugs. Nos résultats démontrent l’invariance du motif prespore/prestalk avec la taille des slugs sur quatre ordres de grandeur, et mettent en évidence l’existence d’un mécanisme actif de régulation des proportions reposant sur les communications intercellulaires. / In the first part of this thesis, we study the impact of tumour heterogeneity on cancer collective invasion and metastatic dissemination. Heterogeneity within tumour cell populations is commonly observed in most solid tumours, but its impact on metastasis, one of the primary determinants of the disease prognosis, remains poorly understood.Working with a simplified numerical model of tumour spheroids, weinvestigate the impact of mechanical heterogeneity of tumour cells on the onset of tumour invasion into surrounding tissues, focusing more particularly on the influence of differences in cell motility. Ourwork establishes a positive link between tumour heterogeneity and metastatic dissemination, and recapitulates a number of invasion patterns identified in vivo, such as multicellular finger-like protrusionsor tumour cell clusters. In our in silico experiments, we demonstrate that two complementary mechanisms are at play in heterogeneous tumours: a small proportion of stronger cells with a higher motile force are able to initiate and lead the escape from the tumour, while collective effects in the bulk of the tumour provide the coordination required to sustain the invasive process through multicellular streaming. This suggests that the multicellular dynamics observed during metastasis is a generic feature of mechanically heterogeneous cell populations and might rely on a limited and generic set of physical assumptions shared by most tumours in spite of the genetic and phenotypic variability amongst patients and pathologies.In the second part of our work, we continue to explore the impact of heterogeneity on population scale behaviours of multicellular systems, focusing on the development of the social amoeba Dictyosteliumdiscoideum. Under starvation Dictyostelium cells form multicellular aggregates named slugs where amoeba cells differentiate and segregate into two distinct spatial zones, the prespore (rear) and prestalk (front) cells regions. This developmental pattern is characterized by an homeostasis of cell-type proportions with respect to slug size and external perturbations. Different models have been proposed to explain theorigin and regulation of this pattern, but quantitative experiments were still needed to decipher between the proposed mechanisms. To quantitatively investigate cell differentiation and spatial patterning in live multicellular aggregates, we developed and characterized a new stable cell line, AX2-PYR, using genetically encoded fluorescent reporters of cell differentiation into prespore and prestalk cells. Our results demonstrate the scaling of the prespore/prestalk pattern over more than three orders of magnitude in slug size, and show the existence of a proportion regulation mechanism which might rely on cell-cell communications.

The traditional anticancer drugs are distributed in vivo through systemic blood circulation with a very small portion reaching the tumor site. Targeted drug delivery systems are developed in efforts to concentrate the drug molecules in the tissue of interest while reducing the drug distribution to healthy tissues to reduce the side effects. Liposomes are colloidal systems composed of amphiphilic molecules that assemble into vesicle structures in aqueous media. They are common carriers for targeted drug delivery with the advantages of low toxicity, low immunogenicity and the ability of encapsulating both lipophilic and hydrophilic drugs. Prior research indicated the advantages of triggered release in drug delivery systems. As a specific example, a series of trans-2-aminocyclohexanol based lipids (flipids) have been reported to illustrate a promising strategy to render pH-triggered drug delivery systems: pH-triggered conformational switch. Based on the foregoing, we hypothesize that incorporation of lipids with a pH-sensitive conformational switch and a long-saturated lipid tail can improve the anticancer activities of stealth liposomes. In this study, six new flipids with C-16 saturated hydrocarbon tails were designed. Such lipids were synthesized with high yields by introducing a catalyst (Copper (II) tetrafluoroborate) at a key step of the synthetic scheme. pH-sensitive liposomes (fliposomes) composed of flipids were prepared and loaded with the anticancer drug doxorubicin with high encapsulation efficiency. The physicochemical properties of doxorubicin-loaded fliposomes were characterized and their pH-dependent leakage were investigated. The results showed that among all groups fliposomes containing the C-16 trans-2-morpholylcyclohexanol-based flipid (Mor-C16) exhibited the largest increase of release as the pH dropped form pH 7.4 to 6.0, indicating its good potential of serving as a component in pH-triggered drug delivery systems. Three-dimensional multicellular spheroids (3D MCS) are self-assembled microscale tissue analogs in vitro. They better mimic the native and complex tumor microenvironment than the conventional two-dimensional cell culture systems. In this dissertation study, 3D MCS of six different human cancer cells were successfully cultured and their growing conditions were optimized to obtain 3D MCS of tight structure and reproducible size. The constructed 3D MCS carried heterogeneously distributed live and apoptotic cells as well as acidic inside pH based on confocal microscopic imaging studies. The penetration of doxorubicin-loaded Mor-C16 fliposomes into 3D MCS was imaged by confocal microscopy in comparison to doxorubicin-loaded non pH-sensitive liposomes and free doxorubicin. The anticancer activities of doxorubicin-loaded Mor-C16 fliposomes against 3D MCS of three different cell lines was also evaluated by cell viability. Both the fliposome and the non pH-sensitive liposome formulations more efficiently penetrated into two of the three types of 3D MCS compared to free doxorubicin after 4h drug exposure. However, doxorubicin-loaded Mor-C16 fliposome imposed higher cytotoxicity to all three types of 3D MCS compared to doxorubicin-loaded non pH-sensitive liposome over 72 h drug exposure. Taken together, we propose that fliposomes achieved superior activity against 3D MCS by efficient penetration into 3D MCS, followed by enhanced release of the anticancer drug doxorubicin.

Matrix metalloproteinases (MMPs) are a family of zinc endopeptidases capable of digesting the extracellular matrix (ECM), which is essential for tissue structure and transmitting messages between cells. MMPs play an important role in cancer, controlling cell migration, proliferation, apoptosis, regulation of tumour expansion, angiogenesis and invasion. Previous research has indicated high expression of MT1-MMP in breast cancers suggesting a potential role in tumour progression. Our results confirm that 3D multicellular tumour spheroids (MCTS) using phenotype-specific breast cancer cell lines are a valuable experimental model of the tumour microenvironment. Optimisation of MCTS culture growth conditions using different breast cancer cell lines (MCF-7, T47D, MDA-MB-468 and MDA-MB-231) was performed. Unexpected detection of MT1-MMP in MCF-7 MCTS warranted further investigation. MT1-MMP expression in different micro-environmental conditions, including hypoxia and nutrient deprivation (serum-free induced autophagy) were measured in MCF-7 monolayer cultures and MCTS models using immunofluorescence (IF), immunohistochemistry (IHC) and western blot (WB). MT1-MMP expression was rapidly and irreversibly up-regulated in MCF-7 breast cancer cells under conditions of stress (hypoxia and autophagy) compared to normal conditions suggesting an important role of the culture environment on cells behaviour and protein expression. We employed isobaric tags for relative and absolute quantitation (iTRAQ) technology to correlate MT1-MMP increase with proteomic profiles in MCF-7 breast cancer cell grown under hypoxic, serum-free and 3D MCTS conditions. More than 3500 proteins were identified, which were clustered into groups based on response to unique or shared microenvironment changes. Hypoxic monolayer and spheroid cells exhibited changes in anaerobic metabolism and lipid synthesis, respectively, whereas autophagy resulted in up-regulation of cellular component disassembly. The result indicated multiple drivers of MT1-MMP expression in MCF-7 cells. / Al-Mstansiriya University, Iraq

No description available.

La thérapie photodynamique (PDT) est un traitement alternatif à la chirurgie en oncologie utilisant un photosensibilisateur (PS), la lumière visible et l’oxygène moléculaire. La méta-tétra(hydroxyphényl)chlorine (mTHPC) est l’un des PS de deuxième génération les plus utilisés en clinique en raison de son absorption dans le rouge lointain et d’un rendement quantique en 1O2 élevé. De par sa nature hydrophobe, la mTHPC est partiellement agrégée dans la circulation sanguine diminuant sa biodistribution. Dans le but d’améliorer la sélectivité tumorale de la mTHPC, différentes stratégies de vectorisation ont été développées. La formulation liposomale de mTHPC non PEGylée (Foslip®) améliore la biodistribution ainsi que les propriétés pharmacocinétiques de la mTHPC. Cependant, une rapide destruction des liposomes en circulation ainsi qu’une rapide libération de la mTHPC sont des inconvénients majeurs. Une alternative possible est l’utilisation de vésicules extracellulaires (VE). Dérivées des cellules, les VE possèdent une stabilité naturelle dans la circulation sanguine et une capacité à transporter et délivrer leur contenu de manière spécifique aux cellules cancéreuses. Cette vectorisation est intéressante en PDT en raison d’une importante capacité d’encapsulation des porphyrines. Le but de cette étude était d’évaluer l’intérêt des VE en tant que nanovecteur de la mTHPC dans divers modèles précliniques comparé au Foslip®. Contrairement au Foslip®, l’intégrité membranaire des VE est conservée en présence de 20% de plasma. In vitro, les mTHPC-VE ont montré une internalisation cellulaire par un mécanisme actif d’endocytose. Dans un modèle cellulaire en 3D de sphéroïdes multicellulaires, les mTHPC-VE ont permis d’accroitre l’accumulation cellulaire, la diffusion au sein de ce modèle ainsi que l’efficacité PDT. In vivo, les mTHPC-VE apparaissent plus efficace au niveau PDT avec un retard de croissance tumorale significativement augmenté. En conclusion, l’intégration de la mTHPC au sein des VE améliore l’efficacité PDT dans les différents modèles d’étude. Le suivi des mTHPC-VE à l’aide d’un traceur radioactif chez la souris ainsi que l’étude du ciblage de la vascularisation tumorale seront étudiés dans la suite du travail / Photodynamic therapy (PDT) is an alternative treatment to surgery in oncology using photosensitizer (PS), light and oxygen. Meta-tetra(hydroxylphenyl)chlorin (mTHPC) is one of the most used PS in clinics due to its high absorption in the deep red and high 1O2 quantum yield. In order to improve the mTHPC tumor selectivity different attempts of nanovectorisation were conducted. Non-PEGylated liposomal mTHPC (Foslip®) increase biodistribution and pharmacokinetic properties. However, the rapid liposome destruction during circulation and rapid mTHPC release are obvious shortcomings. Alternatively, mTHPC vectorization could be realized by extracellular vesicles (EVs). Derived from the cell, EVs possess a natural stability in bloodstream and ability to transport and deliver cargo molecules into cancer cells. This formulation is interesting for PDT due to the ability to encapsulate porphyrins. The aim of the present study was to determine the interest of EVs as mTHPC nanocarriers in various preclinical models compared to Foslip®. In contrast to Foslip®, membrane integrity of mTHPC-EVs was conserved in 20% of plasma. In vitro, mTHPC-EVs showed cellular internalization by an active endocytosis mechanism. In a 3D model of spheroids, mTHPC-EVs have improved cellular uptake, better diffusion inside spheroid and increased PDT efficacy. In vivo, mTHPC-EVs appeared to be more potent in terms of PDT efficacy, with a tumor growth delay significantly higher. In conclusion, integration of mTHPC in EVs improves PDT efficacy in various preclinical models. The tracking of mTHPC-EVs using a radioactive tracer in xenografted rodents as well as the study of vascularization targeting will be studied in the next step of this work

Orientador: Celso de Almeida, Rodrigo Pereira Ramos / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Eletrica e de Computação / Made available in DSpace on 2018-08-08T10:36:25Z (GMT). No. of bitstreams: 1 Britto_PauloMarceloPerezRodriguesde_M.pdf: 4780408 bytes, checksum: c3b152e041128b5d94429d8b87c0068c (MD5) Previous issue date: 2006 / Resumo: O desempenho de sistemas de comunicações sem fio que utilizam técnicas de espalhamento espectral e múltiplo acesso por divisão de código (CDMA) é limitado pela interferência. Nesta dissertação, analisamos o desempenho de um algoritmo de seleção de seqüências de espalhamento de comprimento fixo, que busca a minimização dos efeitos de interferência em sistemas CDMA operando em canais com desvanecimento seletivo em freqüência e possuindo células adjacentes interferentes. Analisamos o desempenho deste sistema no qual o espalhamento espectral é feito usando duas seqüências: seqüências do usuário e seqüências identificadoras de células. Dentre as seqüências analisadas, podemos citar as Walsh, a Gold, as de comprimento máximo e também um tipo de seqüência de espalhamento baseado nas seqüências de comprimento máximo / Abstract: The performance of wireless communication systems using spread spectrum techniques and code division multiple access (CDMA) is interference-limited. In this dissertation, we evaluate the performance of a selection algorithm for fixed-length spreading sequences, aimed on minimizing the interference effects in CDMA systems operating in frequency selective fading channels and having adjacent interfering cells. We check the performance of this system where the spread spectrum operation is performed using two sequences: user sequences and cell identification sequences. Among the sequences considered, we use Walsh, Gold, maximum length and a type of spreading sequence based on the maximum length class / Mestrado / Telecomunicações e Telemática / Mestre em Engenharia Elétrica

Les gliomes sont des tumeurs qui seforment par prolifération anormale de cellules dansle tissu cérébral. La dangerosité de ces tumeursréside dans le fait que la plupart des gliomes sontinvasifs : les cellules tumorales migrent dans le tissusain autour de la tumeur. Ces cellules tumoralesisolées provoquent des récidives quasi systématiquesaprès traitement (chirurgie, chimiothérapie,radiothérapie), rendant ces tumeurs incurablesactuellement et conduisant au décès du patient. Il estimportant d'associer des études fondamentales pourmieux comprendre leur évolution dès l'origine et desétudes plus appliquées en développant de nouveauxsubstrats pour reproduire in vitro leur évolution. Lescellules progénitrices des oligodendrocytes (OPC)représentent la plus grande population de cellules enprolifération et la plus largement distribuée dans lecerveau adulte, ce qui en fait un suspect idéal del’origine des gliomes. A partir de donnéesexpérimentales de la littérature sur la dynamique invivo de ces cellules, un modèle mathématiquereproduisant cette dynamique dans un tissu sain a étédéveloppé.Ce modèle montre également que les OPC pourraientêtre à l’origine de toutes les formes de gliomerencontrées aussi bien de bas grade que de hautgrade. Par ailleurs, l’approche expérimentale utiliséevisait à développer un substrat de culture cellulaireadapté à l’étude des gliomes in vitro. Ainsi, unhydrogel biocompatible, minimaliste et contrôlable aété élaboré. Celui-ci mime l’élasticité de la matriceextracellulaire (MEC) cérébrale avec une rigidité del’ordre de 200 Pa et l’effet adhésif des molécules dela MEC impliqué dans l’adhésion et la proliférationdes cellules tumorales. Grâce à ses propriétés,l’hydrogel favorise la survie de près de 90% desmodèles cellulaires de gliome utilisés dans notreétude et supporte la croissance en trois dimensionsd’agrégats multicellulaires semblables à lamorphologie de micro-tumeurs in vivo. Le modèled’hydrogel est donc validé pour favoriser la viabilitéet la prolifération cellulaires. Les perspectives detravail futures porteront sur l'optimisation de sacomposition pour mimer de manière encore plusréaliste la croissance tumorale in vivo. / Gliomas are brain tumors arising fromanomalous cell proliferation into the brain tissue.The hazard of these tumors resides in their invasiveability : tumor cells migrate into the healthy tissuesurrounding the tumor. These isolated cells causequasi systematic recurrences after treatment(surgery, chemotherapy, radiotherapy) making thesetumors currently incurable and leading to patientdeath. Hence, it is important to associatefundamental studies for better understanding of theirevolution from their origin with more appliedstudies developing new substrates for reproducingtheir evolution in vitro. Oligodendrocyte progenitorcells (OPC) are the most widely spread proliferatingpopulation in the adult brain, which makes them themain suspect of causing gliomas origin. Fromexperimental data in the literature about in vivodynamic of OPC, a mathematical model that depictsthis dynamic into a healthy tissue has beendeveloped.This model also shows that OPC could be at theorigin of all glioma forms from low to high grade.Furthermore, the experimental approach used aimedat designing a cell culture substrate adapted toglioma studies in vitro. Thus, a biocompatible,minimalistic and controllable hydrogel has beenperformed. It mimics brain extracellular matrix(ECM) elasticity around 200 Pa and the adhesiveeffect of ECM molecules involved in tumor celladhesion and proliferation. Due to these properties,the hydrogel contributes to around 90% of gliomacell models survival used in our study and promotesmulticellular aggregates growth in three dimensionsthat look like in vivo microtumors morphology. Thishydrogel model is thus validated for cell viabilityand proliferation. Future works will be devoted tothe optimization of its composition for bettermimicking of tumor growth in vivo in a morerealistic manner.

Cell contractility is mainly imagined as a force dipole-like interaction based on actin stress fibers that pull on cellular adhesion sites. Here, we present a different type of contractility based on isotropic contractions within the actomyosin cortex. Measuring mechanosensitive cortical contractility of suspended cells among various cell lines allowed us to exclude effects caused by stress fibers. We found that epithelial cells display a higher cortical tension than mesenchymal cells, directly contrasting to stress fiber-mediated contractility. These two types of contractility can even be used to distinguish epithelial from mesenchymal cells. These findings from a single cell level correlate to the rearrangement effects of actomyosin cortices within cells assembled in multicellular aggregates. Epithelial cells form a collective contractile actin cortex surrounding multicellular aggregates and further generate a high surface tension reminiscent of tissue boundaries. Hence, we suggest this intercellular structure as to be crucial for epithelial tissue integrity. In contrast, mesenchymal cells do not form collective actomyosin cortices reducing multicellular cohesion and enabling cell escape from the aggregates.

No description available.