Abstract 4599: Blood and lymphatic endothelial cell contractility-mediated vessel permeability regulates interstitial fluid pressure and T cell infiltration in the tumor microenvironment
Authors: Peng Yansong , Lee Esak 
Published: June 2023

Abstract
Solid tumors such as breast and pancreatic cancer are characterized by poor prognostic outcomes with high interstitial fluid pressure (IFP), which promotes tumor progression by modulating angiogenesis, matrix metalloproteinase activity, and cancer cell motility and compromises immunotherapies by keeping immune cells (e.g., T cells) from infiltrating into the tumor. To reduce tumor IFP, researchers tried to decrease solid stress and normalize hyperpermeable blood vessels (BV) in tumors, but how lymphatic vessels (LV) are impaired in the tumor microenvironment is poorly understood. Several studies reported that vascular endothelial growth factor C (VEGFC) treatment defeated tumors by promoting lymphangiogenesis and boosting T cell recruitment, while it has also been recognized to promote lymph node metastasis. Given the controversial roles of VEGFC, the main goals of this study are to control LV permeability and promote drainage by identifying currently unappreciated roles of rho-associated protein kinase 1 and 2 (ROCK1/2) in regulating lymphatic endothelial cell (LEC) contractility, junctions, and drainage in tumors. We will have blood endothelial cells (BEC) as controls to understand how ROCK1/2 and cell contractility affect LEC/BEC junctions and permeability differently. Here, we created a three-dimensional (3D) bioengineered model of vascularized pancreatic and breast tumors to study vessel junctions, permeability, and IFP formation. The device consisted of a LEC or BEC lined, perfusable channel and a tumor-filled ECM chamber. We observed impaired barrier function of tumor BV/LV with increased permeability and loss of tight junctions compared to healthy vessels. To quantify the contractility of LEC/BEC, we employed traction force microscopy (TFM) by creating a 2D biomimicry of the endothelial monolayers using micropatterned polyacrylamide gel substrates with tunable stiffness. Using TFM, we showed that the combination of tumor-secreted factors and elevated matrix stiffness increased the traction of LEC/BEC, resulting in their loss of tight junctions. Using Rho kinase blockade to inhibit ROCK1/2 reduced the contractility of endothelial cells, reconstructed vessel structural integrity and functionality, and reduced intratumoral IFP in animal models. We expect that a decrease in the tumor IFP due to the restoration of lymphatic drainage would increase T cell infiltration, suppress tumor growth, and improve the survival of tumor-bearing mice combined with the anti-PD-1 or anti-PD-L1 therapy in our future studies. Together, our study provides new insights into understanding the physical interaction of endothelial, tumor, and immune cells, evidence of rho-kinases as a target for cancer immunotherapy, as well as a promising way to increase the efficacy of immunotherapies in cancer patients.
Citation Format: Yansong Peng, Esak Lee. Blood and lymphatic endothelial cell contractility-mediated vessel permeability regulates interstitial fluid pressure and T cell infiltration in the tumor microenvironment. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4599.