The two-faces of NK cells in oncolytic virotherapy.

Oncolytic viruses (OVs) are immunotherapeutics capable of directly killing cancer cells and with potent immunostimulatory properties. OVs exert their antitumor effect, at least partially, by activating the antitumor immune response, of which NK cells are an important component. However, if on the one hand increasing evidence revealed that NK cells are important mediators of oncolytic virotherapy, on the other hand, NK cells have evolved to fight viral infections, and therefore they can have a detrimental effect for the efficacy of OVs. In this review, we will discuss the dichotomy between the antitumor and antiviral functions of NK cells related to oncolytic virotherapy. We will also review NK cell-based and OV-based therapies, engineered OVs aimed at enhancing immune stimulation, and combination therapies involving OVs and NK cells currently used in cancer immunotherapy.