title: Role of oxidative stress and intracellular glutathione in the sensitivity to apoptosis induced by proteasome inhibitor in thyroid cancer cells.
abstract: BACKGROUND
  The proteasome inhibitor bortezomib has shown impressive clinical activity alone and in combination with conventional and other novel agents for the treatment of multiple myeloma (MM) and some solid cancers. Although bortezomib is known to be a selective proteasome inhibitor, the downstream mechanisms of cytotoxicity and drug resistance are poorly understood.
  
  
  METHODS
  Proteasome activity, intracellular glutathione (GSH) and ROS levels, as well as activities of GSH synthesis enzymes were measured using spectrophotometric methods. Cell death was analyzed using flow cytometry and caspase activity assay. The expression level of GSH synthesis enzymes were measured using real-time RT-PCR.
  
  
  RESULTS
  At concentrations that effectively inhibited proteasome activity, bortezomib induced apoptosis in FRO cells, but not in ARO cells. Bortezomib elevated the amount of glutathione (GSH) and the treatment with bortezomib increased the level of mRNA for GCL, a rate-limiting enzyme in glutathione synthesis. Furthermore, depletion of GSH increases apoptosis induced by bortezomib, in contrast, repletion of GSH decreases bortezomib-mediated cell death.
  
  
  CONCLUSIONS
  GSH protects cells from proteasome inhibition-induced oxidative stress and glutathione-dependent redox system might play an important role in the sensitivity to proteasome inhibition-induced apoptosis.
authors.affiliation: Department of Biochemistry and Molecular Biology, China Medical University, Shenyang, PR China. dzx_doctor@hotmail.com
authors.forename: Zhen-Xian
authors.initials: ZX
authors.lastname: Du
authors.forename: Hai-Yan
authors.initials: HY
authors.lastname: Zhang
authors.forename: Xin
authors.initials: X
authors.lastname: Meng
authors.forename: Yifu
authors.initials: Y
authors.lastname: Guan
authors.forename: Hua-Qin
authors.initials: HQ
authors.lastname: Wang
mesh_terms: D014013:1,2-Dihydroxybenzene-3,5-Disulfonic Acid Disodium Salt / Q000494:pharmacology; D000255:Adenosine Triphosphate / Q000378:metabolism; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D001897:Boronic Acids / Q000494:pharmacology*; D000069286:Bortezomib; D020134:Catalytic Domain / Q000235:genetics; D045744:Cell Line, Tumor; D005434:Flow Cytometry; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D005721:Glutamate-Cysteine Ligase / Q000235:genetics / Q000378:metabolism; D005978:Glutathione / Q000378:metabolism*; D005981:Glutathione Synthase / Q000235:genetics / Q000378:metabolism; D006801:Humans; D042541:Intracellular Space / Q000187:drug effects / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects* / Q000502:physiology; D011480:Protease Inhibitors / Q000494:pharmacology; D061988:Proteasome Inhibitors; D011719:Pyrazines / Q000494:pharmacology*; D017382:Reactive Oxygen Species / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013053:Spectrophotometry / Q000379:methods; D013964:Thyroid Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology
chemical_list: D001897:Boronic Acids; D011480:Protease Inhibitors; D061988:Proteasome Inhibitors; D011719:Pyrazines; D017382:Reactive Oxygen Species; D014013:1,2-Dihydroxybenzene-3,5-Disulfonic Acid Disodium Salt; D000069286:Bortezomib; D000255:Adenosine Triphosphate; D005721:Glutamate-Cysteine Ligase; D005981:Glutathione Synthase; D005978:Glutathione