Targeting AML1/ETO-histone deacetylase repressor complex: a novel mechanism for valproic acid-mediated gene expression and cellular differentiation in AML1/ETO-positive acute myeloid leukemia cells.

In t(8;21) acute myeloid leukemia (AML), the AML1/ETO fusion protein promotes leukemogenesis by recruiting class I histone deacetylase (HDAC)-containing repressor complex to the promoter of AML1 target genes. Valproic acid (VPA), a commonly used antiseizure and mood stabilizer drug, has been shown to cause growth arrest and induce differentiation of ...
malignant cells via HDAC inhibition. VPA causes selective proteasomal degradation of HDAC2 but not other class I HDACs (i.e., HDAC 1, 3, and 8). Therefore, we raised the question of whether this drug can effectively target the leukemogenic activity of the AML1/ETO fusion protein that also recruits HDAC1, a key regulator of normal and aberrant histone acetylation. We report here that VPA treatment disrupts the AML1/ETO-HDAC1 physical interaction, stimulates the global dissociation of AML1/ETO-HDAC1 complex from the promoter of AML1/ETO target genes, and induces relocation of both AML1/ETO and HDAC1 protein from nuclear to perinuclear region. Furthermore, we show that mechanistically these effects associate with a significant inhibition of HDAC activity, histone H3 and H4 hyperacetylation, and recruitment of RNA polymerase II, leading to transcriptional reactivation of target genes (i.e., IL-3) otherwise silenced by AML1/ETO fusion protein. Ultimately, these pharmacological effects resulted in significant antileukemic activity mediated by partial cell differentiation and caspase-dependent apoptosis. Taken together, these data support the notion that VPA might effectively target AML1/ETO-driven leukemogenesis through disruption of aberrant HDAC1 function and that VPA should be integrated in novel therapeutic approaches for AML1/ETO-positive AML.
Mesh Terms:
Acetylation, Amino Acid Chloromethyl Ketones, Apoptosis, Caspase 3, Caspase 9, Cell Differentiation, Cell Line, Tumor, Cell Nucleus, Chromatin Assembly and Disassembly, Chromatin Immunoprecipitation, Core Binding Factor Alpha 2 Subunit, Cysteine Proteinase Inhibitors, DNA, Gene Expression Regulation, Leukemic, Histone Deacetylase 1, Histone Deacetylase 2, Histone Deacetylase Inhibitors, Histone Deacetylases, Histones, Humans, Interleukin-3, Leukemia, Myeloid, Acute, Oncogene Proteins, Fusion, Poly(ADP-ribose) Polymerases, Promoter Regions, Genetic, Protein Binding, RNA Polymerase II, Repressor Proteins, Valproic Acid
J. Pharmacol. Exp. Ther.
Date: Jun. 01, 2007
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