Natural killer (NK) cells have been known to enhance the host immune responses against cancer. NK cell number and cytotoxicity in patients with cancer is often low. Therefore, we developed a large-scale ex vivo NK cell expansion method without feeder layers and introduced NK cell-based autologous immune enhancement therapy (AIET). In this paper, we discuss the epidemiological data that show the relationship between NK activity and cancer incidence, monitoring of NK cell number and activity, anti-cancer activities of NK cells in vitro and in vivo and the effects of the combination of expanded NK cells with monoclonal antibody drugs on cancers through antibody-dependent cellular cytotoxicity. Finally, we also present the clinical cases of NK cell-based AIET and the effect of AIET on advanced stage of pancreatic cancer and on various advanced cancers refractory to conventional therapies. NK cell-based AIET might be a useful strategy in the multidisciplinary approach to cancer.
Keywords: NK cell; antibody-dependent cellular cytotoxicity (ADCC); immunotherapy; palliative therapy; pancreatic cancer.