title: Radiosensitizing effect of a phenylbutyrate-derived histone deacetylase inhibitor in hepatocellular carcinoma.
abstract: OBJECTIVE
  Radiotherapy is integrated into the multimodal treatment of localized hepatocellular carcinoma (HCC) refractory to conventional treatment. Tumor control remains unsatisfactory and the sublethal effect associates with secondary spread. The use of an effective molecularly targeted agent in combination with radiotherapy is a potential therapeutic approach. Our aim was to assess the effect of combining a phenylbutyrate-derived histone deacetylase (HDAC) inhibitor, AR-42, with radiotherapy in in vitro and in vivo models of human HCC.
  
  
  METHODS
  Human HCC cell lines (Huh-7 and PLC-5) were used to evaluate the in vitro synergism of combining AR-42 with irradiation. Flow cytometry analyzed the cell cycle changes, whereas Western blot investigated the protein expressions after the combined treatment. Severe combined immunodeficient (SCID) mice bearing ectopic and orthotopic HCC xenografts were treated with AR-42 and/or radiotherapy for the in vivo response.
  
  
  RESULTS
  AR-42 significantly enhanced radiation-induced cell death by the inhibition of the DNA end-binding activity of Ku70, a highly versatile regulatory protein for DNA repair, telomere maintenance, and apoptosis. In ectopic xenografts of Huh-7 and PLC-5, pretreatment with AR-42 significantly enhanced the tumor-suppressive effect of radiotherapy by 48% and 66%, respectively. A similar combinatorial effect of AR-42 (10 and 25 mg/kg) and radiotherapy was observed in Huh-7 orthotopic model of tumor growth by 52% and 82%, respectively. This tumor suppression was associated with inhibition of intratumoral Ku70 activity as well as reductions in markers of HDAC activity and proliferation, and increased apoptosis.
  
  
  CONCLUSIONS
  AR-42 is a potent, orally bioavailable inhibitor of HDAC with therapeutic value as a radiosensitizer of HCC.
authors.affiliation: Department of Oncology, National Taiwan University Hospital, Taipei, Taiwan.
authors.forename: Yen-Shen
authors.initials: YS
authors.lastname: Lu
authors.forename: Chia-Hung
authors.initials: CH
authors.lastname: Chou
authors.forename: Kai-Yuan
authors.initials: KY
authors.lastname: Tzen
authors.forename: Ming
authors.initials: M
authors.lastname: Gao
authors.forename: Ann-Lii
authors.initials: AL
authors.lastname: Cheng
authors.forename: Samuel K
authors.initials: SK
authors.lastname: Kulp
authors.forename: Jason Chia-Hsien
authors.initials: JC
authors.lastname: Cheng
mesh_terms: D000107:Acetylation; D000818:Animals; D034961:Antigens, Nuclear / Q000378:metabolism; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy / Q000532:radiotherapy*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000528:radiation effects; D003037:Cobalt Radioisotopes / Q000627:therapeutic use; D003131:Combined Modality Therapy / Q000379:methods; D004260:DNA Repair / Q000187:drug effects*; D004273:DNA, Neoplasm / Q000187:drug effects / Q000378:metabolism / Q000528:radiation effects; D004268:DNA-Binding Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D056572:Histone Deacetylase Inhibitors / Q000627:therapeutic use*; D006801:Humans; D000072200:Ku Autoantigen; D008113:Liver Neoplasms / Q000188:drug therapy / Q000532:radiotherapy*; D008297:Male; D051379:Mice; D016513:Mice, SCID; D058990:Molecular Targeted Therapy / Q000379:methods; D010654:Phenylbutyrates / Q000627:therapeutic use*; D011838:Radiation-Sensitizing Agents / Q000627:therapeutic use*; D011879:Radiotherapy Dosage; D011897:Random Allocation; D014183:Transplantation, Heterologous
chemical_list: D034961:Antigens, Nuclear; D003037:Cobalt Radioisotopes; D004273:DNA, Neoplasm; D004268:DNA-Binding Proteins; D056572:Histone Deacetylase Inhibitors; C529674:OSU-HDAC42 compound; D010654:Phenylbutyrates; D011838:Radiation-Sensitizing Agents; C000606509:Xrcc6 protein, human; C000606510:Xrcc6 protein, mouse; D000072200:Ku Autoantigen