Specific recognition and inhibition of Ewing tumour growth by antigen-specific allo-restricted cytotoxic T cells

BACKGROUND: The development of a successful immunotherapy is hampered by an ineffective T-cell repertoire against tumour antigens and the inability of the patient's immune system to overcome tolerance-inducing mechanisms. Here, we test the specific recognition and lytical potential of allo-restricted CD8(+) T cells against Ewing tumour (ET) associated antigens Enhancer of Zeste, Drosophila Homolog 2 (EZH2), and Chondromodulin-I (CHM1) identified through previous microarray analysis. METHODS: Following repetitive CHM1(319) (VIMPCSWWV) and EZH2(666) (YMCSFLFNL) peptide-driven stimulations with HLA-A(*)0201(+) dendritic cells (DC), allo-restricted HLA-A(*)0201(−) CD8(+) T cells were stained with HLA-A(*)0201/peptide multimers, sorted and expanded by limiting dilution. RESULTS: Expanded T cells specifically recognised peptide-pulsed target cells or antigen-transfected cells in the context of HLA-A(*)0201 and killed HLA-A(*)0201(+) ET lines expressing the antigen while HLA-A(*)0201(–) ET lines were not affected. Furthermore, adoptively transferred T cells caused significant ET growth delay in Rag2(−/−)γ(C)(−/−) mice. Within this context, we identified the CHM1(319) peptide as a new candidate target antigen for ET immunotherapy. CONCLUSION: These results clearly identify the ET-derived antigens, EZH2(666) and CHM1(319), as suitable targets for protective allo-restricted human CD8(+) T-cell responses against non-immunogenic ET and may benefit new therapeutic strategies in ET patients treated with allogeneic stem cell transplantation.