KLRK1 and neoplasm: HDRT induces tumor cells to upregulate several cell surface molecules, including major histocompatibility complex (MHC) class 1 [9], the apoptosis-inducing death receptor FAS, and several natural killer group 2D (NKG2D) ligands, which enhance the recognition and cytolysis of the tumor by T-cells and NKs, respectively [47].