RESUMO
As the first line of defense of the host immune system, natural killer cells play important roles in anti-tumor immunity, either by direct anti-tumor effects, or by assisting T cell immune responses. However, NK cells are usually functionally exhausted in tumor microenvironment, accompanied with dysregulated expression of an array of surface receptors, restricting the effector potentials of NK cells. NK-based checkpoint immunotherapy aims to trigger anti-tumor efficacy by blocking NK cell surface inhibitory receptors, unleashing NK cells from inhibitory signals of the tumor microenvironment, and reversing NK cell exhaustion, representing a novel strategy in cancer therapy. With more in-depth research to reveal the mechanisms of action, indications, and biomarkers for specific NK cell checkpoint molecules, we shall fully exploit the potentials of NK-based checkpoint blockade immunotherapy.