Natural killer cells control metastasis via structural editing of primary tumors in mice

Natural killer (NK) cells are innate immune lymphocytes which express an array of activating and inhibitory receptors. These receptors bind a large spectrum of ligands, which are expressed on stressed, malignantly transformed or virally infected cells, as well as on bacterial, fungal, and parasitic pathogens. The decision on whether or not to kill the target is based on the integration of activating and inhibitory signals sent downstream from NK cell receptors. One of the most prominent NK cell activating receptor families is the family of natural cytotoxicity receptors (NCRs) which includes NKp30, NKp44, and NKp46. NKp46 is the only NCR to have a fully functional mouse orthologue denoted Ncr1. Despite a large body of evidence highlighting its importance in the clearance of both solid and liquid tumors, the membrane-bound tumor ligand for NKp46 and its mouse orthologue Ncr1 is still unknown. Here we review the discovery of a novel role for NKp46/Ncr1, not only in tumor clearance but also in prevention of metastasis by structural editing of primary tumors.