title: Different induction of GRP78 and CHOP as a predictor of sensitivity to proteasome inhibitors in thyroid cancer cells.
abstract: Proteasome inhibitors represent a novel class of antitumor agents with preclinical and clinical evidence of activity against hematological malignancies and solid tumors. Emerging lines of evidence suggest that the unfolded protein response is implicated in proteasome inhibitors-induced apoptosis. Glucose-regulated protein 78 kDa (GRP78) and CCAAT/enhancer-binding protein homologous protein (CHOP) as part of the unfolded protein response play critical roles in cell survival or death. Here we demonstrate that induction of GRP78 and CHOP are differently regulated upon proteasome inhibition in different thyroid cancer cell lines, and GRP78 levels as well as preferential induction of GRP78 or CHOP appears to be involved in the responsiveness. Insensitive ARO, 8305C, and 8505C cell lines inherently express relatively high levels of GRP78 compared with sensitive cell lines, and its levels are further up-regulated upon treatment with proteasome inhibitors. CHOP levels are dramatically induced in sensitive cell lines until 24 h after proteasome inhibition. On the other hand, only a slight increase is observed at 4 h in insensitive cell lines, and this increase is unable to be detected after 8 h. Insensitive cells are sensitized to proteasome inhibition by suppression of GRP78. Furthermore, suppression of CHOP induction or overexpression of GRP78 partially prevents proteasome inhibition-mediated cell death. Our study indicates a molecular mechanism by which the sensitivity of thyroid cancer cells is regulated by the level of GRP78 as well as preferential induction of GRP78 or CHOP upon treatment with proteasome inhibitors. Our experiments therefore suggest a novel approach toward sensitization of thyroid cancer cells to proteasome inhibitors.
authors: Department of Molecular Biology, the First Affiliated Hospital, China Medical University, Shenyang 110001, China.
authors: Hua-Qin
authors: HQ
authors: Wang
authors: Zhen-Xian
authors: ZX
authors: Du
authors: Hai-Yan
authors: HY
authors: Zhang
authors: Da-Xin
authors: DX
authors: Gao
mesh_terms: D015153:Blotting, Western; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology*; D000091342:Endoplasmic Reticulum Chaperone BiP; D015870:Gene Expression / Q000187:drug effects; D006360:Heat-Shock Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007976:Leupeptins / Q000494:pharmacology; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism*; D009842:Oligopeptides / Q000494:pharmacology; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D061988:Proteasome Inhibitors; D034622:RNA Interference; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013964:Thyroid Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D051742:Transcription Factor CHOP / Q000235:genetics / Q000378:metabolism*
chemical_list: D015853:Cysteine Proteinase Inhibitors; C497249:DDIT3 protein, human; D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; D007976:Leupeptins; D018832:Molecular Chaperones; D009842:Oligopeptides; D061988:Proteasome Inhibitors; C090535:benzyloxycarbonyl-isoleucyl-glutamyl(O-tert-butyl)-alanyl-leucinal; D051742:Transcription Factor CHOP; D046988:Proteasome Endopeptidase Complex; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde