Reprogramming Antitumor Immunity: NK Cell Strategies to Navigate the Immunosuppressive Tumor Microenvironment

Tumor immune escape is a major barrier to durable cancer immunotherapy, as advanced malignancies create a tumor microenvironment (TME) that preferentially exhausts and disables T cell responses. While most approved cell therapies are T cell-based, this limitation motivates the exploration of an alternative effector cell platform. Natural killer (NK) cells, innate cytotoxic lymphocytes capable of antigen-independent recognition and killing, offer a compelling foundation for next-generation therapies with an improved safety profile. In this review, we first outline the cellular, molecular, and metabolic features of the immunosuppressive TME that restrict cytotoxic lymphocyte function, emphasizing mechanisms that limit immune cell-mediated responses. We then summarize key aspects of NK cell biology that can circumvent these barriers and critically evaluate current NK-based strategies, including engineered chimeric antigen receptor (CAR)-NK products and metabolic and trafficking interventions. Finally, we highlight emerging in vivo viral and mRNA/lipid nanoparticle platforms for CAR-NK generation and their potential to enhance scalability and therapeutic durability.