By analyzing RNA-seq data previously collected from six MLL::AF4-rearranged samples that underwent a B-ALL-to-AML lineage-switching event10, we found the B-ALL-specific oncoprotein-target genes are expressed at significantly higher levels in all six patient-matched B-ALL samples (Fig. 6a). This evidence concerns the gene AFF1 and precursor B-cell acute lymphoblastic leukemia.