Abstract A120: Disrupting PAR-1-mediated protease signaling in the PDAC tumor and its microenvironment

Abstract Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest malignancies, with a five-year survival rate of 13%. The desmoplastic tumor microenvironment (TME) that is characteristic of PDAC facilitates tumor growth and invasion and drug resistance. This dense TME is composed of extracellular matrix proteins and cancer-associated fibroblasts (CAFs) which directly contribute to tumor development. Modulating these components is a promising strategy to enhance the anti-tumor activities of existing drugs. As PDAC is a hypercoagulative disease, one component of interest is the coagulation system. To target this system without increasing bleeding risk, our group is investigating the specific roles of downstream signaling cascades including the protease-activated receptor 1 (PAR-1). Overproduction of tissue factor (TF) by PDAC cells promotes tumor growth, invasion, and metastasis through the PAR-1 signaling axis. Knockdown or knockout of PAR-1 in KPC2 cells dramatically reduced tumor growth in vivo and reduced the incidence and severity of lung metastases by a similar margin. These observations and the high expression of PAR-1 on PDAC cells posit PAR-1 as a viable therapeutic target for PDAC. The requirement of tumor cell PAR-1 for metastatic potential was investigated using the tail vein injection/experimental metastasis model. Time course analyses revealed that KPC2 control cells form high numbers of macroscopically evident pulmonary metastatic foci by 14 days post-injection whereas the number of pulmonary metastatic foci is significantly reduced with KPC2-PAR1KO cells. Injection of CFSE-labeled cells indicated PAR-1 is not required for the initial adherence or survival of metastatic tumor cells as the number of micrometastatic lesions were not different between KPC2 control and KPC2-PAR1KO cells 24 hours after injection. Metastasis experiments in NSG mice suggest tumor cell PAR-1 supports metastatic potential through mechanisms linked to and independent from evasion of anti-tumor immunity. Although the anti-tumor activity of immune cells within the PDAC microenvironment is limited, this compartment still offers significant promise for anti-cancer therapies. To potentiate the anti-tumor T cell response, chimeric antigen receptor T (CAR-T) cells targeting PAR-1, which is overexpressed on pancreatic tumor cells, were generated. Preliminary studies in vitro have demonstrated robust killing of PAR-1 expressing tumor cells. Additionally, single cell sequencing revealed that PAR-1 expression is significantly elevated in CAF populations within the TME, specifically myCAF subtype which shows significantly higher PAR-1 expression than iCAF (1. 36-fold). Understanding the crosstalk between malignant cells and other populations within the PDAC TME is critical for the development of therapies that target the coagulation system through the PAR-1 signaling axis. Investigating these targets will enhance our understanding of the cancer-relevant mechanisms of various components of the coagulation cascade in PDAC and facilitate clinical management of this disease. Citation Format: Jessica A. Occhiuto, Claire E. Reist, Jacqueline Peil, Malak Khalifeh, Huda Salman, Ateeq M. Khaliq, Ashiq Masood, Bumsoo Han, Matthew J. Flick, Melissa Fishel. Disrupting PAR-1-mediated protease signaling in the PDAC tumor and its microenvironment 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 (18Suppl₃): Abstract nr A120.