NK cell activating receptor ligands (NK-ARLs)

Tumor-associated ligands recognized by NK cell activating receptors represent a diverse group of cell-surface proteins that are typically absent or lowly expressed on healthy cells but upregulated during cellular stress, malignant transformation, or viral infection [Duan et al., 2021]. These ligands include the MHC class I-related molecules MICA and MICB, the UL16-binding proteins (ULBP1-6), B7-H6, and the nectin-like protein CD155 (PVR) [Shimasaki et al., 2020]. They function as critical danger signals that bind to activating receptors on Natural Killer (NK) cells, such as NKG2D, NKp30, and DNAM-1, thereby triggering the release of cytotoxic granules and pro-inflammatory cytokines to eliminate the aberrant cells [Wu et al., 2017]. In many cancers, tumors employ immune evasion strategies such as the proteolytic shedding of these ligands by metalloproteinases like ADAM10 and ADAM17, which creates soluble decoys that neutralize NK cell receptors and impair anti-tumor immunity [Duan et al., 2021]. Therapeutic approaches targeting these ligands include monoclonal antibodies designed to block shedding, bispecific killer cell engagers (BiKEs) that bridge NK cells to tumor ligands, and chimeric antigen receptor (CAR)-NK cells engineered to recognize these stress-induced markers [Shimasaki et al., 2020]. While promising, these therapies face challenges such as potential on-target, off-tumor toxicity if ligands are expressed on healthy tissues under physiological stress and the immunosuppressive nature of the tumor microenvironment [Duan et al., 2021].

Other names

Tumor-associated ligands recognized by NK cell activating receptorsNKG2D ligandsStress-induced ligandsNK cell ligandsNatural killer cell activating ligands

Activation of NK cell-mediated cytotoxicity through binding of activating receptors (e.g., NKG2D, NKp30, DNAM-1) to their respective ligands on target cells, or therapeutic stabilization of these ligands to prevent immune evasion via proteolytic shedding.