Lack or mutation of one of the complex members (RUNX1 in t(8;21)(q22;q22.1) AML or CBFB in inv(16)(p13.1q22) AML) results in a dominant negative inhibitory effect on CBF complex formation and impairment of hematopoiesis [5, 6]. This evidence concerns the gene CBFB and acute myeloid leukemia.