La polarité apico-basale des cellules épithéliales est maintenue au niveau cellulaire par l’implication de plusieurs complexes protéiques, PAR, SCRIBBLE et CRUMBS, et par l’intégrité des jonctions serrées et adhérentes. La polarité apico-basale est essentielle au bon déroulement des processus de division, d’apoptose et de migration cellulaire, et de nombreuses études montrent que les perturbations de la polarité interviennent dans la progression tumorale. Notre travail a porté sur la recherche d’anomalies biologiques modifiant la polarité apico basale et l’adhésion cellulaire dans les carcinomes mammaires. Nous avons choisi d’étudier deux types spéciaux de carcinomes mammaires infiltrant, dont le phénotype suggère l’existence d’altérations spécifiques de ces processus biologiques: le type lobulaire (ILC) et le type micropapillaire (IMPC). Ces études ont été menées par des analyses combinées phénotypiques, transcriptomiques et génomiques comparatives, par rapport à un groupe de carcinomes mammaires sans autre spécificité (IC-NST).Les carcinomes lobulaires sont caractérisés par les altérations du complexe E cadhérine/ caténine et leur capacité de dissémination métastatique. Nous avons montré qu’ils présentent également une sous-expression de la protéine du complexe PAR, PAR-3, associée à des altérations des gènes impliqués dans l’adhésion cellulaire (ADAM12, LOXL2), l’interaction cellule-matrice extracellulaire (MMP11, COL11A1, etc…) et l’invasion (ACTR2, PAK1). Des défauts quantitatifs des constituants de la matrice extracellulaire ont également été mis en évidence. Nous avons, ainsi, pu établir une signature transcriptomique spécifique de cette entité tumorale, en accord avec les caractéristiques morphologiques observées. Les carcinomes micropapillaires présentent une polarité anormale caractérisée par des marqueurs apicaux positionnés vers la matrice extracellulaire ou absents, la perte de l’orientation de la protéine golgienne GM130, des anomalies des jonctions serrées (occludine) et des protéines du complexe PAR (CDC42 et aPKC). Au niveau génomique, nous avons mis en évidence des mutations somatiques de gènes impliqués dans la régulation de la polarité (DNAH9, FOXO3) et de la ciliogenèse (BBS9, BBS12, SEC63), l’organisation du cytosquelette (HSP90B1, UBR4, ZFYVE26) et la motilité (FMN2). Au niveau transcriptomique, une nette perturbation des gènes impliqués dans l’adhésion cellule cellule, cellule-matrice extracellulaire et l’angiogenèse est observée. Les IMPC présentent également une surexpression spécifique d’une protéine du complexe CRUMBS, LIN7A. Nous avons établi un modèle in vitro et avons montré que LIN7A est un puissant perturbateur de la polarité apico basale. Sa surexpression dans la lignée MCF10A cultivée en 3D induit la formation d’acini multilobés, à forte capacité proliférative et sans lumière centrale. Cette absence de lumière centrale est due à une inhibition de l’apoptose. Les cellules MCF10A-LIN7A présentent également une capacité accrue de croissance en suspension, témoignant d’une résistance à l’anoïkis. Cette résistance est due, entre autre, à une diminution de la phosphorylation de la protéine p38. Cette description approfondie des altérations biologiques de types spéciaux de carcinomes mammaires doit permettre à moyen terme de proposer une prise en charge plus spécifique des patientes, grâce à l’identification de nouvelles possibilités thérapeutiques ou à une stratégie de désescalade thérapeutique. / Apicobasal polarity is maintained by the combined action of several protein complexes – PAR, SCRIBBLE and CRUMBS – together with the structural organisation of adherent and tight junctions. Apicobasal polarity is important for the regulation of cell division, apoptosis and cell migration, and several studies show that disruption of cell polarity is involved in tumour progression. Our work focused on the biological mechanisms responsible for the altered apicobasal polarity and cell adhesion observed in breast cancers. To do so, we studied two types of breast carcinomas – invasive lobular carcinoma (ILC) and invasive micropapillary carcinoma (IMPC) – whose morphology suggests specific alterations of these cell processes. Our approach combined genomic, transcriptomic and phenotypical comparative analyses, using a group of invasive carcinomas not special type (IC-NST) as control.Lobular carcinomas are generally characterized by alterations of the E cadherin/ catenin complex and their ability to disseminate. We have shown that they also present a downregulation of PAR-3, a protein of the PAR complex, associated with deregulation of genes involved in cell adhesion (ADAM12, LOXL2), cell-extracellular matrix interactions (MMP11, COL11A1, etc…) and invasion (ACTR2, PAK1). Quantitative defects in components of the extracellular matrix were also observed. We have thus been able to establish a transcriptomic signature for this tumour entity, in agreement with the phenotypical observations.Micropapillary carcinomas show an abnormal polarity characterized by the absence of apical markers or their localization at the inverted apical pole, the loss of Golgi protein GM130 correct orientation and abnormal expression or localization of occludin (tight junctions), CDC42 and aPKC(PAR complex proteins). At the genomic level, we have identified somatic mutations in genes involved in polarity (DNAH9, FOXO3) and ciliogenesis regulation (BBS9, BBS12, SEC63), cytoskeleton organisation (HSP90B1, UBR4, ZFYVE26) and motility (FMN2). At the transcriptomic level, we observed deregulation of genes involved in cell-cell, cell-extracellular matrix adhesion and angiogenesis. IMPC also demonstrate the specific overexpression of a protein of the CRUMBS complex, LIN7A. We established an in vitro model and showed that LIN7A is an efficiently modifier of MCF10A’s polarity. Its overexpression in MCF10A cells cultured in 3-D conditions induces the formation of proliferating multi-lobar acini with no central lumen. This absence of a central lumen is due to an inhibition of apoptosis. MCF10A-LIN7A cells also show an increased ability to grow in suspension, indicating resistance to anoikis. This resistance seems to be linked to a decrease of p38protein’s phosphorylation.This detailed description of biological alterations in special types of breast carcinomas will contribute to more specific treatments provided to the patients, through the identification of new therapeutic targets or therapeutic strategies.

An ionic polymer actuator consists of a thin Nafion-117 sheet plated with gold or platinum on both sides. An ionic polymer actuator undergoes large deformation in the presence of low applied voltage across its thickness and exhibits low impedance. They can also be used as large displacement sensors by bending them to induce stresses and generate a voltage response. They operate best in a humid environment. Ionic polymer actuators have been used for various practical applications such as bio-mimetic robotic propulsion, flexible low mass robotic arms, propellors for swimming robotic structures, linear and platform type robotic actuators and active catheter systems. One of the disadvantages of ionic polymer actuators is that their settling time to a unit step voltage is on the order of 5-20 seconds in a cantilever configuration. The slow time constant of an ionic polymer limits the actuation bandwidth. The characteristics of ionic polymer actuators, low force and large displacement (as compared to other actuator technologies such as PZT or PVDF), cannot be used in applications requiring a faster response time for a given actuation signal. Due to this limitation, many applications will not be able to make use of the large displacement effectively because of the limited bandwidth of the actuator. Another disadvantage of using an ionic polymer actuator is that the stiffness of the actuator is a function of the hydration of the polymer. Difficulties in controlling the hydration, which changes with respect to time, results in inconsistencies in the mechanical response exhibited by the polymers during continual usage. Several physical models of ionic polymer actuators have been proposed. The physical phenomenon responsible for the bending is not completely understood and no clear set of principles have been able to explain the motion of the polymers completely. Physical phenomena like ionic motion, back diffusion of water and electrostatic force have been used to explain these models. This research demonstrates the use of feedback control to overcome the limitation of slow settling time. First, an empirical model of the ionic polymers developed by Kanno was modified by studying the step response of these actuators. The empirical model is used to design a feedback compensator by state space modeling techniques. Since the ionic polymer actuator has a slow settling time in the open-loop, the design objectives are to minimize the settling time and constrain the control voltage to be less than a prescribed value. The controller is designed using Linear Quadratic Regulator (LQR) techniques which reduced the number of design parameters to one variable. Simulations are performed which show settling times of 0.03 seconds for closed-loop feedback control are possible as compared to the open-loop settling time of 16-18 seconds. The maximum control voltage varied from 1.2 Volts to 3.5 Volts depending on the LQR design parameter. The controller is implemented and results obtained are consistent with the simulations. Closed-loop settling time is observed to be 4-8 seconds and the ratio of the peak response to the steady-state response is reduced by an order of magnitude. Discrepancies between the experiment and the simulations are attributed to the inconsistencies in the resonant frequency of the actuator. Experiments demonstrate that changes in the surface hydration of the polymer result in 20\% variations in the actuator resonance. Variations in the actuator resonance require a more conservative compensator design, thus limiting the performance of the feedback control system. / Master of Science