title: Antitumor activity of arsenic trioxide on retinoblastoma: cell differentiation and apoptosis depending on arsenic trioxide concentration.
abstract: OBJECTIVE
  Arsenic trioxide (ATO) targets multiple pathways in malignant cells, resulting in the promotion of differentiation or in the induction of apoptosis. The antitumor activity of ATO on retinoblastoma was investigated.
  
  
  METHODS
  Human retinoblastoma cells were incubated with various ATO concentrations. The antiproliferative effect of ATO was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, and the effect of ATO on cell-cycle progression was validated by flow cytometry. At a low concentration, the ATO-induced differentiation of retinoblastoma cells was evaluated by neurofilament expression and extracellular signal-regulated kinase (ERK)1/2 activation, which was confirmed by the inhibition of ERK1/2. At a high concentration, ATO-induced H(2)O(2) production was investigated with the cell-permeable fluorescent dye 2'7'-dichlorofluorescein-diacetate, and the relationship of ATO-induced H(2)O(2) production with caspase-3-dependent apoptosis was validated by Western blot and 4'6-diamidino-2-phenolindole staining, which was confirmed by reactive oxygen species (ROS) inhibition. The effect of ATO on tumor formation was assessed with an orthotopic animal model of retinoblastoma.
  
  
  RESULTS
  The antitumor activity of ATO in retinoblastoma was related to two main mechanisms, differentiation and apoptosis, which were determined by the level of ATO. At a low dose (<or= 1 microM), ATO induced the differentiation of retinoblastoma cells through ERK1/2 activation, whereas ROS generation by a high dose (>or= 2 microM) of ATO induced apoptosis in retinoblastoma cells. Moreover, ATO at low and high doses effectively inhibited tumor formation.
  
  
  CONCLUSIONS
  These results suggest that ATO can be used as an effective alternative therapeutic for the treatment of retinoblastoma.
authors.affiliation: Department of Ophthalmology, Seoul National University College of Medicine, Seoul, Korea.
authors.forename: Jeong Hun
authors.initials: JH
authors.lastname: Kim
authors.forename: Jin Hyoung
authors.initials: JH
authors.lastname: Kim
authors.forename: Young Suk
authors.initials: YS
authors.lastname: Yu
authors.forename: Dong Hun
authors.initials: DH
authors.lastname: Kim
authors.forename: Chong Jai
authors.initials: CJ
authors.lastname: Kim
authors.forename: Kyu-Won
authors.initials: KW
authors.lastname: Kim
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000008:administration & dosage* / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D000077237:Arsenic Trioxide; D001152:Arsenicals / Q000008:administration & dosage* / Q000494:pharmacology; D015153:Blotting, Western; D053148:Caspase 3 / Q000378:metabolism; D002453:Cell Cycle; D002454:Cell Differentiation / Q000187:drug effects*; D049109:Cell Proliferation / Q000187:drug effects; D005434:Flow Cytometry; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3 / Q000378:metabolism; D010087:Oxides / Q000008:administration & dosage* / Q000494:pharmacology; D010766:Phosphorylation; D019572:Retinal Neoplasms / Q000188:drug therapy / Q000473:pathology*; D012175:Retinoblastoma / Q000188:drug therapy / Q000473:pathology*; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D001152:Arsenicals; D010087:Oxides; D006861:Hydrogen Peroxide; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D053148:Caspase 3; D000077237:Arsenic Trioxide