Le cancer du sein de phénotype « Basal-like » triple négatif (BLTN) est particulièrement agressif et de mauvais pronostic. Il est insensible aux traitements hormonaux laissant pour seule stratégie de traitement la chimiothérapie conventionnelle. De ce fait, de nouvelles thérapeutiques ciblées sont en développement, tels que les inhibiteurs de la Poly-ADP-Ribose-Polymerase (PARP). Dans ce contexte, nos travaux de recherche ont été orientés sur l’optimisation du traitement des cancers du sein BLTN en modélisant l’action d’un anti-PARP modèle, l’Olaparib sur la lignée SUM1315 de phénotype BLTN. Dans un premier temps, l’étude de la coexpression de la BCRP et de la P-gp, deux protéines « Multidrug Resistance » (MDR) majeures en présence de 50 µM d’Olaparib® a montré une induction de leurs expressions chez les cellules SUM1315, avec une réponse de type relais. La BCRP établirait une première ligne de défense cellulaire et son action serait ensuite relayée par la P-gp durant 24h de traitement. Ce mécanisme est en corrélation avec la concentration intracellulaire d’Olaparib mesurée par HPLC. L’ensemble de nos résultats suggère qu’il serait possible de contourner le mécanisme de résistance induit par les protéines MDR si une concentration stable en Olaparib est maintenue dans les cellules à long terme. Nous avons ensuite étudié la potentialisation de l’action de l’Olaparib en le combinant avec un traitement par radiothérapie à basse et haute énergie, sur la viabilité des cellules de la lignée SUM1315. La comparaison des résultats avec un traitement Olaparib seul ou irradiation seule et ceux des traitements combinés Olaparib/radiothérapie a alors mis en évidence un effet synergique des deux traitements sur la viabilité cellulaire. L’effet synergique de cette combinaison fonctionne même avec de faibles doses d’Olaparib. De cette manière, il serait possible de réduire les doses d’anti-PARP utilisées tout en gardant les bénéfices du traitement. Enfin, nous avons développé deux techniques de cultures cellulaires en trois dimensions (i) « hanging drop » et (ii) « liquid overlay », permettant de mimer plus fidèlement les conditions des tumeurs in vivo. L’observation en microscopie électronique à transmission et à balayage des sphéroïdes obtenus par ces deux techniques a permis de démontrer l’intégrité des cellules au sein des sphéroïdes ainsi que la formation de jonctions cellulaires. Cependant, les sphéroïdes obtenus en « liquid overlay » ont montré une meilleure intégrité ultra-structurale. / « Triple Negative Basal-Like » (BLTN) breast cancer is particularly aggressive and of poor prognosis. It is insensitive to hormone-targeted therapies leaving conventional chemotherapy as the only treatment strategy. Therefore, new promising targeted therapies are being developed, such as Poly-ADP-Ribose-Polymerase inhibitors (anti-PARPs). In this context, our research has been directed towards optimizing the treatment of BLTN breast cancer by modelling the action of an anti-PARP model, Olaparib®, on BLTN cell line SUM1315. Firstly, the study of the co-expression of BCRP and P-gp, two major “Multidrug Resistance” proteins (MDR) in the presence of 50 µM Olaparib® showed an induction of their expression in SUM1315 cells, with a relay-type response. BCRP would establish a first line of cellular defense and its action would then be taken over by P-gp, for 24h of treatment. This mechanism is correlated with the intracellular concentration of Olaparib® measured by HPLC. All of our results suggest that it would be possible to circumvent the induced MDR resistance mechanism if a stable concentration of Olaparib® is maintained in cells in the long term. Secondly, we studied the potentiation of the action of Olaparib® combining it with low and high-energy radiations on the viability of SUM1315 cells. Comparison of the results with single Olaparib®, single irradiation, or the combination of Olaparib®/radiotherapy then demonstrated a synergistic effect of the two treatments when delivered concomitantly, on cell viability. The synergistic effect of this combination works even with low doses of Olaparib®. In this way it would be possible to reduce the anti-PARP doses while maintaining the benefits of this treatment. Finally, we have developed two techniques of cell culture in three dimensions: (i) "hanging drop" and (ii) "liquid overlay", in order to mimic more accurately the conditions of tumours in vivo. Observations of spheroids obtained by these two techniques by transmission and scanning electron microscopy demonstrated the integrity of cells within as well as the formation of cell junctions. However, the spheroids obtained by "liquid overlay" showed better ultra-structural integrity.

Quatorze femmes canadiennes meurent chaque jour du cancer du sein. Le cancer du sein triple-négatif (CSTN) détient un mauvais pronostic De nombreux efforts sont fournis afin d'offrir à ces patientes des traitements ciblés, comme les inhibiteurs de poly (adenosine diphosphate-ribose) polymerase inhibitors (PARPi) afin d’améliorer leur survie et de minimiser la toxicité liée à la chimiothérapie. Le sous-groupe de CSTN qui pourrait bénéficier des PARPi reste à être identifié. De plus, différentes stratégies d'administration des PARPi et de la chimiothérapie pourraient améliorer leur efficacité thérapeutique tout en diminuant la toxicité. Nous avons précédemment dérivé une signature génétique de 63 gènes prédisant la réponse aux PARPi avec une précision globale élevée. Nos objectifs sont 1) d'évaluer les implications cliniques de la signature génétique; et 2) de déterminer la séquence optimale d'administration du talazoparib et du carboplatin in vivo en cancer du sein triple-négatif BRCAWT. D'abord, nous avons évalué la fréquence mutationnelle des 63 gènes dans différents contextes cliniques. Deux bases de données publiques furent utilisées. Puis, nous avons comparé trois cohortes de xénogreffes orthotopiques: A) talazoparib en premier, combiné au carboplatin le jour 3; carboplatin en premier suivi du talazoparib B) un jour après; et C) sept jours après. La fréquence mutationnelle des 63 gènes était élevée chez les tumeurs luminales B et celles de mauvais pronostic. Les patientes luminales B mutées avaient une moindre survie que les patientes non mutées. Aussi, l'inhibition tumorale et métastatique était similaire pour les cohortes A et B, cependant la cohorte B avait moins de toxicité. Les PARPi pourraient avoir un rôle chez les tumeurs luminales B et celles de mauvais pronostic. Deuxièmement, le prétraitement avec le carboplatin semble améliorer la sensibilité au talazoparib et diminuer la toxicité. / Fourteen Canadian women die every day from breast cancer. Triple-negative breast cancer (TNBC) has a poor prognosis. Numerous efforts are made to offer these patients targeted therapies such as poly (adenosine diphosphate-ribose) polymerase inhibitors (PARPi) to improve survival and minimize chemotherapy-related toxicity. It is not well understood which subset of TNBC patients will benefit from PARPi; and if different sequencing strategies of PARPi and chemotherapy can improve therapeutic efficacy and decrease toxicity. We previously derived a 63-gene signature predicting response to PARPi with a high overall accuracy. Our objectives are 1) to evaluate the clinical implications of the 63-gene signature; and 2) to determine the optimal sequence of administration of talazoparib and carboplatin in vivo in BRCAWT TNBC. First, we evaluated the mutational frequency of the 63 genes in different clinical settings using two publically-available datatsets. Second, we compared three cohorts of orthotopic xenografts: A) talazoparib first, combined with carboplatin on day 3; carboplatin first, followed by talazoparib B) one day later; and C) seven days later. We found that the mutational frequency was high in breast cancer subtypes of poor prognosis. Mutated luminal B patients had a lower survival than non-mutated patients. We also found that tumoral and metastatic inhibition were similar between cohorts A and B, but cohort B had less toxicity. In conclusion, there is potential for PARPi efficacy in luminal B and poor prognosis tumors. Second, pretreatment with carboplatin may be an effective approach with less toxicity.

<p>With 2.1 million new cases, breast cancer is the most common cancer in women. Triple negative breast cancer (TNBC), which is 15-20% of these breast cancer cases is clinically negative for expression of estrogen and progesterone receptors (ER/PR) and human epidermal growth factor receptor 2 (HER2) receptors<a>.</a> It is characterized by its unique molecular profile, aggressive behavior, distinct patterns of metastasis, and lack of targeted therapies. TNBCs utilize glycolysis for growth, proliferation, invasiveness, chemotherapeutic resistance and hence has poor therapeutic response. There is an urgent need for novel/alternate therapeutic strategies beyond current standard of treatment for this subset of high-risk patients. Electrical pulse-based chemotherapy, known as electrochemotherapy (ECT) could be a viable option for TNBC therapy. ECT involves the local application of precisely controlled electrical pulses to reversibly permeabilize the cell membrane for enhanced uptake. ECT can increase the cytotoxicity of the chemotherapeutics up-to 1000 times, facilitating a potent local cytotoxic effect. </p> <p>The high cost and severe side-effects of conventional chemotherapeutics motivate the application of effective natural compounds. Combining electrical pulses with natural compounds will enhance the treatment efficacy. This dissertation focuses on curcumin, the yellow pigment of natural herb turmeric, that has been used for over 5000 years for its excellent anticancer properties. Previous studies have demonstrated the effectiveness of curcumin for treating multiple cancers, including TNBC, with limited side effects. The potency of curcumin can be enhanced further by combining it with ECT to provide an attractive and cost-effective alternative for TNBC treatment. </p> <p>Towards this we studied the effect of ECT with curcumin on MDA-MB-231 cell line, a human adenocarcinoma epithelial TNBC cell line. We performed various assays, including cell viability, colony forming, cell cycle, apoptosis, H₂O₂ reactive oxygen species (ROS), immunoblotting, real time quantitative PCR (qPCR), and cellular metabolites detection to study the impact of ECT with curcumin on MDA-MB-231 cells. In addition, to better understand the underlying mechanisms, we used high throughput, label-free quantitative proteomics. While several studies have attempted to define the mechanism of action of curcumin on cancer cells, little is known on the action mechanism of the curcumin delivered with electrical pulses. This work unravels the molecular mechanism behind the enhanced effects observed under the ECT-based curcumin therapy in TNBC cells, employing a high-throughput, quantitative, label-free mass spectroscopy-based proteomics approach. The proteomics approach provides information on the thousands of cellular proteins involved in the cellular process, allowing a comprehensive understanding of the electro-curcumin-therapy mechanism. Similar studies were also performed for ECT with cisplatin to compare the efficacy of the electro-curcumin-therapy to the standard stand-alone cisplatin-based therapy.</p> <p>Our results revealed a switch in the metabolism from glycolysis to mitochondrial metabolic pathways. This metabolic switch caused an excessive production of H₂O₂ ROS to inflict apoptotic cell death in MDA-MB-231 cells, demonstrating the potency of this ECT based curcumin therapy. These results encourage further studies to extend the application of ECT for clinical practice.</p>

Breast cancer, as the most prevalent cancer in women, is responsible for more than 15% of new cancer cases and about 6.9% of all cancer-related death in the US. A major cause of therapeutic failure in breast cancer is the development of resistance to chemotherapy, especially for triple-negative breast cancer (TNBC). Therefore, how to overcome chemoresistance is the major challenge to improve the life expectancy of breast cancer patients. Our studies demonstrate that TNBC cells surviving the chronic treatment of chemotherapeutic drugs show significantly higher expression of the dual serine/threonine and tyrosine protein kinase (DSTYK) than non-treated parental cells. In our in vitro cellular models, DSTYK knockout via the CRISPR/Cas9-mediated technique results in apoptotic cell death of chemoresistant cells upon drug treatment. Moreover, DSTYK knockout promotes chemotherapeutic drug-induced tumor cell death in an orthotopic mouse model. These findings suggest that DSTYK exerts an important and previously unknown role in promoting chemoresistance. Our studies provide fundamental insight into the role of DSTYK in chemoresistance in TNBC cells and lay the foundation for the development of new strategies targeting DSTYK for improving TNBC therapy.

Trippelnegativ bröstcancer (TNBC) är den mest maligna formen av bröstcancer utan någon framträdande behandlingsbar biomarkör. Således har den djupa återfallsfrekvensen och bristen på behandlingsalternativ öppnat behovet av att förstå TNBC: s etiopatogenes och molekylära mekanism. Huvudsyftet är att kartlägga det genomomfattande differentiella uttrycket av den förmodade cancergenen (en prenyleringsgen) och dess betydelse vid trippelnegativ bröstcancer. Hi-Cap (Capture Hi-C) är en teknik som genererar högupplösta promotor-förstärkare interak- tioner med nästan en-förstärkare upplösning.Vi arbetade med cancercellinjer, MDA-MB_231, med och utan den förmodade genen. Hi-C-tekniken optimerades i enlighet därmed för cancer- cellinjen för att generera en högupplöst berikad region. Resultaten kan vidare användas för att utföra biblioteksförberedelser och bioinformatikanalys. Dessa fynd kommer att ägnas åt att upptäcka nya vägar involverade i prenylering och TNBC. / Triple-negative Breast cancer (TNBC) is the most malignant form of breast cancer with no prominent treatable biomarker. The profound recurrence rate and lack of treatment options have opened the need to understand the etiopathogenesis and molecular mechanism of TNBC. The main objective of this study is to map the genome-wide differential expression of the putative cancer gene (a prenylation gene) and its importance in Triple-Negative Breast cancer. Hi-Cap (Capture Hi-C) is a technique which generates high-resolution promoter-enhancer interactions with almost single-enhancer resolution. We worked with cancer cell lines, MDA-MB_231, with and without the putative gene. The Hi-C technique was optimized accordingly for the cancer cell line to generate a high-resolution enriched region. The results can be further used to perform library prep and bioinformatics analysis. These findings will devote to discovering novel pathways involved with prenylation and TNBC.