Deregulation of the HOXA9/MEIS1 Axis in Acute Leukemia

Abstract

Purpose of review HOXA9 is a homeodomain transcription factor that plays an essential role in normal hematopoiesis and acute leukemia, where its over expression is strongly correlated with poor prognosis. This review highlights recent advances in the understanding of genetic alterations leading to deregulation of HOXA9 and the downstream mechanisms of HOXA9-mediated transformation. Recent findings A variety of genetic alterations including MLL-translocations, NUP98-fusions, NPM1 mutations, CDX deregulation, and MOZ-fusions lead to high level HOXA9 expression in acute leukemias. The mechanisms resulting in HOXA9 over expression are beginning to be defined and represent attractive therapeutic targets. Small molecules targeting MLL-fusion protein complex members, such as DOT1L and menin, have shown promising results in animal models, and a DOT1L inhibitor is currently being tested in clinical trials. Essential HOXA9 cofactors and collaborators are also being identified, including transcription factors PU.1 and C/EBPα, which are required for HOXA9-driven leukemia. HOXA9 targets including IGF1, CDX4, INK4A/INK4B/ARF, mir-21 and mir-196b and many others provide another avenue for potential drug development. Summary HOXA9 deregulation underlies a large subset of aggressive acute leukemias. Understanding the mechanisms regulating the expression and activity of HOXA9, along with its critical downstream targets, shows promise for the development of more selective and effective leukemia therapies.