Inhibition of eEF-2K Enhances the Antitumor Efficacy of NK Cells

NK cells are increasingly being evaluated for their utility in cancer immunotherapy. However, their efficacy is often attenuated in the cancer microenvironment. The identification of additional checkpoint molecules that limit NK cell function is crucial to further development of NK cell-based therapies. In this study, we discovered eukaryotic elongation factor-2 kinase as an important participant in modulating the functional fate of NK cells. Dysfunctional NK cells from patients and tumor-bearing mice were found to have elevated EEF2K expression. CRISPR/Cas9-mediated EEF2K knockout promoted NK cell maturation, proliferation, and cytotoxicity and attenuated their exhaustion. Mechanistic studies demonstrated that EEF2K deletion activated Nrf2 in NK cells, thereby initiating cellular antioxidant signaling to sustain mitochondrial fitness and active metabolism, which was confirmed through combined proteomic high-throughput analysis and experimental observation. In particular, high levels of TGFβ in the tumor microenvironment were found to exacerbate oxidative stress and immunosuppression by inducing EEF2K. Therapeutically, systemic Eef2k deficiency effectively repressed melanoma metastasis and growth while modulating the intratumoral immune microenvironment, and adoptive therapy with EEF2K-knockout NK92 cells exhibited a significant antitumor effect and improved prognosis of human hepatocellular carcinoma xenografts in nude mice. Our findings reveal that eukaryotic elongation factor-2 kinase is an intracellular immune checkpoint of NK cells and provides a potential therapeutic target for developing NK cell-based cancer immunotherapies.