Clinical Applications of NK Cells in Tumor Immunotherapy

Natural killer(NK) cells,core components in human innate immunity,play a critical role in tumor cellular and antibody immunotherapy.NK cells can control tumor growth and metastasis through direct cellular cytotoxicity and secreted immune stimulatory cytokines.Multiple protocols currently aim to activate NK cells for utilization in cancer immunotherapy.Freshly isolated NK cells,transiently stimulated NK cells or lymphokine activated killer(LAK) cells are currently utilizated in autologous clinical trials.However,NK cells have displayed impaired functionality in cancer patients,which restricts their clinical effect.Several new protocols are available to improve clinical trial efficacy by increasing NK cells quantity and application of NK cells with high cytotoxicity.Large-scale production of clinical grade NK cells through long-term culture in vitro is one of the best ways in achieving these two goals.NK cells generated by certain methods with high quality and enough quantity have been translated into clinical use.The background of NK cells in immunotherapy,the status of NK cells in cancer patients,especially the new methods applied to expand cells in vitro are highlighted and discussed in this review.