title: Histone deacetylase inhibitors activate NF-kappaB in human leukemia cells through an ATM/NEMO-related pathway.
abstract: Mechanisms underlying histone deacetylase inhibitor (HDACI)-mediated NF-kappaB activation were investigated in human leukemia cells. Exposure of U937 and other leukemia cells to LBH-589 induced reactive oxygen species (ROS) followed by single strand (XRCC1) and double strand (gamma-H2AX) DNA breaks. Notably, LBH-589 lethality was markedly attenuated by small interfering RNA (siRNA) knockdown of the DNA damage-linked histone, H1.2. LBH-589 triggered p65/RelA activation, NF-kappaB-dependent induction of Mn-SOD2, and ROS elimination. Interference with LBH-589-mediated NF-kappaB activation (e.g. in I kappaB alpha super-repressor transfected cells) diminished HDACI-mediated Mn-SOD2 induction and increased ROS accumulation, DNA damage, and apoptosis. The Mn-SOD2 mimetic TBAP (manganese(III)-tetrakis 4-benzoic acid porphyrin) prevented HDACI-induced ROS and NF-kappaB activation while dramatically attenuating DNA damage and cell death. In contrast, TRAF2 siRNA knockdown, targeting receptor-mediated NF-kappaB activation, blocked TNFalpha- but not HDACI-mediated NF-kappaB activation and lethality. Consistent with ROS-mediated DNA damage, LBH-589 exposure activated ATM (on serine 1981) and increased its association with NEMO. Significantly, siRNA NEMO or ATM knockdown blocked HDACI-mediated NF-kappaB activation, resulting in diminished MnSOD2 induction and enhanced oxidative DNA damage and cell death. In accord with the recently described DNA damage/ATM/NEMO pathway, SUMOylation site mutant NEMO (K277A or K309A) cells exposed to LBH-589 displayed diminished ATM/NEMO association, NEMO and p65/RelA nuclear localization/activation, and MnSOD2 up-regulation. These events were accompanied by increased ROS production, gamma-H2AX formation, and cell death. Together, these findings indicate that in human leukemia cells, HDACIs activate the cytoprotective NF-kappaB pathway through an ATM/NEMO/SUMOylation-dependent process involving the induction of ROS and DNA damage and suggest that blocking NF-kappaB activation via the atypical ATM/NEMO nuclear pathway can enhance HDACI antileukemic activity.
authors.affiliation: Departments of Medicine, Richmond, Virginia 23298.
authors.forename: Roberto R
authors.initials: RR
authors.lastname: Rosato
authors.affiliation: Departments of Medicine, Richmond, Virginia 23298.
authors.forename: Sarah S
authors.initials: SS
authors.lastname: Kolla
authors.affiliation: Departments of Medicine, Richmond, Virginia 23298.
authors.forename: Stefanie K
authors.initials: SK
authors.lastname: Hock
authors.affiliation: Departments of Medicine, Richmond, Virginia 23298.
authors.forename: Jorge A
authors.initials: JA
authors.lastname: Almenara
authors.affiliation: Departments of Medicine, Richmond, Virginia 23298.
authors.forename: Ankita
authors.initials: A
authors.lastname: Patel
authors.affiliation: Departments of Medicine, Richmond, Virginia 23298.
authors.forename: Sanjay
authors.initials: S
authors.lastname: Amin
authors.affiliation: Department of Oncology, Novartis Institutes for Biomedical Research, Cambridge, Massachusetts 02139.
authors.forename: Peter
authors.initials: P
authors.lastname: Atadja
authors.affiliation: Human and Molecular Genetics, Richmond, Virginia 23298; Virginia Commonwealth University Institute of Molecular Medicine, Virginia Commonwealth University, Richmond, Virginia 23298.
authors.forename: Paul B
authors.initials: PB
authors.lastname: Fisher
authors.affiliation: Biochemistry, the Massey Cancer Center, Richmond, Virginia 23298; Virginia Commonwealth University Institute of Molecular Medicine, Virginia Commonwealth University, Richmond, Virginia 23298.
authors.forename: Paul
authors.initials: P
authors.lastname: Dent
authors.affiliation: Departments of Medicine, Richmond, Virginia 23298; Biochemistry, the Massey Cancer Center, Richmond, Virginia 23298; Virginia Commonwealth University Institute of Molecular Medicine, Virginia Commonwealth University, Richmond, Virginia 23298. Electronic address: stgrant@vcu.edu.
authors.forename: Steven
authors.initials: S
authors.lastname: Grant
mesh_terms: D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000378:metabolism; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000378:metabolism; D004789:Enzyme Activation; D015971:Gene Expression Regulation, Enzymologic; D015973:Gene Expression Regulation, Leukemic; D018922:HL-60 Cells; D056572:Histone Deacetylase Inhibitors / Q000378:metabolism*; D006801:Humans; D051550:I-kappa B Kinase / Q000378:metabolism; D019169:Jurkat Cells; D007938:Leukemia / Q000188:drug therapy* / Q000201:enzymology*; D009154:Mutation; D016328:NF-kappa B / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D017382:Reactive Oxygen Species; D025842:SUMO-1 Protein / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000378:metabolism; D020298:U937 Cells
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D056572:Histone Deacetylase Inhibitors; C491731:IKBKG protein, human; D016328:NF-kappa B; D017382:Reactive Oxygen Species; D025842:SUMO-1 Protein; C495501:SUMO1 protein, human; D025521:Tumor Suppressor Proteins; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases; D051550:I-kappa B Kinase