Acute myeloid leukemia requires Hhex to enable PRC2-mediated epigenetic repression of Cdkn2a (RNA-Seq)

Unlike clustered HOX genes, the role of non-clustered homeobox gene family members in hematopoiesis and leukemogenesis has not been extensively studied. Here we find that the Hematopoietically-expressed Homeobox gene, Hhex, is overexpressed in acute myeloid leukemia (AML) and is essential for the initiation and propagation of MLL-ENL induced AML, but dispensable for normal myelopoiesis, indicating a specific requirement for Hhex for leukemic growth. Loss of Hhex leads to upregulated expression of the tumor suppressors p16INK4a and p19ARF, which are required for growth arrest and myeloid differentiation following Hhex deletion. Mechanistically, we show that Hhex binds to the Cdkn2a locus and is required for H3K27Me3-mediated repression of this locus. Thus, Hhex is a novel therapeutic target that is specifically required for AML stem cells to repress tumor suppressor pathways and enable continued self-renewal. Overall design: Transcriptional profiling of MLL-ENL Hhex-/fl and MLL-ENL Hhex+/fl leukemia cells using RNA sequencing