Electroporation of NKG2D RNA CAR Improves Vγ9Vδ2 T Cell Responses against Human Solid Tumor Xenografts

V gamma 9V delta 2 T cell-based anticancer immunotherapy has shown some promise in early-phase clinical trials but there is still large room for improvement. Using the extracellular domain of the human NKG2D, a stimulatory receptor expressed by V gamma 9V delta 2 T cells, we constructed NKG2D ligand-specific chimeric antigen receptors (CARs). We adopted a non-viral CAR approach via mRNA electroporation to modify V gamma 9V delta 2 T cells and demonstrated that, upon interaction with the NKG2D ligand-positive cancer cells, the CARs substantially enhanced the cytotoxic activity of the modified cells toward multiple cultured solid tumor cell lines, including those resistant to Zometa treatment. Repeated doses of the CAR-expressing cells resulted in tumor regression in mice with established tumors, extending median survival time by up to 132% as compared to the PBS control group. The findings suggest clinical potential for RNA CAR-modified V gamma 9V delta 2 T cells to treat a wide variety of NKG2D ligand-expressing cancers.