Peptide-based CAR-NK cells: A novel strategy for the treatment of solid tumors.

CAR-T cell therapy has been proven to be effective on hematological tumors, although graft-versus-host disease and cytokine release syndrome(CRS) limit its application to a certain extent. However, CAR-T therapy for solid tumors met challenges, among which the lack of tumor-specific antigens (TSA) and immunosuppressive tumor microenvironment (TME) are the most important factors. CAR-NK could be a good alternative to CAR-T in some ways since they can induce mild CRS and are independent of HLA-matching, but the efficacy of CAR-NKs remains limited in solid tumors. CAR cells armed with multiple tumor targeting molecules may obtain higher therapeutic efficacy against solid tumors. Due to large molecular weight, multivalent scFvs cannot be displayed efficiently on T cells and the high affinity of scFv to the target makes it easy to cause on-target, off-tumor(OTOT) toxicity. Peptides with low molecular weight and slightly lower affinity than scFvs allow immune cells to display multiple peptides to increase killing ability and reduce OTOT toxicity. In our study, peptide-based CAR-NK cells were designed to solve the dilemma of CAR-T in solid tumors. Firstly, the peptide-based CAR-NK92MI cells with A1 peptide were constructed and their inhibitory effects on the growth of A549 tumor cells were identified. Secondly, the tri-specific CAR-NK92MI cells with peptides that simultaneously targeted PD-L1, EGFR and VEGFR2 were developed for the combinatory therapy. Tri-specific CAR-NK92MI exhibited comparable killing activities to scFv-based CAR-NK92MI. Moreover, peptide-based CAR NK92MI mitigated OTOT toxicity. Our study implied that peptide-based CAR-NKs could behave as promising tools in solid tumor.