Il est généralement admis que le cancer du sein représente un ensemble de plusieurs maladies, définies comme des sous-types ayant des caractéristiques moléculaires et cliniques qui leurs sont propres. Une meilleure compréhension des mécanismes qui sous-tendent l'hétérogénéité du cancer du sein est essentielle au développement de thérapies mieux ajustées. Le concept de cellules souches cancéreuses (CSC) pourrait être un des clés de cette compréhension. A ce jour, un certain nombre de marqueurs ont été proposés pour isoler et caractériser les cellules souches dans le cancer du sein, mais aucun ne semble totalement satisfaisant.Le but de mon travail était de déterminer un marqueur ou une combinaison de marqueurs avec lesquels les fractions enrichies en CSC pourraient être isolées de manière reproductible dans le cancer du sein de sous-types basal (BLBC). En effet, les tumeurs basales représentent 15% de toutes les tumeurs mammaires, mais constituent le sous-type le plus agressif. À cet effet, j'ai analysé un certain nombre de marqueurs par analyse FACS et tri cellulaire et utilisé la capacité de formation de mammosphères (MS) comme critère de validation pour la présence de CSC. Les lignées cellulaires utilisées comme modèles étaient les SUM 159, MDA-MB-231, MDA-MB-436, HCC1143, MDA-MB-468, Hs578T et BT-549 correspondant aux modèles basal-A et B. J'ai également testé trois lignées luminales les MCF7, T47D et BT474.De tous les marqueurs testés, seules, la combinaison des protéines de surface cellulaire CD44/CD24/EpCAM et l’activité enzymatique ALDH élevée ont permis d’obtenir un enrichissement significatif en CSC. Toutefois, le niveau de l'activité ALDH est apparu inconstant d’une lignée cellulaire à une autre et selon le type de tumeurs. D'autres marqueurs membranaires ont donné des résultats mitigés dans le cancer du sein ER-. En effet, la plupart des lignées basales ont montré des profils FACS assez homogènes avec des proportions élevées de cellules CD44+. Cependant, l'association de la positivité de CD44 avec l'EMT et la souchitude, ainsi que la bonne corrélation observée dans les modèles luminaux de la population de cellules CD44+/CD24- avec l’enrichissement en CSC, nous a incité à déterminer si le niveau d'expression en CD44 faisait une différence dans les tumeurs basales. Sur cette base, j’ai montré que les cellules CD44 high présentent une forte capacité à former des MS dans toutes les lignées cellulaires testées. Cette constatation nous a incités à utiliser CD44high vs. CD44low comme critère de tri cellulaire et à utiliser ces fractions pour effectuer une analyse du transcriptome afin d'identifier d'autres marqueurs non encore déterminés, pouvant isoler des fractions cellulaires plus faibles avec un enrichissement plus élevé en CSC. / It is now accepted that breast cancer is a compendium of several diseases defined as subtypesthat are associated with different clinical outcomes and molecular characteristics. A betterunderstanding of the mechanisms underlying breast cancer heterogeneity is critical to the development of better adjusted therapies. One of the keys to breast cancer heterogeneity may be explained by cancer stem cells (CSC). A number of markers have been proposed to isolate and characterize breast cancer stem cells, but none appears totally satisfactory.The purpose of my work was determine a marker or combination of markers with which CSC enriched fractions could be reproducibly isolated in basal like breast cancer (BLBC). BLBC represent 15% of all breast tumors, but are the most aggressive subtype. To this aim, I have analyzed a number of markers by FACS analysis and cell sorting and used the capacity to form mammospheres (MS) as a validation criterion for the presence of CSCs. The cell lines used as models were SUM 159, MDA-MB-231, MDA-MB-436, HCC1143, MDA-MB-468, Hs578T and BT-549 comprising both Basal A and Basal B models. I also tested three luminal models MCF7, T47D and BT474.Of all the markers tested those that most consistently allowed enrichment of CSCs were the combination of cell surface proteins CD44/CD24/EpCAM and elevated ALDH enzyme activity. However, ALDH activity appeared irregular, ranging from good to inconsistent according to the cell line. Other cell surface markers gave mixed results in ER- breast cancer because the elevated fraction of CD44+ cells found in most of basal breast cancer cell lines and their propensity to show rather homogenous FACS labeling patterns. However, the association of CD44 positivity with EMT and stemness, as well as the good correlation, we observed in luminal models, of CD44+/CD24- cell population with CSC enrichment incited us to determine whether the level of expression of CD44 could make a difference in basal like models. I show that CD44high cells present higher capacity to form MS in all cell line models tested. This prompted us to use CD44high vs. CD44low as a cell sorting criterion and use these fractions to perform transcriptome analysis in order to identify other markers yet not determined, that may point to smaller cell fractions with a higher CSC enrichment.

La migration cellulaire est un mécanisme important pour divers processus cellulaires tels que l’embryogenèse et la cicatrisation. De même, elle participe à des processus pathologiques notamment l’invasion des cellules malignes et la formation des métastases cancéreux. La dissémination métastatique est un processus très compliqué. L’acquisition du pouvoir migratoire invasif par la cellule maligne ainsi que son potentiel métastatique est gérée par le cytosquelette qui est dynamiquement modifié et contrôlé par des voies de signalisation intracellulaires. Cependant, la physiologie des cellules métastatiques et les cascades de signalisation qui les poussent à métastaser ne sont toujours pas comprises. Les protéines Ezrine, Radixine et Moésine (ERMs) jouent un rôle important dans l’organisation du cytosquelette au cortex cellulaire et elles sont des déterminantes clés de la migration cellulaire. Ainsi, une dérégulation à ce niveau peut conduire à une migration cellulaire aberrante. D’où l’implication des ERMs dans différents cancers agressifs et invasifs. Les ERMs sont régulées en aval de plusieurs acteurs cellulaires notamment les récepteurs membranaires. Plusieurs études ont rapporté que le récepteur au thromboxane A2 (RTXA2), un récepteur couplé à la protéine G (RCPG) favorise les métastases. Il a été décrit surtout dans le cadre de cancer du sein triple négatif (CSTN), l’un des cancers les plus mortels chez la femme. Les RCPG possèdent un rôle central dans presque toutes les fonctions physiologiques et constituent la plus grande famille des cibles médicamenteuses. D’une manière intéressante, les deux laboratoires de Dr Sébastien Carréno et Dr Michel Bouvier, ont découvert que le RTXA2 active les protéines ERMs à travers la GTPase RhoA. Dans ce projet de recherche on a identifié une nouvelle voie de signalisation liant le RTXA2 aux ERMs à travers la GTPase RhoA et la kinase SLK. Cette voie est impliquée dans la migration des cellules de cancer du sein triple négatif. Ainsi, on a pu démontrer que la moésine et la kinase SLK agissaient en aval du récepteur étudié pour favoriser la vitesse et la directionnalité de la migration des cellules de CSTN. 6 On a montré que la migration cellulaire dirigée en aval du RTXA2 est due à une polarité de la moésine au front de la migration. On a constaté aussi que la moésine est responsable d’une polarité des filaments d’actine au front de la migration suite à une activation du récepteur. Ce travail a mis en évidence une nouvelle cascade de signalisation importante pour la migration des cellules cancéreuses agressives triples négatives du sein ce que pourrait être une nouvelle cible des thérapies anti-métastatiques. / Cell migration is an important mechanism for various cellular processes such as embryogenesis and cicatrization. Likewise, it controls pathological processes including the invasion of malignant cells and the formation of metastases. Metastasis is a very complicated process. The acquisition of invasive migratory power by a malignant cell as well as its metastatic potential is regulated by the cytoskeleton which is dynamically modified and controlled by intracellular signaling pathways. However, metastatic cells physiology and the cascades causing their metastases are not clear yet. Ezrin, Radixin and Moesin (ERMs) proteins have an important role in organizing the cytoskeleton at the cell cortex and they are key determinants of cell motility. Thus, a deregulation at this point may lead to an aberrant cell migration. Hence, the involvement of ERMs in various aggressive and invasive cancers. ERMs are regulated downstream of several cellular actors in particular membrane receptors. Several studies have reported that the thromboxane A2 receptor (TXA2R), a G protein coupled receptor (GPCR) promotes metastasis. It has been described especially in the context of triple negative breast cancer (TNBC), one of the deadliest cancers in women. GPCR have a central role in almost all physiological functions and constitute the largest family of drug targets. Interestingly, the two laboratories of Dr Sébastien Carréno and Dr Michel Bouvier, have discovered that the TXA2R activates ERM proteins through the GTPase RhoA. In this research project, we have identified a new signaling pathway linking the TXA2 receptor to ERMs via RhoA and the kinase SLK. This pathway is involved in the migration of triple negative breast cancer cells. Thus, we demonstrated that moesin and SLK acted downstream of the receptor to promote the speed and directionality of TNBC cells migration. We discovered that the directed cell migration downstream of TXA2R is due to a polarization of moesin at the leading edge. We also observed that moesin is responsible for actin filaments polarity at the leading edge following an activation of the receptor. So, this work has revealed a new signaling cascade important for the migration of aggressive triple negative breast cancer cells which could be a new target for anti-metastatic therapies.

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About 12 to 17 percent of all breast cancers are triple-negative breast cancer (TNBC). In TNBC, estrogen, progesterone, and human epidermal growth factor receptor two are not expressed, or copies of the HER2 gene are decreased (or both). This makes TNBC hard to treat in comparison with other kinds of breast cancers. New studies have made some interesting observations on how some monoclonal antibodies can help to treat TNBC. One of the monoclonal antibodies that can be useful for treating TNBC is pembrolizumab. Pembrolizumab inhibits programmed death ligand 1 (PD-1), which is located on the surface of T cells from connecting to immune checkpoint proteins such as programmed death ligand 1 (PD-L1) and programmed death ligand 2 (PD-L2) located on the surface of the cancer cell. Breaking this connection enables continued activation of T cells and attack of the cancer cells. This thesis aimed to evaluate if pembrolizumab was safe and effective as monotherapy or as a combination therapy with chemotherapy for patients with different stages of TNBC. This study was based on scientific articles identified from the database PubMed. Five randomized controlled trial studies were selected for further study in this project. Two publications were chosen from keynote-355, which studied the effect and safety of Pembrolizumab in combination with chemotherapy and compared it to chemotherapy monotherapy in patients with metastatic TNBC. The first study included patients from different countries as it was a multi-center study, and the second one focused only on patients who enrolled in Japan. One study was chosen from keynote-119 studies, which compared health-related quality of life for patients who were treated with pembrolizumab monotherapy or with monotherapy of chemotherapy. The last two articles which were chosen were about keynote-522. The first article about keynote-522 compared was a multicenter study enrolled in 21 countries. In this study, patients had early-stage TNBC and received neoadjuvant placebo chemotherapy or pembrolizumab chemotherapy. After the breast operation, either adjuvant pembrolizumab or placebo was received. The other study looked at Asian patients who enrolled in keynote-522. Results showed that monotherapy with pembrolizumab did not make a massive difference in overall survival compared to chemotherapy. Still, it led to better health- related quality of life for patients (Combined Positive Score (CPS) ≥ 10) treated with pembrolizumab. Results from keynote-355 showed that combination therapy with pembrolizumab and chemotherapy led to better and longer progression-free survival and overall survival in patients with CPS ≥ 10 treated with pembrolizumab. The analysis of Japanese patients showed even better progression-free survival and overall survival results than the global population. The study from keynote-522 showed that neoadjuvant pembrolizumab and chemotherapy followed by adjuvant pembrolizumab had a better effect than only neoadjuvant chemotherapy. The second keynote-522 study showed the same results as the global study and better results at event-free survival for the Asian population than the overall population. After reviewing the articles, it was found that pembrolizumab proves to be a safe and effective treatment for TNBC. To enhance understanding of the drug's effects, measures such as extending follow-up periods, conducting further studies to assess its effectiveness, and exploring new research methodologies are proposed.

Bioimpedance presents a versatile, label-free means of monitoring biological cells and their responses to physical, chemical and biological stimuli. Breast cancer is the second most common type of cancer among women in the United States. Although significant progress has been made in diagnosis and treatment of this disease, there is a need for robust, easy-to-use technologies that can be used for the identification and discrimination of critical subtypes of breast cancer in biopsies obtained from patients. This dissertation makes contributions in three major areas towards addressing the goal. First, we developed miniaturized bioimpedance sensors using MEMS and microfluidics technology that have the requisite traits for clinical use including reliability, ease-of-use, low-cost and disposability. Here, we designed and fabricated two types of bioimpedance sensors. One was based on electric cell-substrate impedance sensing (ECIS) to monitor cell adhesion based events and the other was a microfluidic device with integrated microelectrodes to examine the biophysical properties of single cells. Second, we examined a panel of triple negative breast cancer (TNBC) cell lines and a hormone therapy resistant model of breast cancer in order to improve our understanding of the bioimpedance spectra of breast cancer subtypes. Third, we explored strategies to improve the sensitivity of the microelectrodes to bioimpedance measurements from breast cancer cells. We investigated nano-scale coatings on the surface of the electrode and geometrical variations in a branched electrode design to accomplish this. This work demonstrates the promise of bioimpedance technologies in monitoring diseased cells and their responses to pharmaceutical agents, and motivates further research in customization of this technique for use in personalized medicine. / Ph. D.

The rationale behind targeted molecular therapy in cancer, oncogene addiction, is that tumors rely on driver oncogenes to control their proliferation and survival. Therefore, an efficacious targeted therapy should induce a dual, detrimental response to the tumor. While there have been clinical success stories using targeted therapies, even tumors that are initially sensitive invariably develop resistance. In the case of triple negative breast cancer (TNBC), despite extensive evidence pointing to its driver oncogene status, inhibitors of the Epidermal Growth Factor Receptor (EGFR) are considered clinically inefficacious. Resistance to EGFR inhibition has been predominantly described as due to genetic alterations. Yet it remains unclear why patients exhibiting the same dysregulated status of a driver oncogene react to targeted therapy, as in the case of EGFR-mutant non-small cell lung cancer, while others do not at all (i.e., TNBC). Furthermore, not all of resistance can be described by genetic alterations to EGFR, to its pathway effectors, or to compensatory pathways. Emerging data reveals that drugs can induce resistance by rewiring epigenomic, transcriptional, and translational regulatory mechanisms. Unfortunately, a major limitation in designing efficacious treatments is our inability to predict whether cell types can rewire in response to drug exposure. Therefore, it is necessary to elucidate mechanisms of growth and survival in cells that have undergone rewiring. This study characterized intrinsic resistance to EGFR inhibition in TNBC. We found that EGFR inhibition induces rewiring, which results in a resistant growth state that bypasses the EGFR-MAPK pathway as a whole. Additionally, we found that a tRNA-modifying complex masks the oncogene addiction status of EGFR in TNBC by stabilizing the protein abundance of a pro-survival protein. Importantly, this happens solely in the context of EGFR inhibition. Taken together, this study highlights potential therapeutic strategies for TNBC and strategies that can be used to improve our understanding of targeted therapy resistance, especially intrinsic resistance.

Magister Scientiae (Medical Bioscience) - MSc(MBS) / Purpose: Breast cancer is one of the most frequent and fatal diseases women all around the globe are challenged with today. In women, breast cancer has the highest mortality rate of all cancers and the incidence rate is on the increase. It is estimated that by the year 2025, 19.3 million women will become a victim of this grave health problem. This disease is a result of the formation of malignant tumours caused by genetic alterations that are involved in the proliferation of cells, cellular differentiation and the disturbance in homeostasis which subsequently leads to the abnormal multiplication and growth of cells. Breast cancer is considered a multifactorial disease with various risk factors such as age, radiation exposure, hormone therapy, oral contraceptives, dietary factors, environmental exposure and genetic predispositions. Breast cancers can be subdivided and classified based on their cellular surface receptors such as Estrogen Receptors, Progesterone Receptors and Human Epidermal Growth Factor Receptor 2. Of the various subtypes, the triple-negative breast cancer subtype which is negative for all 3 surface receptors and presents as the most aggressive form of breast cancer with a poor prognosis. Between 10-20% of all breast cancer cases are classified as triple-negative breast cancer. Due to the hormonal status of triple-negative breast cancer, treatment options are limited and thus of great concern. Chemotherapy remains the most common treatment modality, but prognosis is poor with relapse within years ultimately leading to poor survival outcome. Due to this lack of effective treatment plans, an alternative treatment with minimal side effects and better survival remains an imperative area to explore. A wide scope of literature highlights red palm oil and its health benefits, with its growth inhibitory potential drawing great attention. Red palm oil, extracted from the Elaeis guineensis palm tree is red in colour due to the abundance of carotenoids, tocotrienols and tocopherols found in the oil. Various compounds make up the oil such as lycopene, carotenes, vitamin E and coenzyme Q10. Most studies have researched the effects of vitamin E extracted from the oil as a contributor to its growth inhibitory activity. This study focuses on the effects of the commercial red palm oil as a whole with all its compounds on the proliferation of breast cancer cells as well as the effect it has on various genes associated with breast cancer. Method: This study investigated the effect of red palm oil concentrations (1, 10, 100, 500 and 1000 μg/ml) on breast cancer cells—MCF-7 and MDA-MB-231 with comparison to a non-cancerous cell line—MCF-12A for 24-, 48- and 72-hour treatment periods. The parameter investigated was cell proliferation through the CCK-8 cell proliferation assay and the morphology following red palm oil treatment was observed and captured. Additionally, this study also investigated the effect of red palm oil on the expression of Human Mammaglobin (hMAM) and Maspin genes through the PCR assay and results visualised through agarose gel electrophoresis. Data was statistically analysed using GraphPad version 6.0 software. Results: Following treatment of red palm oil, no apparent changes in the cell morphology was observed despite using variable treatment concentrations over variable times for MCF-7, MDA-MB-231 and MCF-12A cells relative to their respective controls. Immortalised MCF-12A cells showed a significant increase in proliferation with the varying treatment concentrations, but more prominently with the highest concentration at 24, 48 and 72 hours. MCF-7 cells showed significant decreases at 24 and 72 hours. Decreased proliferation was observed at all dosages used, particularly at 10, 100, and 500 μg/ml. Furthermore, MDA-MB-231 cells demonstrated a gradual increase in cell proliferation for the 3 selected time periods in the varying concentrations. Additionally, red palm oil did not alter the gene expression of Maspin at any of the varying treatments for MDA-MB-231 nor MCF-7 cells. However, changes in hMAM gene expression were observed at treatment concentration of 100 μg/ml in MDA-MB-231 cells that were incubated for 24 and 48 hours. However, the hMAM expression was not affected in treated MCF-7 cells. Conclusion: Red palm oil, as an alternative dietary oil, seems to have potential growth inhibitory properties as demonstrated by the change in the cell proliferation of the MCF-7 cells. Literature show that various individual compounds extracted from red palm oil have anti-proliferative and inhibitory effects on breast cancer cells making them good candidates for therapy. However, this study concludes that red palm oil as a whole component would not be a suitable therapeutic agent for highly aggressive triple-negative breast cancer.

La chimiothérapie cytotoxique reste une option de traitement de première intention pour la majorité des cancers. Un effet secondaire majeur dans les schémas chimio-thérapeutiques est la neutropénie. La thérapie prophylactique avec le facteur de stimulation des colonies de granulocytes (G-CSF), une cytokine endogène responsable de la régulation de la production de neutrophiles, est administrée en concomitance. Le moment et la dose exacts pour administrer la chimiothérapie et le G-CSF représentent des éléments cruciaux pour obtenir les résultats souhaités du traitement. En nous appuyant sur des travaux antérieurs qui optimisaient les schémas thérapeutiques du G-CSF, nous sommes basés sur une approche de pharmacologie quantitative des systèmes (QSP) pour étudier la fréquence et l’intensité de la dose dans le but de maximiser les effets anti-tumoraux de la chimiothérapie tout en minimisant la neutropénie. Dans ce travail, nous avons effectué une optimisation sur une large gamme de longueurs de cycle et de valeurs des doses de chimiothérapie afin d’identifier les meilleurs schémas en combinaison avec le G-CSF. Nos résultats suggèrent que la doxorubicine 45mg/BSA tous les 14 jours a un impact positif sur le contrôle de la croissance tumorale, et qu’il est préfèrable de retarder l’administration du G-CSF au septième jour après la chimiothérapie et de donner moins de doses pour minimiser le risque de neutropénie et le fardeau de ce médicament. Cette étude suggère des pistes possibles pour des schémas optimaux de chimiothérapie, avec le soutien prophylactique du G-CSF spécifiquement dans le contexte du cancer du sein triple négatif. / Cytotoxic chemotherapy continues to be a first-line treatment option for the majority of cancers. A major side effect in chemotherapy regimens is neutropenia. Prophylactic therapy with granulocyte colony stimulating factor (G-CSF), an endogenous cytokine responsible for regulating neutrophil production, is administered concomitantly; the exact timing of the combination chemotherapy and G-CSF is crucial for achieving treatment results. Leveraging on previous work that optimized treatment regimens based on G-CSF timing, we developed a quantitative systems pharmacology (QSP) framework to study dose frequency and intensity of chemotherapy in order to maximize anti-tumor effects while minimizing neutropenia. In this work, we performed an optimization across a wide range of cycle lengths and dose sizes to identify the best cytotoxic chemotherapy regimens with G-CSF support. Our results suggest that doxorubicin 45mg/BSA every 14 days, has a positive impact on tumour growth control, and that to minimize the risk of neutropenia and the burden to patients it is best to delay the administration of G-CSF to day seven after chemotherapy and give fewer doses . This study suggests possible avenues for optimal chemotherapy regimens with prophylactic support of G-CSF in the context of Triple Negative Breast Cancer.

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