Abstract 357: Exosome-mediated transfer of alphaV integrins promotes prostate cancer cell-cell communication

Abstract Intercellular communications have been recently shown to be mediated by exosomes, exocytosed vesicles of endosomal origin, which are thought to be involved in cancer progression. We have investigated whether integrins, transmembrane receptors that are known to be deregulated in cancer progression, are transferred among different subsets of prostate cancer cells through exosomes and have the ability to support functional aberrations in the recipient cells. Recent studies have characterized integrin expression in exosomes but have not investigated whether integrins are actually shuttled to recipient cells and whether they modulate the phenotype of these cells. We have focused on the alphaVbeta3 and alphaVbeta6 integrins since they are highly up-regulated in cancer and metastasis. We show here that these alphaV integrins are present in exosomes of several prostate cancer cells and are transferred from donor to recipient cells. The quality of our exosome preparations was tested by electron microscopy, which confirms the size range (40-100 nm) and the typical cup shape of these vesicles; by continuous sucrose gradient, which shows a density range of 1.15-1.17g/ml characteristic of exosomes, and by biochemical characterization using antibodies to CD63 and CD81. After exosome internalization was determined by confocal microscopy of red PKH26-labeled exosomes followed by Z-stack image analysis, these integrins are shown to be transferred as proteins to recipient cells by immunoblotting. Furthermore, FACS analysis demonstrated that these integrins are localized to the cell surface indicating they are functional. The active state of alphaVbeta6 was confirmed in cell migration assays which show that the alphaVbeta6 integrin transferred through exosomes mediates cell migration of recipient cells on an alphaVbeta6 specific ligand, latency-associated peptide-TGFBeta. To evaluate the relevance of our findings, we purified exosomes from sera of TRAMP mice which had developed prostate cancer. The results show that the alphaVbeta3 integrin is expressed in these exosomes and is a potential biomarker for prostate cancer diagnostic purposes. Overall, this study shows that alphaV integrins are transferred through exosomes to recipient cells and promote cell migration on specific ligands, thus, suggesting that this novel pathway may lead to increased prostate cancer metastasis in distinct distant sites. Supported by NIH-CA089720 and P01CA140043 to LRL; an American-Italian Cancer Foundation Post-Doctoral Research Fellowship to CF; a JGSBS Alumni Association Graduate Student Travel Fellowship to AS. Citation Format: Amrita Singh, Carmine Fedele, Renato V. Iozzo, Lucia R. Languino. Exosome-mediated transfer of alphaV integrins promotes prostate cancer cell-cell communication. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 357. doi:10.1158/1538-7445.AM2015-357