Fig. 4

General strategies that improve the therapeutic safety of engineering dCAR-T cells. a In the presence of the first tumor antigen (e.g., CEA) >and the second tumor antigen (e.g., MSLN), the intracellular CD3ζ and 4/1BB signal domain were phosphorylated, resulting in the fact that cognate tumor cells expressing MSLN and CEA are required for dCAR-T cell activity. b For tumor cells expressing a single tumor-associated antigen, dCAR-T cells have low-level activation in the presence of CEA yet no activation in the presence of MSLN, resulting in tumor survival and recurrence. For dual antigen-expressing tumor cells, dCAR-T cells have high-level activation and exert significant cytotoxicity, resulting in tumor apoptosis. c To achieve the accurate control of dCAR-T cells in vitro and in vivo, the CD3ζ signaling pathway of dCAR structure was regulated by an exogenous molecular. Therefore, switchable dCAR-T cells eliminate cognate tumor cells expressing the tumor antigens specific for the second CAR of this model only in the presence of the switch molecule. d To decrease normal tissue damage, a cleavable masking peptide could be re-engineered into the N-terminal of CEA-CD3ζ pathway domain, thereby blocking the antigen recognition domain of the CEA scFv. Thus, masked dCAR-T cells eradicate cognate tumor cells only in the presence of the tumor-associated protease locally active in tumor environment, thus enabling dCAR-T cell to differentiate tumor tissue and normal tissue