title: Histone deacetylase inhibitors valproic acid and depsipeptide sensitize retinoblastoma cells to radiotherapy by increasing H2AX phosphorylation and p53 acetylation-phosphorylation.
abstract: Although p53 is intact in most cases of retinoblastoma, it is largely inactivated by the ubiqutin-proteasome system through interaction with murine double minute 2 (MDM2) and murine double minute X (MDMX). The present study showed that the histone deacetylase (HDAC) inhibitors valproic acid (VPA) and depsipeptide (FK228) synergistically enhanced ionizing radiation (IR)-induced apoptosis, associated with activation of caspase-3 and cleavage of poly(ADP-ribose) polymerase in Y79 and WER1-Rb1 human retinoblastoma cells. Both VPA and FK228 enhanced IR-induced phosphorylation of histone H2AX on Ser139 preceding apoptosis. Exposure of cells to IR in the presence of VPA or FK228 induced the accumulation of p53 acetylated at Lys382 and phosphorylated at Ser46 through the reduction of binding affinity with MDM2 and MDMX. These results suggest that acetylation of p53 by HDAC inhibitors is a promising new therapeutic target in refractory retinoblastoma.
authors.affiliation: Division of Molecular Genetics, Institute of DNA Medicine, Jikei University School of Medicine, Minato-ku, Tokyo 105-8461, Japan.
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kawano
authors.forename: Masaharu
authors.initials: M
authors.lastname: Akiyama
authors.forename: Miyuki
authors.initials: M
authors.lastname: Agawa-Ohta
authors.forename: Yoko
authors.initials: Y
authors.lastname: Mikami-Terao
authors.forename: Satsuki
authors.initials: S
authors.lastname: Iwase
authors.forename: Takaaki
authors.initials: T
authors.lastname: Yanagisawa
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Ida
authors.forename: Naoki
authors.initials: N
authors.lastname: Agata
authors.forename: Hisashi
authors.initials: H
authors.lastname: Yamada
mesh_terms: D000107:Acetylation; D017209:Apoptosis / Q000187:drug effects / Q000528:radiation effects; D053148:Caspase 3 / Q000378:metabolism; D018797:Cell Cycle Proteins; D045744:Cell Line, Tumor; D047630:Depsipeptides / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004307:Dose-Response Relationship, Radiation; D056572:Histone Deacetylase Inhibitors / Q000494:pharmacology*; D006655:Histone Deacetylases / Q000378:metabolism*; D006657:Histones / Q000378:metabolism*; D006801:Humans; D009687:Nuclear Proteins / Q000378:metabolism; D010766:Phosphorylation; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011499:Protein Processing, Post-Translational / Q000187:drug effects / Q000528:radiation effects; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051736:Proto-Oncogene Proteins c-mdm2 / Q000378:metabolism; D011838:Radiation-Sensitizing Agents / Q000494:pharmacology*; D012175:Retinoblastoma / Q000201:enzymology* / Q000473:pathology; D012694:Serine; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D014635:Valproic Acid / Q000494:pharmacology*
chemical_list: D018797:Cell Cycle Proteins; D047630:Depsipeptides; C468783:H2AX protein, human; D056572:Histone Deacetylase Inhibitors; D006657:Histones; C482775:MDM4 protein, human; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D011838:Radiation-Sensitizing Agents; C495901:TP53 protein, human; D016159:Tumor Suppressor Protein p53; D012694:Serine; D014635:Valproic Acid; C087123:romidepsin; C497206:MDM2 protein, human; D051736:Proto-Oncogene Proteins c-mdm2; D011065:Poly(ADP-ribose) Polymerases; C505407:CASP3 protein, human; D053148:Caspase 3; D006655:Histone Deacetylases