Natural killer (NK) cells and their involvement in different types of cancer. Current status of clinical research

Natural killer cells are the main agents of innate immunity. Since 1970, various studies have repeatedly confirmed their involvement in decreasing local tumor growth and also decreasing the risk of metastasis, due to their cytotoxic effects and also through the release of immunostimulatory cytokines such as IFN-gamma. In the 1990s, several studies demonstrated the existence of certain inhibiting and stimulating receptors of these cells, leading to the concept of “induced self”, thus explaining why tumors with MHC-1 are destroyed and autologous cells without it are saved out. Recognition and destruction of tumor cells by the NK cells are the result of complex interactions between inhibiting and activating factors. This paper, based on extensive research of currently available studies, summarizes the mechanisms employed by the NK cells to destroy the cancer cells, thus highlighting their role in the risk of tumor recurrence as well as their use and handling in certain types of immunotherap