We investigated the cytotoxicity of the generated NK cells by co‐culturing three types of NK cells, iNK, PB‐NK, and CB‐NK cells, with K562 cells (chronic myeloid leukemia cell line) at a ratio of 1 : 1, respectively, followed by flow cytometry analysis for staining of CD56‐FITC, CD107a‐APC, and IFN‐γ‐PE. Here, IFNG is linked to chronic myelogenous leukemia, BCR-ABL1 positive.