Abstract LB-266: Large oncosomes reprogram prostate fibroblasts toward a pro-angiogenic phenotype

Abstract

Abstract Introduction: Cancer cells communicate with different cells in the tumor microenvironment, establishing a supportive stroma that sustains tumor development and facilitates the first steps of metastasis. Extracellular vesicles (EVs) have emerged as key functional mediators of this process. Aim of this study was to determine the mechanism of intercellular communication mediated by the atypically large EVs produced by highly migratory and metastatic tumor cells, referred to as large oncosomes (LO), and prostate fibroblasts (NAF). Methods: Filtration, differential centrifugation followed by iodixanol gradient; flow cytometry and confocal imaging; RNA-seq; kinase assay; TF array; luciferase assay; tube formation; siRNA; RT-qPCR. Results: Active AKT1 is significantly more expressed and functional in LO than in exosomes (Exo). Patients with metastatic disease express abundant active AKT1 in plasma LO. Uptake of LO harboring active AKT1 by NAF results in AKT1 and c-MYC activation. Conditioned media from LO-treated NAF, but not from Exo-treated NAF, promoted endothelial morphogenesis. The Dynamin (DNM) inhibitor Dynasore (Dyn) inhibited LO-uptake, as well as MYC activation and tube formation. Transient silencing of DNM2 significantly reduced LO uptake, suggesting that uptake occurs by phagocytosis. LO treatment increased levels of MYC targets in NAF, suggesting that MYC is involved in LO-induced reprogramming of NAF. Accordingly, MYC expression was higher in activated fibroblasts than NAF, and MYC overexpression in NAF induced hyperplasia in normal prostate epithelium in mice, suggesting MYC activation is an early event in cancer development. Summary/Conclusion: Our results indicate that tumor-derived LO induce a novel, c-MYC mediated, pro-tumorigenic reprogramming of fibroblasts that can be reverted by selectively inhibiting LO uptake. Support: National Institutes of Health NCI NIH R00 CA131472; NIH UCLA SPORE in Prostate Cancer award P50 CA092131; Avon Foundation Fund 02-2013-043 (to DDV). Citation Format: Valentina Minciacchi, Cristiana Spinelli, Mariana Reis-Sobreiro, Mandana Zandian, Rosalyn M. Adam, Edwin M. Posadas, Freeman R. Michael, Emanuele Cocucci, Neil Bhowmick, Dolores Di Vizio. Large oncosomes reprogram prostate fibroblasts toward a pro-angiogenic phenotype. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr LB-266.