Verhoeven et al. observed that Ewing sarcoma cell lines and primary Ewing sarcoma tumor cells expressed ligands for the activatory NK cell receptors NKG2D and DNAM-1, and that the NK cell cytotoxicity to Ewing sarcoma cells critically depended on the combination of NKG2D and DNAM-1 signaling, [93]. This evidence concerns the gene KLRK1 and Ewing sarcoma.