KLRK1 and neoplasm: To explore whether the difference in sensitivity to NK cell-mediated killing of the cell lines A431 and HCT116 was related to differences in the expression of various ligands to NK cell activating (NKG2D, DNAM1) or inhibitory (KIR2D, NKG2A) receptors, expression levels of these ligands was assessed on both tumor cell lines (Supplementary Figure S2B).