A highly prevalent rearrangement found in AML occurs in the gene loci encoding members of the core-binding factor (CBF) complex, consisting of a heterodimeric transcription factor complex composed of a member of the RUNX DNA binding factor family (CBFα/ AML1/ RUNX1) and a non-DNA binding partner termed CBFβ [3]. This evidence concerns the gene CEBPZ and acute myeloid leukemia.