LAUSR

Introduction: Pancreatic ductal adenocarcinoma (PDAC) is a fatal disease associated with a 5-year survival rate of ~9%. The most notable clinical features of PDAC are its propensity for aggressive invasion, metastasis (mainly to the liver) and an inherent resistance to conventional therapies. A better understanding of the biology of PDAC metastasis is critical to improving the clinical management of this disease. PDAC is characterized by a dense desmoplastic reaction with up to 50% of the tumor mass consisting of stroma. The major cellular component of the PDAC stroma is the activated pancreatic stellate cell (aPSC). These cells contribute to PDAC progression through extracellular matrix deposition and the secretion of soluble factors. The objective of this study was to determine whether the aPSCs also play a role in PDAC metastasis by contributing to a pro-metastatic microenvironment in the liver. Methods: We used a syngeneic cell line, LMP-derived from the KPC PDAC mouse model-that recapitulates the clinical course of the disease. When implanted in the pancreas, LMP cells grow rapidly and metastasize aggressively to the liver, and this is associated with PSC activation and expansion. We investigated the ability of PSC and aPSC-derived exosomes to activate hepatic stellate cells (HSC) using a co-culture system in vitro and analyzed the effect of aPSC-derived exosomes on LMP liver metastasis in vivo. Moreover, the protein cargo of PSC-derived exosomes was analyzed by mass spectrometry, in order to identify molecular mediators of PSC-HSC communication that can promote liver colonization by disseminating PDAC cells. Results: In mice orthotopically implanted with LMP cells, we observed a rapid activation of HSC, an event that preceded tumor cell entry into the liver, as assessed by confocal microscopy and PCR. Similarly, the injection of aPSC-derived exosomes into tumor-naive mice resulted in a liver stromal response, involving HSC and liver-associated fibroblasts. Cultured HSC could be activated by co-culture with aPSCs or by uptake of aPSC-derived exosomes. Moreover, in mice injected with aPSC-derived exosomes, spontaneous liver metastasis was accelerated, resulting in increased metastatic burden. Mass spectometry identified several potential mediators of HSC activation in the aPSC-derived exosomes, including the IGF-2 mRNA binding protein-1 (IMP-1)-an oncofetal, RNA-binding protein involved in the regulation of cytoplasmic mRNA-fate. Finally, IMP-1 silencing in aPSCs reduced HSC activation and the pro-metastatic effect of aPSC-derived exosomes. Conclusions: Our data identify a novel PSC-HSC crosstalk mechanism that contributes to generating a pro-metastatic microenvironment in the liver and implicate aPSC-derived exosomal IMP-1 in this inter-cellular communication. Our results identify IMP-1 as a potential target for curtailing the metastatic spread of PDAC. Citation Format: John David Konda, Masakazu Hashimoto, Jian Zhang, Maria Celia Fernandez, Ni Wang, Stephanie Perrino, Laura Montermini, Janusz Rak, Jean-Sebastien Pelletier, Andrew M. Lowy, Pnina Brodt. Pancreatic ductal adenocarcinoma associated stellate cells promote a pro-metastatic microenvironment in the liver [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5076.