Abstract

Tumor hypoxia, a hallmark of the tumor microenvironment (TME), profoundly impacts the antitumor functionality of immune cells, particularly natural killer (NK) cells, which play a critical role in cancer immunosurveillance and immunotherapy success. This review provides a comprehensive analysis of the mechanisms by which hypoxia impairs NK cell-mediated cytotoxicity and antitumor activities, emphasizing the molecular pathways and cellular adaptations that enable cancer cell to evade NK cell attack. Key factors that participate in this phenomenon include the stabilization of hypoxia-inducible factors, metabolic reprogramming, angiogenesis, cancer stemness, autophagy, and the secretion of immunosuppressive molecules. Moreover, hypoxia induces phenotypic and functional changes in both cancer and NK cells, promoting tumor progression and resistance to immunotherapy. Emerging strategies to counteract hypoxia-induced immunosuppression are being explored, including nanotechnology-based approaches, cytokine-mediated NK cell preconditioning, and vascular normalization techniques. These interventions highlight promising avenues for enhancing NK cell functionality and synergizing with existing cancer therapies. By addressing the immunosuppressive challenges of the hypoxic TME, in this review, we underscore the potential of innovative strategies to improve therapeutic outcomes in cancer treatment. © The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature 2025.