Tumor-associated antigen–Major Histocompatibility Complex (TAA-MHC)

Tumor-associated antigen–Major Histocompatibility Complex (TAA-MHC) complexes are molecular assemblies on the surface of melanoma cells that present intracellularly derived peptides to the immune system (Rock et al., 2016, Nature Reviews Immunology). These complexes consist of a peptide fragment from a tumor-associated antigen, such as gp100, MART-1, or MAGE-A4, bound within the groove of a Major Histocompatibility Complex (MHC) molecule, typically HLA-A*02:01 (Nathan et al., 2021, NEJM). In healthy cells, MHC molecules present self-peptides to maintain tolerance, but in melanoma, the presentation of mutated or overexpressed proteins allows the immune system to distinguish malignant cells from normal ones (Janeway's Immunobiology). These complexes serve as the primary recognition site for T-cell receptors (TCRs), making them critical targets for advanced immunotherapies including TCR-engineered T-cells (TCR-T) and bispecific T-cell engagers (Adaptimmune, 2024, FDA News Release). Drugs like Tebentafusp specifically bind to these complexes to redirect T-cells to lyse melanoma cells (Kimmtrak FDA Label). However, therapeutic efficacy can be limited by the downregulation of MHC molecules or the loss of antigen expression, which are common mechanisms of tumor immune evasion (Middleton et al., 2022, Clinical Cancer Research). Additionally, because these targets are HLA-restricted, treatment is often limited to patients with specific HLA genotypes, such as HLA-A*02:01.

Other names

Peptide-MHC complexpMHCHLA-peptide complexTumor-specific MHC-peptide complexMHC-restricted antigen

T-cell redirection and activation via T-cell receptor (TCR) mimicry or direct TCR binding to the peptide-MHC complex, leading to cytotoxic T-lymphocyte mediated lysis of the tumor cell (Nathan et al., 2021, NEJM).