Tumor antigen-derived peptide-HLA class I complex (pHLA-I complex)

Tumor antigen-derived peptide-HLA class I complexes (pHLA-I) are the fundamental units of recognition for the adaptive cellular immune system in oncology. These complexes consist of a short peptide fragment, typically 8-11 amino acids in length, derived from intracellular proteins that have been processed by the proteasome and loaded onto HLA class I molecules in the endoplasmic reticulum (Rock et al., 2016, Nature Immunology). Once displayed on the cell surface, these complexes serve as flags that allow CD8+ T cells to identify and eliminate cells expressing mutated, fetal, or overexpressed proteins that are otherwise hidden within the cell. Therapeutic strategies targeting pHLA-I complexes include T-cell receptor (TCR) engineered T-cells and bispecific TCR-based engagers, which provide a way to target the vast intracellular proteome that is inaccessible to traditional antibody-based therapies (Nathan et al., 2021, NEJM). The clinical utility of these targets is highly dependent on the patient's specific HLA haplotype and the consistent presentation of the peptide by the tumor cells (D'Angelo et al., 2024, Lancet). However, challenges such as HLA loss as an immune escape mechanism and the potential for lethal cross-reactivity with similar peptides in healthy tissues remain significant hurdles in drug development (Hong et al., 2023, Cancer Discovery).

Other names

pMHC complexPeptide-MHC class I complexHLA-restricted tumor antigenTumor-associated antigen peptide-HLA complexPeptide-HLA complex

Recognition of the specific peptide-HLA complex by natural or engineered T-cell receptors (TCRs) or TCR-mimetic molecules, leading to the formation of an immunological synapse and subsequent T-cell mediated lysis of the target cell.