ABSTRACT
Natural killer (NK) cells can discriminate between normal and cancer cells and are known to directly recognize and kill malignant cells or induce apoptosis. Thus, activation of NK cells is considered as a promising strategy for cancer treatment. However, clinical application has been somewhat limited because of difficulties in the preparation of sufficient number of highly cytotoxic/activated NK cells in vitro. We used cytokine stimulation to provide a suitable environment (activating receptor-ligand interactions) for the expansion of NK cells. This method potently expanded NK cells, and the final product was composed of highly proliferating NK cells. The expanded NK cells showed significant upregulation of various activation receptors such as CD69 and NKG2D. The latter is a particularly important receptor for triggering NK cell responses toward tumor cells.
