title: Normoxically overexpressed hypoxia inducible factor 1-alpha is involved in arsenic trioxide resistance acquisition in hepatocellular carcinoma.
abstract: BACKGROUND
  The aim of this study was to examine the underlying signaling mechanisms of arsenic trioxide (ATO)-mediated anticancer effects and the responsible biomarker(s) for the acquired resistance in human heptatocellular carcinoma (HCC).
  
  
  METHODS
  The therapeutic effects of ATO were examined using 2 characteristically distinct HCC cell lines, Hep-J5 (overexpressing HIF-1α/GRP78) and SK-Hep-1 (the matched control). ATO-mediated proliferation inhibition, oxidative stress, and apoptosis were analyzed using flowcytometric analysis and western blotting. The role of HIF-1α and GRP78 in HCC resistance to ATO treatment was determined using RNA silencing and inhibitor approaches.
  
  
  RESULTS
  SK-Hep-1 cells, lacking both HIF-1α and GRP78 expressions were responsive to ATO-induced apoptosis via an oxidative-nitrosative mechanism. Intracellular glutathione depletion and lipid peroxidation have been identified as the early cascade of events preceding apoptosis via cytochrome c release and the severe drop of mitochondrial membrane potential (MMP). Conversely, Hep-J5 cells, with normoxic coexpression of HIF-1α and GRP78, were resistant to ATO-induced apoptosis. GRP78-silenced Hep-J5 cells remained resistant to ATO treatment. In contrast, ATO resistance in Hep-J5 cells was overcome by the addition of YC-1, a HIF-1α inhibitor.
  
  
  CONCLUSIONS
  HIF-1α was identified as the major positive modifier for ATO resistance acquisition in HCC, and it represents a prime molecular target for overcoming ATO resistance.
authors.affiliation: Institute of Medicine, Chung Shan Medical University, Taichung, Taiwan.
authors.forename: Jia-Nien
authors.initials: JN
authors.lastname: Tung
authors.forename: Ya-Wen
authors.initials: YW
authors.lastname: Cheng
authors.forename: Chung-Huei
authors.initials: CH
authors.lastname: Hsu
authors.forename: Tsan-Zon
authors.initials: TZ
authors.lastname: Liu
authors.forename: Pei-Ying
authors.initials: PY
authors.lastname: Hsieh
authors.forename: Lai-Lei
authors.initials: LL
authors.lastname: Ting
authors.forename: Hui-Ling
authors.initials: HL
authors.lastname: Ko
authors.forename: Yu-Jia
authors.initials: YJ
authors.lastname: Chang
authors.forename: Jeng-Fong
authors.initials: JF
authors.lastname: Chiou
authors.forename: Alexander T H
authors.initials: AT
authors.lastname: Wu
mesh_terms: D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects; D000077237:Arsenic Trioxide; D001152:Arsenicals / Q000494:pharmacology*; D015153:Blotting, Western; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy* / Q000378:metabolism / Q000473:pathology; D053148:Caspase 3 / Q000378:metabolism; D053179:Caspase 7 / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D019008:Drug Resistance, Neoplasm; D000091342:Endoplasmic Reticulum Chaperone BiP; D004789:Enzyme Activation / Q000187:drug effects; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D006360:Heat-Shock Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000378:metabolism*; D015227:Lipid Peroxidation / Q000187:drug effects; D008113:Liver Neoplasms / Q000188:drug therapy / Q000378:metabolism / Q000473:pathology; D053078:Membrane Potential, Mitochondrial / Q000187:drug effects; D009569:Nitric Oxide / Q000378:metabolism; D010087:Oxides / Q000494:pharmacology*; D010100:Oxygen / Q000378:metabolism*; D017382:Reactive Oxygen Species / Q000378:metabolism; D014407:Tumor Cells, Cultured
chemical_list: D000970:Antineoplastic Agents; D001152:Arsenicals; D000091342:Endoplasmic Reticulum Chaperone BiP; C497442:HIF1A protein, human; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D010087:Oxides; D017382:Reactive Oxygen Species; D009569:Nitric Oxide; D053148:Caspase 3; D053179:Caspase 7; D000077237:Arsenic Trioxide; D010100:Oxygen