La métastase des cellules cancéreuses est un processus caractérisé par un comportement de la cellule anormal. Les propriétés mécaniques particulières des cellules cancéreuses est l'une des caractéristiques pathologiques principales. Ces propriétés sont liées à leurs capacités à envahir les tissus avoisinants, à transmigrer et à proliférer vers de nouveaux sites. La progression du cancer est caractérisée par la perturbation et la réorganisation du cytosquelette d'actine ainsi que par des changements des propriétés mécaniques des cellules, probablement liés à la capacité dupliquée des cellules cancéreuses à migrer et à s'adapter à l'environnement.Les propriétés mécaniques sont essentielles pour la régulation des fonctions cellulaires comme la migration, l'adhésion, la prolifération, et la différentiation, et les anomalies sont associées aux pathologies, en particulier le cancer. Les propriétés mécaniques sont aussi dépendantes du micro-environnement de la cellule, et la rigidité des substrats modifie les propriétés mécaniques internes des cellules, ainsi que la structure du cytosquelette. Ainsi, comprendre les processus impliqués dans les variations des propriétés viscoélastiques est essentiel pour l'étude de la progression des tumeurs.La microscopie à force atomique (AFM) a prouvé être un outil fiable pour sonder les propriétés mécaniques statiques et dynamiques (sur de grande gamme de fréquence) de matériaux mous, comme les spécimens biologiques, à de petites échelles et grande résolution.Dans cette étude, nous proposons de nouveaux marqueurs du cancer basé sur une approche mécanobiologique. Les propriétés viscoélastiques de cellules cancéreuses de la vessie sont mesurées par des expériences d'indentation dynamiques par AFM. Cette méthode est validée en utilisant des gels de polyacrylamide et un modèle à fractions dérivées est proposé pour décrire le comportement mécanique de ces gels. Ensuite, le module de cisaillement complexe de trois lignées cellulaires à potentiel métastatique différent est mesuré à trois positions différentes de la cellule: le noyau, le périnoyau et la périphérie de la cellule. En utilisant des drogues d'inhibition de l'actine, les propriétés mécaniques sont corrélées à la microstructure de l'actine obtenue par microscopie confocale. Nous proposons un modèle simplifié pour décrire le comportement des modules élastiques G' et visqueux G''. Une relation entre l'invasivité des cellules cancéreuses et leur propriétés mécaniques est aussi mis en avant. En particulier, nous trouvons que le plateau élastique et la fréquence de transition (quand G'=G'') peuvent être utilisés comme marqueurs d'invasivité. Enfin, nous mesurons le module de cisaillement complexe de cellules cancéreuses adhérentes sur des environnements mécaniques et biologiques différents, et des propriétés intrigantes de la périphérie des cellules cancéreuses sont reportées. / Cancer cell metastasis is a multi-stage process characterized by cell malfunctional behavior. Some of the major pathological characteristics of cancer cells are their particular mechanical properties which are linked to their ability to invade surrounding tissues, transmigrate and proliferate at new sites. There are evidences that cancer progression is characterized by disruption and reorganization of the actin cytoskeleton as well as changes in the mechanical properties. This change is probably associated with the enhanced capability of cancer cells to migrate and adapt to changing environments.The mechanical properties are essential for the regulation of cell functions like migration, adhesion, proliferation and differentiation, and abnormalities are connected with pathologies, in particular cancer metastasis. The mechanical properties are also dependent on the micro-environment of the cell, as substrate stiffness changes cell internal mechanical properties, as well as the cytoskeleton structure. Thus, the understanding of the mechanics involved in the variation of the viscoelastic properties is crucial for the study of tumor progression.Atomic force microscopy (AFM) has proved to be a reliable tool to probe static and frequency–dependent mechanical properties of soft materials, like biological specimens, at small scale with high resolution.In this study, we propose new markers of cancer metastasis based on a cell mechanics approach. We report on the viscoelastic properties of human bladder cancer cells measured by dynamic indentation experiments using AFM. This method is first calibrated using polyacrylamide gels and a fractional model is proposed to describe the behavior of such gels. We then investigate the complex shear modulus of three different cell lines with different metastatic potential. We probe the elastic G' and viscous G'' modulus at three different locations across the cell: nucleus, perinucleus and the cell periphery. With the use of actin inhibitory drugs, we correlate mechanical properties and the actin microstructure obtained by confocal microscopy imaging. We propose a simplified power-law model to describe the behavior of the elastic and viscous moduli. We also report a relationship between the malignancy of cancer cells and their viscoelastic properties. In particular, we find that the elastic plateau modulus and the transition frequency (frequency at which G' = G'' ) can be used as markers of invasiveness. Then, we probe the complex shear modulus of cancer cells on different mechanical and biological environments and we report intriguing properties of the periphery of cancer cells.

Disulfide bridges play a significant role in protein-folding as well as en- zyme activity and thus regulate many intra- and extracellular processes. Sulfhydryl oxidase QSOX1 forms S-S bridges de novo, modulating the activity of its substrates and thus directly or indirectly influences vital cel- lular processes. The first part of this thesis focuses on characterization of the role of QSOX1 in cancerogenesis, using breast cancer cell lines (MCF7, MDA-MB-231) and pancreatic cancer cell line (Panc-1), while the second part emphasizes the regulation of QSOX1 expression by different oxygen concentrations. To study the effect of QSOX1 on proliferation of triple-negative cancer cells MDA-MB-231, two genetically modified cell lines - QSOX1-overexpressing and QSOX1 knockout cell lines - were constructed. While increased QSOX1 protein levels do not have a significant effect, the absence of QSOX1 leads to a decreased cellular growth. Lack of QSOX1 also results in visible change in cellular morphology. QSOX1 knockout cells can be mostly characterized as more round-shaped with less noticeable or completely missing lamellipo- dia. This finding is with agreement with to-date literature suggesting that QSOX1 is important not only for cellular proliferation but also for migration and invasiveness. While authenticating the theory of...

Disulfide bridges play a significant role in protein-folding as well as en- zyme activity and thus regulate many intra- and extracellular processes. Sulfhydryl oxidase QSOX1 forms S-S bridges de novo, modulating the activity of its substrates and thus directly or indirectly influences vital cel- lular processes. The first part of this thesis focuses on characterization of the role of QSOX1 in cancerogenesis, using breast cancer cell lines (MCF7, MDA-MB-231) and pancreatic cancer cell line (Panc-1), while the second part emphasizes the regulation of QSOX1 expression by different oxygen concentrations. To study the effect of QSOX1 on proliferation of triple-negative cancer cells MDA-MB-231, two genetically modified cell lines - QSOX1-overexpressing and QSOX1 knockout cell lines - were constructed. While increased QSOX1 protein levels do not have a significant effect, the absence of QSOX1 leads to a decreased cellular growth. Lack of QSOX1 also results in visible change in cellular morphology. QSOX1 knockout cells can be mostly characterized as more round-shaped with less noticeable or completely missing lamellipo- dia. This finding is with agreement with to-date literature suggesting that QSOX1 is important not only for cellular proliferation but also for migration and invasiveness. While authenticating the theory of...