Les cancers moléculaires apocrines sont un sous-groupe de cancer du sein caractérisé par l'expression du récepteur aux androgènes (RA), l'absence du récepteur aux oestrogènes (RE) et l'expression paradoxale de nombreux gènes typiquement exprimés dans les tumeurs RE positives. Une proportion significative de ces patientes va récidiver sous forme de métastases dont la prise en charge repose sur des traitements non spécifiques (chimiothérapies). En préclinique, la lignée cellulaire MDA-MB-453 a été identifiée comme ayant un profil transcriptomique similaire à ce sous-groupe tumoral. En clinique, les essais réalisés dans ce sousgroupe tumoral avec différents anti-androgènes, dont l’abiratérone (inhibiteur de la synthèse des androgènes), retrouvent un bénéfice clinique chez environ 25% des patientes. L’objectif de cette thèse est d’améliorer les connaissances et les prises en charge thérapeutiques spécifiques de ces tumeurs. Nos données précliniques comparatives montrent que l'ODM-201, nouvel antiandrogène, ne présente pas une efficacité supérieure par rapport aux antiandrogènes déjà étudiés. Afin de contourner les limites des lignées cellulaires identifiées dans ce premier projet, nous avons démontré la nécessité de développer de nouveaux modèles : les Patient-Derived-Xenograft orthotopiques. Notre deuxième projet est en faveur d’une meilleure sélection des patientes à traiter par abiratérone notamment basé sur des caractéristiques immunohistochimiques apocrines. Chez les patientes ne présentant pas ces caractéristiques, nous avons isolé CHEK1 comme une cible d’intérêt en combinaison thérapeutique pour majorer les taux de réponse de l’abiratérone en monothérapie. / Molecular apocrine cancers are a subgroup of breast cancer characterized by the expression of the androgen receptor (AR), the absence of the estrogen receptor (ER) and the paradoxical expression of many genes typically expressed in ER positive tumors. A significant proportion of these patients will recur in the form of metastases whose management is based on non-specific treatments (chemotherapy). In preclinical study, the MDA-MB-453 cell line was identified as having a transcriptomic profile similar to this tumor subgroup. Clinical trials in this tumor subgroup testing different antiandrogens, including abiraterone (inhibitor of androgen synthesis), found a clinical benefit in about 25% of patients. The aim of this thesis is to improve the knowledge and the specific therapeutic management of these tumors. Our comparative preclinical data show that ODM-201, a new anti-androgen, does not show superior efficacy compared to previously studied anti-androgens. In order to circumvent the limits of cell lines provided by this first project, we have shown the need to develop new models: orthotopic Patient-Derived-Xenograft. Our second project favors a better selection of patients to be treated with abiraterone, especially based on apocrine immunohistochemical characteristics. In patients without these characteristics, we isolated CHEK1 as a target of interest in combination therapy to increase response rates of abiraterone monotherapy.

MicroRNAs are a class of small non-coding RNAs involved in post-transcriptional regulation. Their role in almost all processes of the cell, make microRNAs ubiquitary players of cell development, growth, differentiation, cell to cell communication and cell death. Thus, cells’ physiological or pathological conditions are reflected by variations in the levels of expression of microRNAs, enabling them to be used as biomarkers of such states. In the past decade, there has been an exponential increase of studies using microRNAs as potential biomarkers for cancer, neurodegenerative diseases, inflammation and cardiac diseases, from tissues and liquid biopsies. However, none of them has reached the clinics yet, due to inconsistency of results through the literature and lack of assay standardization and reproducibility. Technological limitations of microRNAs detection have been, to date, the biggest challenge for using these molecules in clinical settings. In fact, although microarrays, RT-qPCR and RNA-seq are well-established technologies, they all require complex procedures and trained personnel, for performing RNA extraction, labelling of the target and PCR amplification. All these steps introduce variability and, in addition, since no universally standardized protocol – from sample extraction to analyte detection - has been produced yet, methodological procedures are difficult to reproduce. For this reason, we developed a new platform for the rapid detection of microRNAs in biofluids composed of an innovative silicon-photomultiplier (SiPM) based detector and a new chemistry for nucleic acid testing (Chem-NAT). Chem-NAT exploits a dynamic labelling chemistry which allows the sensitive detection of nucleic acids till single base level. On the other hand, SiPM-based device, compared to normal vacuum photomultipliers, grants miniaturization and higher capacity of fitting in a bench-top solution for clinical settings, among other advantages. The new platform – ODG – has been validated for the direct detection – neither RNA extraction nor PCR amplification needed - of microRNA-21 in plasma of lung cancer patients. In this work, we also explored the use of microRNAs as biomarkers in metastatic castration resistant prostate cancer (mCRPC). We collected plasma samples from mCRPC patients before and after abiraterone acetate treatment – androgen deprivation type of drug – and performed a miRnome analysis for discovering microRNAs predicting the efficacy of the drug. We chose miR-103a-3p and miR-378a-5p and we validated them via TaqMan RT-qPCR. We discovered that the ratio between the two microRNAs is able to predict the efficacy of abiraterone acetate and follow the responsiveness in time. In liquid biopsies, extracellular vesicles are getting increasing importance for diagnostic and prognostic purposes. Therefore, in this work we also explored the expression of some microRNAs in extracellular vesicles from plasma, isolated via nickel-based method. We discovered that microRNA-21 and microRNA-223 are not enriched in vesicles from healthy individuals.