Abstract A037: Unraveling the importance of pancreatic cancer extracellular signaling to endothelial cells within the tumor microenvironment
Authors: Finan Jennifer M. , Guo Yifei , MacPherson Kevin , Calvert Valerie , Pelz Carl , Petricoin Emanuel F. , Saugstad Julie A. , Sears Rosalie , Brody Jonathan R. 
Published: January 2024

Abstract
In many solid tumors, including pancreatic ductal adenocarcinoma (PDAC), the secretion of extracellular vesicles (EVs) has been shown to support tumor progression, chemotherapeutic resistance, and metastasis. Importantly, PDAC tumors are composed of up to 80% non-tumor cells and an extracellular matrix, yet no studies have been performed to determine whether PDAC EVs are preferentially imported by specific cells within the tumor microenvironment. Further, the RNA-binding protein HuR plays an important role in PDAC cells, supporting the stability and translation of transcripts that aid tumor cell stress responses. Our lab has recently found that EVs contain distinct mRNA and phosphorylated protein cargoes from donor cells. Further, HuR knockout (KO) cells produce EVs with significantly different mRNAs and phosphorylated proteins that EVs isolated from HuR wildtype (WT) cells. Considering the functional impact of EV cargoes on recipient cells, our study aims to identify the specific cell types in the tumor microenvironment that import PDAC EVs and investigate the role of PDAC cell HuR in this signaling process. We have generated human PDAC and mouse KrasG12D Trp53R172H driven (KPC) PDAC cell lines to express an EV reporter labeling the inner leaflet of cell membranes with GFP-nLuc. We utilized these cell lines in an immunocompetent mouse model of PDAC to determine which stromal cells import PDAC EVs in live mouse tumors. We found that endothelial cells have a significantly higher EV import than other stromal cells, and are now utilizing cyclic-immunofluorescence to confirm these findings and assess whether canonical endothelial cell tube formation proteins are increased with EV import. We will assess the functional importance of this signaling via single-cell RNA-sequencing of developed KPC EV reporter tumors. Future studies will interrogate the importance of HuR leveraging the EV reporter in KPC HuR WT vs. KO cells and through 3D endothelial cell tube formation assays treated with HuR WT vs. KO EVs. Collectively, our study sheds light on the preferential uptake of PDAC EVs by endothelial cells and highlights the potential role of tumor cell-intrinsic HuR in this signaling process. These findings expand our understanding of the interactions between PDAC and the tumor microenvironment, potentially paving the way for targeted therapeutic interventions in this devastating disease.
Citation Format: Jennifer M. Finan, Yifei Guo, Kevin MacPherson, Valerie Calvert, Carl Pelz, Emanuel F. Petricoin, Julie A. Saugstad, Rosalie Sears, Jonathan R. Brody. Unraveling the importance of pancreatic cancer extracellular signaling to endothelial cells within the tumor microenvironment [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Pancreatic Cancer; 2023 Sep 27-30; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84(2 Suppl):Abstract nr A037.