AML HLA Ligandome reveals mutated NPM1 as a recurrent neoantigen

Somatic mutations in cancer are a potential source of cancer specific neoantigens. Acute myeloid leukemia (AML) has common recurrent mutations shared between patients in addition to private mutations specific to individuals. We hypothesized that neoantigens derived from recurrent shared mutations would be attractive targets for future immunotherapy and sought to study the Class I and II HLA ligandomes of thirteen primary AML tumor samples and two AML cell lines (OCI-AML3 and MV4-11) using mass spectrometry. We identified two endogenous, mutation-bearing HLA Class I ligands from NPM1, which are predicted to bind the common HLA haplotypes, HLA-A*03:01 and HLA-A*02:01 respectively. We further derived CD8+ T cells from healthy donor peripheral blood samples which bound mutant-peptide loaded A*03:01 and A*02:01 tetramers, suggesting a new source of NPM1 mutation-specific T cell receptors (TCRs) for future evaluation. Since NPM1 is mutated in approximately one-third of patients with AML, the finding of endogenous NPM1 neoantigens supports future studies evaluating immunotherapeutic approaches against this target, for this subset of patients with AML.