Characterization And Comprehensive Proteomic Analysis Of Exosomes Derived From Prostate Cancer Cell Lines

Proceedings: AACR 102nd Annual Meeting 2011‐‐ Apr 2‐6, 2011; Orlando, FL Background: Exosomes are extracellular nano-vesicles which are secreted upon fusion of multivesicular bodies with the plasma membrane and present in most body fluids. They have been shown to be derived from a multitude of cell types and, while it is postulated that they are important for membrane trafficking as communication vesicles, their relevance in cancer and specifically prostate tumour growth and progression has yet to be determined. Factors such as stage of cancer, cell type and cell cycle could affect the amount and composition of exosomes formed and secreted. While the mechanisms underlying exosome formation and secretion are not fully understood, characterization of exosomes derived from different androgen dependent and independent prostate cancer cell lines (LNCaP, C4-2, VCaP, DU-145, PC-3) versus normal epithelial prostate cell line (RWPE-1) indicate novel information about their possible role in prostate cancer. In Addition proteomic analysis of exosomes derived from different prostate cancer cell lines reflects differential protein content within these entities and could be considered for prognostic potential. Other studies on tumour-related microvesicles suggest the role of these selectively enriched exosomes in cancer progression therefore the presence of differential protein markers in and on prostate cancer cell derived exosomes may yield potential biomarkers for cancer diagnosis and therapeutic response. In this study we characterized exosomes derived from different prostate cancer cells and explain the role of specific proteins present within exosomes which are involved in prostate cancer progression. Methods and Results: Exosomes were purified from the conditioned media(CM) from a panel of five prostate cancer cells and ‘normal’ RWPE-1 cells after 72 hours 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 detected the integrity of purified exosomes. Western blot analysis was also used to probe for different exosome markers including Actin, HSP70, HSP90, Rab5, CD9 and CD63. Our proteomic data shows that exosomes derived from specific prostate cancer cells present potential markers of prostate cancer progression. Conclusion: This study highlights a potential for differential protein composition of exosomes as a source of diagnostic biomarkers in addition to therapeutic targets for prostate cancer via non-invasive testing. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 440. doi:10.1158/1538-7445.AM2011-440