Abstract B037: Validation and translation of therapeutic potential of thrombin-PAR1 signaling in suppressing fibrosis using microphysiological PDAC tumor models

Abstract Pancreatic ductal adenocarcinoma (PDAC) creates complex tumor microenvironment (TME) hallmarked with a desmoplastic stroma that facilitates tumor growth/invasion, chemoresistance, and immunosuppression. It urgently needs the identification and evaluation of stromal components that can be targeted to reprogram the stroma to improve drug delivery and efficacy without making tumors more aggressive. Thus, we hypothesize that the coagulation system in the PDAC TME can be targeted to reprogram PDAC stroma to alleviate chemoresistance and drug delivery barriers. Specifically, the thrombin/protease-activated receptor 1 (PAR1) signaling axis can be targeted to suppress growth/invasion of pancreatic cancer cells (PCCs) and cancer associated fibroblast (CAF)-derived fibrosis. Our underlying rationale is based upon a leaky tumor vasculature in PDAC resulting in the release of circulating coagulation factors and subsequent activation of the coagulation system in the TME. Tissue factor expressed by PCCs initiates the conversion of prothrombin to the active serine protease thrombin, which then activates PAR1, whose signaling is thought to promote PCC growth/invasion and CAF-mediated fibrosis. We developed and employed novel microphysiological systems (MPS) of PDAC tumor-stroma, which were designed to reconstitute extravascular coagulation in the PDAC TME to specifically investigate the role of thrombin-PAR1 signaling events on PCC growth and CAF-mediated fibrosis. Our MPS was a microfluidic platform where PCC and CAF were co-cultured in the 3D extracellular matrix perfused with/without thrombin. In addition, PAR1 expression in murine and human PCCs and CAFs was genetically modified or pharmacologically inhibited. Our MPS enabled systematic and translational analyses on the therapeutic potential of blocking PAR1 signaling in PCCs, CAFs, or both. In murine MPS, genetic deletion of PAR1 drastically decreased thrombin-mediated PCC and CAF growth compared to that of MPS with wildtype cells. Human MPS with varying levels of PAR1 also suggest thrombin stimulates PCC-CAF crosstalk, including CAF growth, elevated expression of a-SMA and secreted collagen levels. Furthermore, pharmacological inhibition of PAR1 by vorapaxar decreases both PCC and CAFs in all human PCC/CAF pairs studied. Finally, we confirm the findings from our MPS using PDAC tumor-stroma xenograft models with both human PCC and CAF. A significant reduction in tumor size is observed with vorapaxar treatment, which attributes primarily to the reduction of CAFs. In summary, we validate and translate the therapeutic potential of thrombin-PAR1 signaling in reprogramming PDAC stroma using novel MPS of PDAC tumor-stroma model. Our study also demonstrates MPS as a promising system for target identification, validation, and streamlining preclinical studies for drug discovery. Citation Format: Sae Rome. Choi, Hye-ran Moon, Natalia Ospina Muñoz, Yun Chang, Xiaoping Bao, Bennett D. Elzey, Meliss L. Fishel, Matthew J. Flick, Bumsoo Han. Validation and translation of therapeutic potential of thrombin-PAR1 signaling in suppressing fibrosis using microphysiological PDAC tumor models [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research—Emerging Science Driving Transformative Solutions; Boston, MA; 2025 Sep 28-Oct 1; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2025;85(18_Suppl_3):Abstract nr B037.