KLRK1 and lung cancer: Compared to mock-transduced NK-92 cells, NKG2D CAR-NK92 cells displayed significantly higher cytolytic activity, while NKG2D-IL-21 CAR-NK-92 cells showed the highest cytolytic activity against NKG2DL (+) lung cancer cells, but there were not significant differences when co-cultured with the NKG2DL (−) lung cancer cells (Fig. 3A).