Non-viral approaches in CAR-NK cell engineering: connecting natural killer cell biology and gene delivery

Natural Killer (NK) cells are exciting candidates for cancer immunotherapy with potent innate cytotoxicity and distinct advantages over T cells for Chimeric Antigen Receptor (CAR) therapy. Concerns regarding the safety, cost, and scalability of viral vectors has ignited research into non-viral alternatives for gene delivery. This review comprehensively analyses recent advancements and challenges with non-viral genetic modification of NK cells for allogeneic CAR-NK therapies. Non-viral alternatives including electroporation and multifunctional nanoparticles are interrogated with respect to CAR expression and translational responses. Crucially, the link between NK cell biology and design of drug delivery technologies are made, which is essential for development of future non-viral approaches. This review provides valuable insights into the current state of non-viral CAR-NK cell engineering, aimed at realising the full potential of NK cell-based immunotherapies. Non-viral production of “off-the-shelf” CAR-NK cells. 1. NK cells may be purified from donor blood, differentiated from stem cells or produced from immortalised cell lines in the lab. 2. NK-specific CAR design modified from CAR-T designs to include NK transmembrane domains (NKG2D, NKp44), co-stimulatory receptors (e.g., DAP10, 2B4) and NK cell receptors (NKG2D). 3. Non-viral genetic modification of NK cells can include delivery of CAR construct via DNA or mRNA, and knock-in/out of specific genes using gene editing tools (e.g., CRISPR Cas9, transposons). This requires a gene delivery method which may include electroporation, lipid and multifunctional nanoparticles and cell penetrating peptides. The resultant CAR-NK cells are then expanded in vitro and may be delivered as an "off-the-shelf" product to treat multiple patients.