title: Inhibition of glioma growth by minocycline is mediated through endoplasmic reticulum stress-induced apoptosis and autophagic cell death.
abstract: BACKGROUND
  We have reported that minocycline (Mino) induced autophagic death in glioma cells. In the present study, we characterize the upstream regulators that control autophagy and switch cell death from autophagic to apoptotic.
  
  
  METHODS
  Western blotting and immunofluorescence were used to detect the expressions of eukaryotic translation initiation factor 2α (eIF2α), transcription factor GADD153 (CHOP), and glucose-regulated protein 78 (GRP78). Short hairpin (sh)RNA was used to knock down eIF2α or CHOP expression. Autophagy was assessed by the conversion of light chain (LC)3-I to LC3-II and green fluorescent protein puncta formation. An intracranial mouse model and bioluminescent imaging were used to assess the effect of Mino on tumor growth and survival time of mice.
  
  
  RESULTS
  The expression of GRP78 in glioma was high, whereas in normal glia it was low. Mino treatment increased GRP78 expression and reduced binding of GRP78 with protein kinase-like endoplasmic reticulum kinase. Subsequently, Mino increased eIF2α phosphorylation and CHOP expression. Knockdown of eIF2α or CHOP reduced Mino-induced LC3-II conversion and glioma cell death. When autophagy was inhibited, Mino induced cell death in a caspase-dependent manner. Rapamycin in combination with Mino produced synergistic effects on LC3 conversion, reduction of the Akt/mTOR/p70S6K pathway, and glioma cell death. Bioluminescent imaging showed that Mino inhibited the growth of glioma and prolonged survival time and that these effects were blocked by shCHOP.
  
  
  CONCLUSIONS
  Mino induced autophagy by eliciting endoplasmic reticulum stress response and switched cell death from autophagy to apoptosis when autophagy was blocked. These results coupled with clinical availability and a safe track record make Mino a promising agent for the treatment of malignant gliomas.
authors.affiliation: Institute of Basic Medical Sciences, Division of Neurosurgery, Department of Surgery, National Cheng-Kung University Hospital, Tainan, Taiwan.
authors.forename: Wei-Ting
authors.initials: WT
authors.lastname: Liu
authors.forename: Chih-Yuan
authors.initials: CY
authors.lastname: Huang
authors.forename: I-Chen
authors.initials: IC
authors.lastname: Lu
authors.forename: Po-Wu
authors.initials: PW
authors.lastname: Gean
mesh_terms: D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology* / Q000627:therapeutic use; D017209:Apoptosis / Q000187:drug effects*; D001343:Autophagy / Q000187:drug effects*; D001932:Brain Neoplasms / Q000188:drug therapy* / Q000378:metabolism; D002460:Cell Line; D000091342:Endoplasmic Reticulum Chaperone BiP; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects*; D015852:Eukaryotic Initiation Factor-2 / Q000378:metabolism; D005910:Glioma / Q000188:drug therapy* / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000378:metabolism; D006801:Humans; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D008911:Minocycline / Q000494:pharmacology* / Q000627:therapeutic use; D051381:Rats; D015398:Signal Transduction; D051742:Transcription Factor CHOP / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D000091342:Endoplasmic Reticulum Chaperone BiP; D015852:Eukaryotic Initiation Factor-2; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; C000717248:Hspa5 protein, mouse; D008869:Microtubule-Associated Proteins; D051742:Transcription Factor CHOP; D008911:Minocycline
keywords: ER stress; apoptosis; autophagy; glioma; minocycline