DNA demethylation-mediated downregulation of MNX1 in acute myeloid leukemia

To the Editor:Acute myeloid leukemia (AML), an aggressive hematological malignancy, is frequently associated with mutations in genes encoding enzymes that regulate epigenetic patterns.Additionally, AML is associated with genomic rearrangements, including translocations [1].Structural rearrangements can activate oncogenes by repositioning cis-regulatory elements into the vicinity of genes, normally not expressed in a certain cell lineage, a mechanism termed enhancer hijacking [2].For example, in the AML-M4 cell line GDM-1, the oncogenic transcription factor Motor Neuron and Pancreas Homeobox 1 (MNX1) [3,4] is aberrantly activated through enhancer hijacking due to a translocation t(6;7) which juxtaposes MNX1 on chromosome 7 (chr7) with enhancers from the MYB-AHI1 region on chr6 [3][4][5].Similarly, MNX1 activation mainly by enhancer hijacking involving various hematopoietic enhancers is a rare but recurrent event and occurs in 1.4% of primary AML [6,7].In this study, we hypothesized that therapeutic downregulation of MNX1 could be achieved by an epigenetic compound disrupting the promoter-enhancer interaction.We first demonstrated with two MNX1-targeting shRNAs that MNX1 downregulation (Supplementary Fig. 1A) reduces GDM-1 viability (Supplementary Fig. 1B).This confirms a previous finding and suggests that MNX1 activation is required for leukemic growth [3].To identify compounds that can reduce MNX1 expression, we screened a focused compound library of 174 epigenetic tool compounds including approved drugs in GDM-1 cells (Supplementary Table 1a,b).Twenty-one compounds reduced viability by approximately 70% (Fig. 1A).Based on their diverse modes of action, effectiveness, and commercial availability, we selected ten compounds mediating reduced viability and determined the IC 80 concentrations.Of these compounds, only 5-aza-2'-deoxycitidine (decitabine, DAC), a DNA methyltransferase (DNMT) inhibitor in clinical use in myelodysplastic syndrome and other hematological