NK cell-based immunotherapy for cancer

Natural killer (NK) cells can induce an antigen-independent immune response against malignant cells. A growing number of scientific reports and clinical studies have shown promising anti-tumor effects when using NK cell based immunotherapy. Currently, various approaches are being used to enhance the number and function of NK cells. One approach uses cytokines to selectively boost both the number as well as the efficacy of anti-tumor functions of NK cells. Another emerging approach focuses on checkpoint inhibitors targeting the NK cell receptor. Furthermore, bi-specific and tri-specific engagers have been developed to enhance the specific immune response by cross-linking specific tumor antigens to effector cells. In addition, NK cell adoptive transfer therapies have shown promising prospects. Among the various sources of adoptive transfer NK cells, allogeneic haploidentical NK cells that have undergone short- or long-term activation or expansion have also demonstrated effective anti-tumor effects with a low rate of rejection and side effects. CAR-NKs, derived from a new type of genetic modification, show enhanced NK cell cytotoxicity, specificity, and targeting. These NK cell-based therapies have exhibited promising results in clinical trials with malignant tumors. In this review, the current progress on NK cell-based therapeutic approaches, NK cell manufacturing techniques and tumor therapy outcomes are discussed.