title: Evaluation of the in vitro and in vivo antitumor activity of histone deacetylase inhibitors for the therapy of retinoblastoma.
abstract: OBJECTIVE
  To evaluate the potential utility of histone deacetylase inhibitors (HDACi) for treatment of retinoblastoma (RB).
  
  
  METHODS
  Growth-inhibitory effects of HDACi [trichostatin A (TSA), suberoylanilide hydroxamic acid (SAHA), or MS-275] were assessed in human and transgenic murine RB cells. Effects of TSA and MS-275 were also assessed in combination with standard therapeutic agents for RB. Proapoptotic effects of MS-275 and TSA were evaluated by caspase-3/7 activity, Annexin V translocation, and/or Bim expression analyses. Effects of MS-275 on cell cycle distribution and reactive oxygen species levels were determined by flow cytometry. Retinal tissue morphology was evaluated in mice after local administration of MS-275. Analysis of retinal acetyl-histone levels was used to assess MS-275 delivery after systemic administration. Therapeutic effects of MS-275 were determined in transgenic mouse and rat ocular xenograft models of RB after i.p. injection of 20 mg/kg every other day for 21 or 13 days, respectively.
  
  
  RESULTS
  TSA, SAHA, and MS-275 dose dependently reduced RB cell survival. TSA and MS-275 showed additive growth-inhibitory effects in combination with carboplatin, etoposide, or vincristine. TSA and MS-275 increased caspase-3/7 activity. MS-275 increased Annexin V membrane translocation and induced G1 arrest. Cytotoxicity of MS-275 was dependent on increased reactive oxygen species levels and was reversed by antioxidant pretreatment. Intraocular administration of 1 microL of 10 micromol/L MS-275 did not alter ocular tissue morphology. Increased acetyl-histone levels confirmed MS-275 delivery to retinal tissue after systemic administration. MS-275 significantly reduced tumor burden in both mouse and rat models of RB.
  
  
  CONCLUSIONS
  HDACi should be considered for clinical trials in children with RB.
authors.affiliation: Ocular Oncology Unit, Department of Ophthalmology, University of California at San Francisco, San Francisco, California 94143, USA.
authors.forename: Clifton Lee
authors.initials: CL
authors.lastname: Dalgard
authors.forename: Kurtis R
authors.initials: KR
authors.lastname: Van Quill
authors.forename: Joan M
authors.initials: JM
authors.lastname: O'Brien
mesh_terms: D000818:Animals; D017304:Annexin A5 / Q000187:drug effects; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D001549:Benzamides / Q000494:pharmacology; D015153:Blotting, Western; D053148:Caspase 3 / Q000187:drug effects; D053179:Caspase 7 / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D005434:Flow Cytometry; D056572:Histone Deacetylase Inhibitors; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology; D066298:In Vitro Techniques; D051379:Mice; D008822:Mice, Transgenic; D016133:Polymerase Chain Reaction; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D017382:Reactive Oxygen Species / Q000378:metabolism; D019572:Retinal Neoplasms / Q000188:drug therapy*; D012175:Retinoblastoma / Q000188:drug therapy*; D000077337:Vorinostat; D023041:Xenograft Model Antitumor Assays
chemical_list: D017304:Annexin A5; D000970:Antineoplastic Agents; D001549:Benzamides; D004791:Enzyme Inhibitors; D056572:Histone Deacetylase Inhibitors; D006877:Hydroxamic Acids; D011725:Pyridines; D017382:Reactive Oxygen Species; C118739:entinostat; C012589:trichostatin A; D000077337:Vorinostat; D053148:Caspase 3; D053179:Caspase 7