KLRK1 and cancer: Additional mechanisms that help cancers avoid NK cell recognition and killing, are selective downregulation of MHC-I alleles involved in T-cell recognition (such as HLA-A2) while sparing KIR inhibitory ligands such as HLA-C, and proteolytic shedding of NKG2D ligands MICA and MICB [270,271,272,273] whose cell surface expression normally leads to tumor killing via NKG2D engagement [202,203] (Figure 2B).