PAX3-FOXO1 fusion protein-derived peptide-MHC complex (PAX3-FOXO1 pMHC)

The PAX3-FOXO1 fusion protein-derived peptide-MHC complex is a highly specific tumor neoantigen target found in alveolar rhabdomyosarcoma (ARMS). This target is generated by the chromosomal translocation t(2;13)(q35;q14), which fuses the PAX3 gene with the FOXO1 (formerly FKHR) gene, creating a chimeric transcription factor that drives the malignant phenotype. The unique amino acid sequence at the fusion breakpoint is processed into peptides and presented on the cell surface by Major Histocompatibility Complex (MHC) molecules, most commonly HLA-A*02:01. Because this sequence is entirely absent from the normal human proteome, it serves as an ideal target for precision immunotherapy, including TCR-engineered T-cell therapies and neoantigen vaccines. These therapeutic approaches aim to harness the cellular immune system to selectively destroy ARMS cells while sparing healthy tissues. However, the clinical utility of this target is limited by the requirement for patients to possess specific HLA alleles and the potential for tumors to evade detection by downregulating their antigen presentation machinery.

Other names

PAX3-FOXO1 neoantigenPAX3-FKHR fusion peptideAlveolar rhabdomyosarcoma fusion peptidePAX3-FOXO1 breakpoint peptide-HLA complex

T-cell receptor (TCR) mediated recognition of the fusion-derived peptide presented on MHC molecules, leading to cytotoxic T-lymphocyte activation and selective lysis of tumor cells expressing the PAX3-FOXO1 translocation.