In flow cytometric and Western blot analyses, we found the NKG2D level in NK cells was also decreased upon incubation with cisplatin-resistant lung cancer cells, suggesting that the reduction of both the NKG2D ligand level in tumor cells and the NKG2D level in NK cells will lead to the reduced NKG2D ligand/NKG2D interaction, which may result in developing the immune escape of cisplatin-resistant lung cancer cells from the NK cell action. This evidence concerns the gene KLRK1 and neoplasm.