Tumor-associated ligands recognized by NK activating and inhibitory receptors (NK cell ligands)

Tumor-associated ligands recognized by NK activating and inhibitory receptors comprise a diverse set of molecules that regulate the activity of Natural Killer (NK) cells within the tumor microenvironment. Activating ligands, such as MICA, MICB, and the ULBP family, are often upregulated in response to cellular stress and DNA damage, binding to the NKG2D receptor to trigger tumor cell lysis (PMID: 29461216). Conversely, inhibitory ligands like HLA-E and classical MHC class I molecules engage receptors such as NKG2A and KIRs to deliver 'off' signals, allowing tumors to evade immune detection (PMID: 30504761). Therapeutic strategies targeting these interactions include monoclonal antibodies that block inhibitory checkpoints or bispecific engagers that recruit NK cells to ligand-expressing tumor cells. A significant challenge in targeting these ligands is their susceptibility to proteolytic shedding, which produces soluble forms that can neutralize therapeutic agents and systemically suppress NK cell function (PMID: 31104230). Monitoring the expression levels of these ligands on the cell surface versus their soluble counterparts is essential for predicting patient response to NK-based immunotherapies. Overall, this class of molecules represents a critical interface in the immune-oncology landscape, balancing the activation and inhibition of innate immune surveillance.

Other names

NK cell ligandsNKR ligandsTumor-expressed NK ligandsNatural killer cell receptor ligandsStress-induced ligands

Competitive inhibition of inhibitory receptors, activation of NK cells via activating receptor engagement, and antibody-dependent cellular cytotoxicity (ADCC).