Harnessing Natural Killer Cell-Mediated Innate Immune Responses for Cancer Treatment: Advances and Challenges.

Natural killer (NK) cells are a gatekeeper of the body's innate defense system against cancers and infections. A growing body of literature from us and others finds that NK cells promote anti-cancer immune surveillance, and that defects in NK cell development are associated with poor clinical prognosis of cancers. In preclinical studies, NK cells were found to drive tumor regression and delay tumor relapse. Because NK cells are potentially less damaging to the body and are easier to develop than T cell-based therapies, efforts are being made to improve NK cell cytotoxicity and in vivo persistence for use as an adoptive, off-the-shelf immunotherapy. In this review, we discuss how tumor-intrinsic and -extrinsic factors suppress NK cells in the cancer microenvironment. We also outline current strategies that restore NK surveillance in cancer and challenges facing the clinical use of NK cell-based therapies.