Overcoming barriers in CAR-NK immunotherapy: CRISPR-Driven advances in checkpoint editing and allogeneic design.

Chimeric antigen receptor (CAR)-engineered natural killer (NK) cells are emerging as an exciting avenue in cancer immunotherapy due to their potent cytotoxicity to malignant cells and lower risk of graft-versus-host disease (GvHD) than conventional T cell therapies. The new technology of CRISPR/Cas9 genome editing has significantly expedited the engineering of CAR-NK cells by enabling easy, multiplex, and precise changes to enhance their efficacy, persistence, and specificity to tumors. This review focuses on the incorporation of CRISPR technology into CAR-NK cell development. It examines uses of knockout of inhibitory checkpoint genes (CISH, PD-1, and TGFBR2), as well as knock-in of CAR into safe genomic locations and multiplex editing of CAR-NK cells to improve cytotoxicity against cancer while resisting suppression from the tumor microenvironment (TME). We further explore immuno-cytokine armoring strategies by knock-in of IL-15 or IL-12, to ensure prolonged proliferation and survival of NK cells, and investigate CRISPR-mediated knockouts of immune inhibitors like NKG2A and TIGIT, to evade immune strategies used by the tumor to evade immune destruction. Furthermore, CRISPR-mediated upregulation of the homing receptor enhances NK cell tumor infiltration, addressing a major obstacle in treating solid tumors. It is significant to mention the progress in generating off-the-shelf products, which is a key step supporting the pursuit of allogeneic therapies. While substantial progress has been made, challenges remain related to optimizing CRISPR delivery, off-target effects, and enhancing in vivo persistence. Future directions of CAR-NK studies will likely capitalize on next-generation genome editing tools and synthetic biology for the development of tunable and logic-gated CAR-NK cells. Overall, this review illustrates the revolutionary capacity of combining CRISPR technology with CAR-NK immunotherapy to develop next-generation programmable and efficacious treatments for hematologic and solid malignancies.