FAP and cancer: The mechanisms of CAR-T cell resistance are multifaceted, with one major obstacle being the extracellular matrix (ECM) barriers (18) mainly derived from cancer-associated fibroblasts (CAFs), which highly express fibroblast activation protein (FAP) to impede infiltrating of T cells, thereby shaping an immune-suppressive tumor microenvironment, especially in virus-related HCC (19–21).