A T-cell receptor targeting RUNX1 frameshift mutations in acute myeloid leukemia

Runt-related transcription factor 1 (RUNX1) is a key regulator of hematopoietic differentiation. RUNX1 mutations in acute myeloid leukemia (AML) are associated with poor prognosis. One-third are frameshift mutations encoding an oncogenic protein with an elongated C-terminus translated in an alternative reading frame. Here, we investigated whether the alternative reading frame of oncogenic RUNX1 can be targeted by immunotherapy. We introduced a construct with a RUNX1 frameshift mutation into B-cell lines with common HLA class I alleles and identified 13 neopeptides by immunopeptidomics. To investigate whether these peptides are neoantigens, peptide-MHC tetramers were used to screen healthy individuals for RUNX1 neoantigen-specific CD8 T cells. T-cell clones were isolated against 5 neoantigens in 4 HLA alleles. Two neoantigens were recognized on an HLA-B*07:02-positive AML cell line with an endogenous RUNX1 frameshift mutation. The T-cell receptors (TCRs) of these clones were sequenced, and analyzed after transfer into CD8 T cells. One TCR induced effective killing of RUNX1-mutated AML cells in vitro and in immunodeficient mice. TCR-engineered T cells also killed patient-derived AML cells, including leukemic stem cells. In conclusion, we showed that RUNX1 frameshift mutations can be effectively targeted, demonstrating the potential relevance of TCR-based immunotherapy to treat patients with RUNX1-mutated AML.