Advancing NK Cell Therapies: Expansion and Activation for Next-Generation Immunotherapy

Abstract: Natural Killer (NK) cells, a subset of innate lymphoid cells, have emerged as a promising avenue in cancer immunotherapy due to their ability to recognize and eliminate malignant and virusinfected cells without prior antigen sensitization. Unlike T cells, NK cells function independently of Major Histocompatibility Complex (MHC) restriction, making them effective against tumors that evade adaptive immune responses. However, several challenges, including limited persistence, poor tumor infiltration, and immune suppression, hinder their clinical efficacy, particularly in solid tumors. Recent advancements in NK cell expansion, activation, and genetic engineering have significantly enhanced their therapeutic potential. Strategies such as cytokine-mediated stimulation, artificial scaffolds, and CRISPR-based modifications have improved NK cell persistence and cytotoxicity. Additionally, Chimeric Antigen Receptor (CAR)-modified NK cells offer targeted tumor recognition while minimizing the risk of Graft-Versus-Host Disease (GVHD) and Cytokine Release Syndrome (CRS), making them a safer alternative to CAR-T therapy. Despite these advancements, immunosuppressive tumor microenvironments and high manufacturing costs remain key obstacles. Emerging approaches, including metabolic reprogramming, synthetic biology, and combinatorial therapies integrating checkpoint inhibitors and bispecific antibodies, hold promise for overcoming these limitations. Furthermore, the development of off-the-shelf, induced Pluripotent Stem Cell (iPSC)-derived NK therapies is expected to enhance scalability and accessibility. This review highlights the latest progress in NK cell-based immunotherapy, addressing both current challenges and future directions in optimizing NK cell expansion, activation, and genetic engineering for clinical applications.