Natural killer group 2 member D ligands (NKG2DL) (NKG2DL)

Tumor cell surface stress ligands, primarily comprising the MHC class I polypeptide-related sequence A and B (MICA/B) and the UL16-binding protein (ULBP) family, are proteins upregulated in response to cellular stressors such as DNA damage, oxidative stress, and oncogenic transformation [Nature Reviews Cancer, 2008]. These ligands serve as critical 'induced-self' signals that are recognized by the NKG2D (Natural Killer Group 2 Member D) activating receptor, which is constitutively expressed on Natural Killer (NK) cells and certain T cell subsets [Frontiers in Immunology, 2019]. In the context of allogeneic NK cell therapy, these ligands are the primary targets for inducing potent anti-tumor cytotoxicity, as their expression is generally low or absent on healthy cells but high on many solid and hematologic malignancies [Journal of Hematology & Oncology, 2021]. However, tumors often evade this immune surveillance by using metalloproteinases to shed these ligands from the cell surface, creating soluble decoys (sMICA/B) that inhibit NK cell function and lead to receptor internalization [Science, 2018]. Therapeutic strategies currently in development include CAR-NK cells engineered with NKG2D receptors (e.g., NKX101) and monoclonal antibodies designed to stabilize surface expression or prevent shedding to restore immune recognition [Nkarta Therapeutics, 2023; Celyad Oncology, 2021].

Other names

MHC class I polypeptide-related sequence A (MICA)MHC class I polypeptide-related sequence B (MICB)UL16-binding proteins (ULBP1-6)Stress-induced ligandsTumor-associated stress ligandsRAET1 proteins

Binding and activation of the NKG2D (KLRK1) receptor on Natural Killer (NK) cells and cytotoxic T cells to trigger perforin and granzyme-mediated apoptosis of the target cell.