Senescent cells: Living or dying is a matter of NK cells

NK cells are lymphocytes of the innate immune system, which are able to deal promptly with stressed cells. Cellular senescence is a cell stress response leading to cell cycle arrest that plays a key role during tissue homeostasis and carcinogenesis. In this review, how senescent cells trigger an immune response and, in particular, the ability of NK cells to recognize and clear senescent cells are discussed. Special attention is given to the NK cell-mediated clearance of senescent tumor cells. NK cells kill senescent cells through a mechanism involving perforin- and granzyme-containing granule exocytosis, and produce IFN-gamma following senescent cell interaction, leading to hypothesize that NK cell-mediated immune clearance of senescent cells not only relies on direct killing but also on cytokine production, that in turn can promote macrophage activation. These aspects, as well as the ability of the senescence-associated secretory phenotype and senescent cell-produced extracellular vesicles to modulate NK cell effector functions, are described.