Engineering a HER2-CAR-NK cell secreting soluble programmed cell death protein with superior anti- tumor efficacy

Abstract To improve the therapeutic efficacy to relapse patient based-trastuzumab therapy, new therapy strategy was urgent to be explored. It is well known that HER2-specific chimeric antigen receptor (CAR) expressing NK cells is rapid development for solid tumor therapy with many advantages over HER2-CAR-T, and as an endogenous molecule, soluble PD-1 (sPD-1), a PD-1 extracellular domain, can block PD-1/PD-L1 pathway to promote cancer immunology. Herein, we engineered a new HER2-CAR-NK cells with co-expression of sPD-1 (sPD-1-CAR-NK cells), and assessed the cytotoxicity toward cancer cells, immunity activations and sPD-1 releases of sPD-1-CAR-NK cells in vitro and in both immunocompetent mouse model and humanized mouse model bearing HER2-high expression or trastuzumab-resistance-HER2 breast cancer. Furthermore, we compared with the anti-tumor effects of sPD-1-CAR-NK cells, HER2-CAR-NK cells and HER2-CAR-NK cells in combination with sPD-1. We demonstrated that HER2-CAR-NK cells specially diminished various HER2-expression breast cancer cells, and sPD-1-CAR-NK cells had ability to release bioactive sPD-1 and promote cytolysis activities of HER2-CAR-NK cells when incubated with target cells including trastuzumab-resistant cells. In vivo, sPD-1-CAR-NK cells had superior immunological anticancer efficacy than HER2-CAR-NK cells, and advantage over HER2-CAR-NK cells along with endogenous sPD-1. Together, these data indicate that HER2-specific CAR-NK cells carrying sPD1 show promise as a treatment for patients with HER2-positive breast cancer, and are is beneficial to develop for trastuzumab-resistance patient.