Abstract 1527: Investigation the role of prostate cancer derived exosomes on their tumor microenvironment.

Introduction: Prostate cancer (PCa) is the leading type of cancer diagnosed in men. In 2012, approximately 241,740 new cases of PCa will be diagnosed in the United States. Prompt diagnosis of the disease can substantially improve its clinical outcome. Improving capability for early detection, as well as 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 cup-shaped membrane vesicles which are secreted from normal and cancerous cells. They are present in various biological fluids such as serum, milk, urine, malignant ascites and amniotic fluid. Recent studies have demonstrated that cancerous cells secret exosomes which may be differentiated from those derived from normal cells upon their composition. Therefore, exosomes could be used in facilitating early diagnosis via less invasive procedures or be candidates for novel therapeutic approaches for different pathological disorders. Studies on tumour-related microvesicles suggest that exosomes play a significant role in paracrine signaling pathway thus potentially influencing cancer progression via different mechanisms. Methods and Results: Exosomes were purified from the conditioned media (CM) from different PCa cell lines after 72 hours in serum free media treatment. Using differential centrifugation cell debris and protein aggregates were removed from CM. Finally exosomes were isolated in a 30% sucrose cushion using ultracentrifugation. Further analysis using transmission electron microscopy validated the integrity of purified exosomes. Western blot analysis was also used to probe for different exosome markers. Proteomic mass spectrometry of exosomes reveals that exosomes derived from specific PCa cells present potential markers of PCa progression. Transfer of exosomes to non-identical cells in culture was visualised using confocal microscopy of fluorescence labeled exosomes as well as exosomal GFP tagged protein. Phenotypic change in recipient cells was studied upon exposure to exosomes derived from non-identical prostate cell lines and an impact on cell survival pathways associated with tumor microenvironment were observed. Conclusion: This study revealed that PCa derived exosomes represent a conduit for protein/genetic information transfer into their tumor microenvironment conferring pro-cell survival and metastasis. Citation Format: Elham Hosseini-Beheshti, Christine Liu, Hans Adomat, Emma S. (Tomlinson) Guns. Investigation the role of prostate cancer derived exosomes on their tumor microenvironment. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 1527. doi:10.1158/1538-7445.AM2013-1527