Recognition of a natural WT1 epitope by a modified WT1 peptide-specific T-cell receptor

摘要

Wilms' tumor gene WT1 is highly expressed in leukemia and in various types of solid tumors and exerts an oncogenic function. Thus, WT1 protein is a most promising tumor-associated antigen. We have been successfully performing WT1 vaccination with a 9-mer modified WT1235peptide, which has one amino acid substitution (M→Y) at position 2 of 9-mer natural WT1235 peptide (235-243 a.a.), for close to 700 HLA-A*24:02-positive patients with leukemia or solid tumors. Although vaccination of modified WT1 235 peptide induced natural WT1235 peptide-recognizing cytotoxic T-lymphocytes (CTLs) and exerted cytotoxic activity towards leukemia and solid tumor cells that expressed the natural WT1235 peptide (epitope) but not the vaccinated modified WT1235 peptide (epitope), the molecular basis has remained unclear. In this study, we established a modified WT1235 peptide-specific CTL clone, we isolated T-cell receptor (TCR) genes from it and transduced the TCR genes into CD8+ T-cells. The TCR-transduced CD8+ T-cells produced interferon-γ (IFNγ) and tumor necrosis factor-α(TNFα) in response to stimulation not only with the modified WT1235 peptide but also with the natural WT1235 peptide and lysed modified or natural WT1 235 peptide-pulsed target cells and endogenously WT1-expressing leukemia cells in a HLA-A*24:02-restriction manner. These results provided us, for the first time at molecular basis, with a proof-of-concept of modified WT1235 peptide-based immunotherapy for natural WT1235 peptide-expressing malignancies.