Identification of NM23-H2 as a tumour-associated antigen in chronic myeloid leukaemia

Therapeutic effects of haematopoietic stem cell transplantation are not limited to maximal chemoradiotherapy and subsequent bone marrow regeneration, but include specific as well as unspecific immune reactions known as graft-versus-leukaemia (GvL) effects. Specific immune reactions are likely to be particularly relevant to the long-term treatment of diseases, such as chronic myeloid leukaemia (CML), in which residual cells may remain quiescent and unresponsive to cytotoxic and molecular therapies for long periods of time. Specific GvL effects result from the expression on leukaemic cells of specific tumour-associated antigens (TAAs) in the context of HLA proteins. As human leukocyte antigen (HLA) types vary widely, the development of broadly applicable tumour vaccines will require the identification of multiple TAAs active in different HLA backgrounds. Here, we describe the identification of NM23-H2 as a novel HLA-A32-restricted TAA of CML cells and demonstrate the presence of specifically reactive T cells in a patient 5 years after transplantation. As the NM23 proteins are aberrantly expressed in a range of different tumours, our findings suggest potential applications beyond CML and provide a new avenue of investigation into the molecular mechanisms underlying CML.