NCR1 and breast cancer: They are also capable of reducing the activity of natural killer (NK) cells in several ways, e.g., by decreasing the expression of natural killer group 2, member D (NKG2D) ligands in glioblastoma and breast cancer [19,23]; by decreasing the expression of ligands for NK cell activating receptors such as NKp44, NKp30, NKp46, and CD16 [24,25]; or by increasing the expression of NK cell inhibitory receptor ligands [24,25].