Complementing mutations in core binding factor leukemias: from mouse models to clinical applications

A great proportion of acute myeloid leukemias (AMLs) display cytogenetic abnormalities including chromosomal aberrations and/or submicroscopic mutations. These abnormalities significantly influence the prognosis of the disease. Hence, a thorough genetic work-up is an essential constituent of standard diagnostic procedures. Core binding factor (CBF) leukemias denote AMLs with chromosomal aberrations disrupting one of the CBF transcription factor genes; the most common examples are translocation t(8;21) and inversion inv(16), which result in the generation of the AML1-ETO and CBFbeta-MYH11 fusion proteins, respectively. However, in murine models, these alterations alone do not suffice to generate full-blown leukemia, but rather, complementary events are required. In fact, a substantial proportion of primary CBF leukemias display additional activating mutations, mostly of the receptor tyrosine kinase (RTK) c-KIT. The awareness of the impact and prognostic relevance of these 'second hits' is increasing with a wider range of mutations tested in clinical trials. Furthermore, novel agents targeting RTKs are emanating rapidly and entering therapeutic regimens. Here, we present a concise review on complementing mutations in CBF leukemias including pathophysiology, mouse models, and clinical implications.