Differentiation
therapy has emerged as a powerful way to target specific
hematologic malignancies. One of the best examples is the use of
all-trans retinoic acid (ATRA) in
acute promyelocytic leukemia (APL), which has significantly improved the outcome for patients with this specific form of
acute myeloid leukemia (AML). In considering how differentiation
therapy could be used in other forms of AML, we predicted that compounds that induce terminal differentiation of megakaryocytes would be effective
therapies for the megakaryocytic form of AML, named
acute megakaryocytic leukemia (AMKL). We also speculated that such agents would reduce the burden of abnormal hematopoietic cells in
primary myelofibrosis and alter the differentiation of megakaryocytes in
myelodysplastic syndromes. Using a high-throughput chemical screening approach, we identified small molecules that promoted many features of terminal megakaryocyte differentiation, including the induction of polyploidization, the process by which cells accumulate
DNA to 32N or greater. As the induction of polyploidization is an irreversible process, cells that enter this form of the cell cycle do not divide again. Thus, this would be an effective way to reduce the
tumor burden. Clinical studies with
polyploidy inducers, such as
aurora kinase A inhibitors, are under way for a wide variety of
malignancies, whereas trials specifically for AMKL and PMF are in development. This novel form of differentiation
therapy may be clinically available in the not-too-distant future. Clin
Cancer Res; 19(22); 6084-8. ©2013 AACR.