Fibroblast activation protein (FAP) and CD3 epsilon chain (CD3, specifically CD3E subunit) (FAP and CD3 (CD3E))

Fibroblast activation protein (FAP) is a type II transmembrane serine protease expressed at low levels in most adult tissues but highly upregulated in cancer-associated fibroblasts (CAFs) within the tumor microenvironment, as well as in sites of tissue remodeling such as fibrosis. FAP plays a crucial role in tissue remodeling, immune regulation, and tumor progression through its proteolytic activity and interaction with other cell-surface molecules. It serves as a promising target for cancer immunotherapies, especially those aiming to eliminate pro-tumorigenic stroma. CD3 refers to a multimeric protein complex (notably the epsilon subunit, CD3E), found on the surface of all T cells as part of the T-cell receptor (TCR) complex. CD3 is essential for T-cell activation and signal transduction upon antigen recognition. In therapy, bispecific modalities or CAR-T constructs are designed to target FAP on tumor stroma and CD3 on T cells, enabling localized T-cell activation and cytotoxicity toward the tumor.

Other names

FAPFAPαseprasefibroblast activation protein alphaCD3ET-cell surface glycoprotein CD3 epsilon chainT-cell receptor CD3 complex

FAP: Inhibition of enzymatic activity (blocking tumor-promoting fibroblast function); Targeted depletion of CAFs via immune cells; Direct cytotoxicity by CAR-T or bispecific antibody-recruited T cells. CD3: Activation of T cells through engagement with CD3, leading to immune synapse formation and cytotoxic response.