Abstract 4322: Exosomal delivery of stroma-derived miR-145 inhibits pancreatic cancer cell proliferation

Abstract We previously reported that within the pancreatic ductal adenocarcinoma (PDAC) microenvironment, miR-145 and miR-199a are exclusively expressed in tumor-associated stroma (TAS) cells, but these miRNAs are present in PDAC cells following co-culture with TAS cells. We hypothesized that miRNAs function as paracrine signals via exosomal exchange between TAS cells and adjacent PDAC cells. Primary cultures of human TAS and PDAC cells were employed. Membrane-bound microparticles were isolated from TAS conditioned, serum-free culture media by sequential ultracentrifugation followed by ultrafiltration. Exosomes and microvesicles were then assayed for particle size distribution using nanoparticle tracking analysis and electronic microscopy. miRNA expression levels were determined using quantitative PCR. miRNA transfection was performed with RNAiMax reagents. Cell viability was measured by Alamar Blue. Statistics were performed using Prism 6 software. Following transfection of human TAS cells with cel-miR-39, a nonhuman miRNA, we demonstrated that miRNA exchanges occurred between TAS cells and neighboring PDAC cells via a process that is not dependent upon cell-cell contact. We next confirmed the presence and enrichment of miR-145-5p in TAS-cell-derived exosomes (8-fold higher concentrations in exosomes than parental cells, p<0.05). Feeding of TAS-derived exosomes or transfection of miR-145-5p mimics into PDAC cells led to dose-dependent decreases in PDAC cell viability (p<0.05). Taken together, our data suggest that stroma derived exosomes deliver miRNAs to adjacent PDAC cells and may function as tumor-suppressing paracrine signals in the case of miR-145. This finding provides a potential explanation for the observation that stroma depletion paradoxically accelerates PDAC progression in murine models. Citation Format: Song Han, Sayali Belsare, DongYu Zhang, Mark Beveridge, Carlos Rinaldi, Jose G. Trevino, Thomas D. Schmittgen, Steven J. Hughes. Exosomal delivery of stroma-derived miR-145 inhibits pancreatic cancer cell proliferation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4322. doi:10.1158/1538-7445.AM2017-4322