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UBC Theses and Dissertations

The role and relevance of exosomes in the development and progression of prostate cancer Hosseini-Beheshti, Elham


Prostate cancer (PCa) is the leading diagnosed cancer in men. Prompt diagnosis of the disease can substantially improve its clinical outcome. Improving capability for early detection and developing new therapeutic targets in advanced disease are research priorities that will ultimately lead to better patient survival. Eukaryotic cells secrete proteins via distinct regulated mechanisms, which are either ER/Golgi dependent or microvesicle-mediated. The release of microvesicles has been shown to provide a novel mechanism for intercellular communication. Exosomes are nanometer-sized membrane-vesicles, which are secreted from normal/cancerous cells. They are present in various biological fluids. Recent studies have demonstrated that cancerous cells secret exosomes, which may be differentiated from those, derived from normal cells based on their composition. The main hypothesis for this Ph.D. thesis is to assess exosomes as potential diagnostic biomarkers for PCa diagnosis and investigate the role of exosomes in PCa progression. In this study, exosomes were purified from the conditioned media of six different prostate cell lines and biological fluids obtained from PCa patients. Analysis using NanosightTM, western blot and transmission-electron-microscopy validated the size, purity and integrity of isolated exosomes. Uptake by different PCa cell lines, following exposure to exosomes, was confirmed using confocal microscopy. Proteomic analysis of isolated exosomes was performed using a Waters LC-QTOF/MS in conjunction with ProteinLynx and MASCOT software. In addition to possible underlying differences in protein profiles an additional part of this study investigated the lipid profiles and cholesterol levels in exosomes as further potential diagnostic markers. Our results have also confirmed the influence of PCa derived exosomes with different functional assays including apoptosis, proliferation and migration. Finally we demonstrated the effect of PCa cells derived exosomes in vivo, and their influence on tumor growth using a human xenograft animal model of PCa. The results of this study have highlighted a potential for the differential protein/lipid composition of exosomes to be a source of diagnostic biomarkers for PCa amenable via non-invasive testing. Our experimental evidence also indicates that exosomes with different androgen receptor phenotypes attribute positively in many mechanisms that contribute to PCa progression presenting additional insight into exploratory research for novel therapeutic targets.

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