Natural Killer Cells: Prospects in Cancer Immunotherapy

In cancer immunotherapy, Natural Killer (NK) cells have achieved prominence. NK cells were identified in the 1970s as a subgroup of lymphocytes containing larger cytoplasmic granules. These cells are widely distributed in all lymphoid and non-lymphoid tissues, including bone marrow, lymph nodes, the spleen, peripheral blood, the lungs and liver. Because they do not present gene rearrangements during their ontogeny, they constitute a lineage of innate lymphoid cells. Immunotherapy in cancer has been reported with the use of Interleukin (IL) for the NK cell induction in clinical trials, which are discussed in this review. IL-treated NK cells directly kill target tumor cells through at least four mechanisms, the release of cytoplasmic granules, death receptor-induced apoptosis, production of effector molecules, or antibody-dependent cytotoxicity. More recently, Chimeric Antigen Receptor (CAR) gene transfer to primary NK cells or the human NK-92 cell line has been used to introduce new therapeutic options. The genetic manipulation of NK cells objected to the expression of CARs, allowing them to recognize tumor-specific antigens associated with increased survival, proliferation and cytotoxicity. Although there are advances in cancer immunotherapy, new therapies targeting tumor cells are required, as well as NK cell survival in tumor microenvironments, increase in their antitumor activity and immunosuppressive T cells control.