Purpose Programmed cell death 1 (PD-1), which is upregulated under the continuous induction of the tumor microenvironment, causes chimeric antigen receptor (CAR)-T cell hypofunction via interaction with programmed death ligand 1 (PD-L1). This study aimed to construct CAR-T cells that are resistant to PD-1 inhibition to improve the effect of CAR-T cells in solid tumors. Methods We constructed a type of dual-function CAR-T cell that targets tumor-associated antigen c-Met and blocks the binding of PD-1 with PD-L1. The expression of c-Met, PD-L1, and inhibitory receptors was measured using flow cytometry. The cytotoxicity, cytokine release, and differentiation level of CAR-T cells were determined using lactate dehydrogenase release assay, enzyme-linked immunosorbent assay, and flow cytometry, respectively. The levels of p-Akt, p-MAPK, caspase-3, and Bcl2 were detected by western blot. The in vivo anti-tumor effect was evaluated using tumor xenograft models. Results Dual-function CAR-T cells could mediate enhanced active signals upon encountering target antigens and had targeted cytotoxicity to target cells. However, the cytotoxicity of c-Met-CAR-PD-1+ T cells was impaired due to the interaction of PD-1 with PD-L1. By blocking the binding of PD-1 and PD-L1, the novel dual-function CAR-PD-1+ T cells could maintain cytotoxicity to PD-L1+ tumor cells. In tumor tissue, the dual-function CAR-T cells showed lower inhibitory receptor expression and lower differentiation characteristics, which resulted in potent anti-tumor effects and prolonged survival in PD-L1+ tumor xenograft models compared to single-target CAR-T cells. Conclusion These results confirm that the novel dual-function CAR-T cells exhibit stronger anti-tumor activity against solid tumors than traditional single-target CAR-T cells and present a new approach that enhance the activity of CAR-T cells in solid tumors.
Keywords: C-Met; Cancer immunotherapy; Chimeric antigen receptor; PD-1; Tumor microenvironment.