Evaluation of the in vitro and in vivo antitumor activity of histone deacetylase inhibitors for the therapy of retinoblastoma.
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.
Dalgard
Clifton Lee
CL
Ocular Oncology Unit, Department of Ophthalmology, University of California at San Francisco, San Francisco, California 94143, USA.
Van Quill
Kurtis R
KR
O'Brien
Joan M
JM
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
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