Tumor-specific peptide–Major Histocompatibility Complex class I (pMHC-I)

Tumor-specific peptide–Major Histocompatibility Complex class I (pMHC-I) complexes are the primary molecular signals used by the immune system to distinguish malignant cells from healthy tissue [3]. These complexes are formed when intracellular proteins, including mutated neoantigens or overexpressed tumor-associated antigens, are degraded by the proteasome into short peptides and loaded onto MHC class I molecules for presentation on the cell surface [3]. Recognition of these pMHC-I complexes by the T-cell receptor (TCR) on CD8+ cytotoxic T-lymphocytes triggers a signaling cascade that leads to the directed lysis of the tumor cell [3]. In the context of modern immunotherapy, these complexes serve as highly specific targets for engineered TCR-T cell therapies and bispecific molecules like Immune Mobilizing Monoclonal TCRs Against Cancer (ImmTACs) [4]. Unlike traditional antibody targets that are limited to surface proteins, pMHC-I targeting allows the immune system to "see" the internal proteome of the cancer cell [4]. However, therapeutic efficacy can be limited by the heterogeneity of peptide presentation, the requirement for specific patient HLA types, and the potential for "on-target, off-tumor" toxicity if the target peptide is present on essential healthy cells [1, 2]. Furthermore, tumors often employ immune escape mechanisms such as the downregulation of MHC-I expression to avoid detection by TCR-based therapies [3]. Despite these challenges, pMHC-I complexes remain a cornerstone of precision oncology due to their high specificity for tumor-derived mutations [1].

Other names

pMHC-IHLA-peptide complexNeoantigen-MHC complexTumor-associated antigen-MHC complexTS-pMHC

T-cell receptor (TCR) binding and redirection of T-cells to tumor cells, leading to MHC-restricted cytotoxic lysis.