Tumor-associated antigen (TAA) presented on Major Histocompatibility Complex (MHC) (TAA-MHC)

Tumor-associated antigens (TAAs) presented on the Major Histocompatibility Complex (MHC) are short peptide fragments derived from intracellular proteins that are displayed on the cell surface for recognition by T-cells (Nature Reviews Cancer, 2021). These complexes are formed when proteins within the tumor cell are degraded by the proteasome and the resulting peptides are loaded onto MHC molecules (PubMed, PMID: 31048555). Unlike traditional antibody targets that require surface-expressed proteins, TAA-MHC complexes allow the immune system to detect the internal proteome of the cancer cell, including cancer-testis antigens like MAGE-A4 and NY-ESO-1 (Journal of Hematology & Oncology, 2023). Therapeutic strategies such as TCR-T cell therapies (e.g., Afamitresgene autoleucel) and bispecific T-cell engagers (e.g., Tebentafusp) are designed to recognize these specific peptide-MHC combinations with high affinity (FDA, 2024; NEJM, 2021). By binding specifically to these complexes, these agents can direct the cytotoxic activity of the immune system toward tumor cells while sparing healthy cells that lack the specific peptide-MHC combination. However, these therapies are restricted by the patient's HLA type, as the drug must match the specific MHC molecule presenting the antigen. Significant safety challenges include off-target toxicity if the target peptide sequence is similar to peptides found in vital organs, as seen in historical trials (Science Translational Medicine, 2013). Additionally, tumors may develop resistance through the downregulation of MHC molecules, a process known as immune escape. Successful clinical application requires precise patient stratification based on both HLA genotype and quantitative antigen expression levels.

Other names

Tumor-associated antigen-MHC complexpMHCPeptide-MHC complexCancer-testis antigen (CTA)Differentiation antigenOncofetal antigen

Recognition of peptide-MHC complexes by engineered or endogenous T-cell receptors (TCRs) or TCR-mimetic antibodies to induce targeted cell lysis and immune activation (Nature Reviews Drug Discovery, 2023).