Granzyme B degradation by autophagy decreases tumor cell susceptibility to natural killer-mediated lysis under hypoxia

Significance Natural killer (NK) cells are effectors of the antitumor immunity, able to kill cancer cells through the release of the cytotoxic protease granzyme B. NK-based therapies have recently emerged as promising anticancer strategies. It is well established that hypoxic microenvironment interferes with the function of antitumor immune cells and constitutes a major obstacle for cancer immunotherapies. We showed that breast cancer cells evade effective NK-mediated killing under hypoxia by activating autophagy that we have identified to be responsible for the degradation of NK-derived granzyme B. We demonstrated that blocking autophagy restored NK-mediated lysis in vitro, and facilitated breast tumor elimination by NK cells in mice. We provided evidence that targeting autophagy may pave the way to achieve more effective NK-based anticancer immunotherapy.