These data are in line with and further support the unique mechanism of action by which CCI-006 induces apoptosis in sensitive MLL-r leukemia cells, namely by rapidly inhibiting mitochondrial respiration, thereby inducing mitochondrial membrane depolarization, an UPR and apoptosis in a subset of MLL-r and CALM-AF10 leukemia cells characterized by relatively lower expression levels of MEIS1 and HIF1α (Fig. 7). This evidence concerns the gene MEIS1 and leukemia.