To characterize the functional consequence of reduced NKG2D expression, we co-cultured NKL cells with the tumor cell line K562 for 2 h and then measured cell surface expression of lysosomal-associated membrane protein 1 (LAMP-1) on NKL cells as a marker for cytotoxic degranulation, indicating the cytotoxic reactivity of NK cells toward tumor cells (54). This evidence concerns the gene KLRK1 and neoplasm.