Elevated interstitial fluid pressure promotes spheroid growth and reduces CAR-T therapeutic efficacy in solid tumors

Pancreatic ductal adenocarcinoma (PDAC) is among the deadliest solid tumors and is characterized by aggressive progression, a dense tumor microenvironment (TME), and resistance to conventional therapies. Among the barriers to effective treatments, the presence of elevated interstitial fluid pressure (IFP) may be important for drug penetration and immune cell infiltration. In this work, we present an innovative 3D microfluidic PDAC-on-a-chip that allows the application of IFP in a cell chamber to simulate the TME and evaluate the therapeutic efficacy of CAR-T cells engineered against the receptor EGFR expressed in tumor cells. Elevated IFP was associated with increased tumor spheroid growth, reduced caspase activation and decreased actin remodeling, indicating enhanced tumor resistance. CAR-T cells effectively targeted and eliminated tumor cells in 2D and 3D coculture models under normal pressure conditions. However, under high IFP, CAR-T-mediated cytotoxicity was impaired, indicating that some of the low efficacy of CAR-T cell therapy against solid tumors might be derived from IFP. These results highlight the importance of the mechanoenvironment in limiting the efficacy of current immunotherapies. Our model, which incorporates an IFP component, serves as a realistic preclinical platform for testing antitumor therapies in solid tumors. Statement of Significance In this work, we present an innovative 3D pancreatic tumor-on-a-chip model that incorporates interstitial fluid pressure (IFP), which is a key mechanical component of solid tumors. Using this platform, we discovered that IFP enhances tumor proliferation whilst diminishing immunotherapy efficacy. This indicates the important role of mechanical pressure in limiting immune cell function in solid tumors. Our model is a valuable preclinical platform for investigating the efficacy of anti-tumor therapies and supports the development of strategies to overcome mechanical resistance and enhance therapy efficacy in solid tumors, such as pancreatic cancer.