Tumor-associated antigens and Natural Killer cell receptor ligands (TAA/NKRL)

Tumor-associated antigens (TAAs) and Natural Killer (NK) cell receptor ligands are a broad class of molecules expressed on the surface of tumor cells that facilitate immune recognition and destruction. TAAs are proteins such as HER2 or CD20 that are either uniquely expressed or significantly overexpressed by malignant cells compared to normal tissues (National Cancer Institute, 2023). NK cell receptor ligands, including MICA, MICB, and ULBP family members, are stress-induced proteins that bind to activating receptors like NKG2D on NK cells, triggering a cytotoxic response (UniProt P43481; Shimasaki et al., 2020, Nature Reviews Drug Discovery). Conversely, some ligands like HLA-E interact with inhibitory receptors (e.g., NKG2A) to suppress NK cell activity, a mechanism often exploited by tumors for immune evasion (Kamiya et al., 2019, Blood Advances). Therapeutic interventions targeting these molecules include monoclonal antibodies, bispecific killer cell engagers (BiKEs), and CAR-NK cells, which are designed to either block inhibitory signals or potently activate NK cell-mediated lysis (Demaria et al., 2019, Nature Reviews Cancer). Challenges in targeting this group include the shedding of ligands into the systemic circulation, which acts as a decoy for the immune system, and potential on-target, off-tumor toxicities if the antigens are expressed on healthy cells.

Other names

Tumor-associated antigens (TAAs)NK cell ligandsTumor antigensStress-induced ligandsNKG2D ligandsMHC class I-related molecules

Drugs targeting these molecules primarily function by inducing antibody-dependent cellular cytotoxicity (ADCC), blocking inhibitory checkpoints (e.g., the NKG2A/HLA-E interaction), or directly engaging activating receptors on NK cells to promote tumor cell lysis (Demaria et al., 2019, Nature Reviews Cancer).