Shared tumor-specific epitope–HLA Class II complex (pHLA-II complex)

The Shared tumor-specific epitope–HLA Class II complex is a molecular assembly consisting of a tumor-derived peptide (epitope) bound to a Major Histocompatibility Complex (MHC) Class II molecule. Unlike private neoantigens, these epitopes are "shared" or "public," meaning they are derived from common oncogenic mutations (e.g., KRAS G12D) or overexpressed proteins (e.g., Cancer-Testis antigens like MAGE-A3 or NY-ESO-1) found across multiple patients (2.1.4, 3.2.1). While MHC Class II is traditionally expressed on professional antigen-presenting cells to activate CD4+ T cells, its expression on tumor cells—often induced by the Class II transactivator (CIITA) or IFN-gamma—allows for direct recognition by the immune system (2.2.1, 2.2.4). This complex serves as a critical target for advanced immunotherapies, including TCR-engineered T cells (TCR-T) and TCR-mimetic antibodies, which aim to bypass the limitations of traditional CAR-T cells by targeting intracellular proteins (2.3.2, 3.4.1). Therapeutic success depends on the precise matching of the patient's HLA allele (e.g., HLA-DP4) and the presence of the specific tumor antigen (3.1.3, 3.1.4).

Other names

Shared tumor antigen-MHC II complexPublic neoantigen-HLA II complexTumor-specific MHC II complextsMHC-IIPeptide-HLA Class II complexMHC Class II-restricted tumor antigen complex

Recognition of the peptide-HLA complex by engineered T-cell receptors (TCRs) or TCR-mimetic antibodies, leading to the activation of cytotoxic or helper T-cell responses against tumor cells.