KLRK1 and cancer: While in vitro studies and in vivo transplanted tumour models have shown that NK cells and activated CD8+T cells can effectively reject tumour transfectants expressing NKG2D ligands15, 16, 17, evidence for NKG2D function in long-term models that recapitulate the complexity of the tumour microenvironment in human cancer are scarce4, 18.