title: [Thioridazine Sensitizes Apoptotic Effect of TRAIL in Human Lung Cancer PC9 Cells Through ER Stress Mediated Up-regulation of DR5].
abstract: BACKGROUND
  Tumor necrosis factor-related apoptosis-inducting ligand (TRAIL) can induce apoptosis of tumor cells, however, various of tumor cells may survive because of resistance to TRAIL-mediated apoptosis. This study is to observe the proliferation inhibition effect of TRAIL sensitized by thioridazine on PC9 cells through endoplasmic reticulum (ER) stress mediated up-regulation of death receptor 5 (DR5) and investigate its mechanism.
  
  
  METHODS
  PC9 cells were treated with different concentrations of thioridazine and TRAIL alone or in combination. Cell proliferation was measured by MTT assay, and cell apoptosis and cell-surface DR5 were detected by flow cytometry. Western blotting was utilized to measure the expressions of ER stress-related proteins glucose regulated protein 78 (GRP78), C/EBP homologous protein (CHOP), p-PKR-like ER kinase (PERK), p-eukaryotic initiation factor-2α (eIF2α), activating transcription factor 4 (ATF4) and apoptosis-related proteins caspase-3, caspase-9, caspase-8, PARP, DR5.
  
  
  RESULTS
  Thioridazine inhibited the proliferation of PC9 cells in a dose-dependent manner (P<0.05). Thioridazine increased the inhibition and apoptosis of PC9 cells and up-regulated the expression of cell-surface DR5 induced by TRAIL. Flow cytometry showed that compared with TRAIL group, combination group of TRAIL and thioridazine increased cell apoptotic rates significantly (P<0.05). Western blotting indicated that compared with TRAIL group, expressions of Cleaved-caspase-8, Cleaved-PARP and DR5 increased significantly in combination group of TRAIL and thioridazine. The induction of DR5 and pro-apoptotic effect were mediated through activation of ER stress accompanying by increased synthesis of GRP78 and CHOP, which can be blocked by adding of ER stress inhibitor 4-PBA.
  
  
  CONCLUSIONS
  Thioridazine enhanced proliferation inhibition effect of TRAIL in PC9 cells may be facilitated through ER stress mediated upregulation of DR5. .
authors.affiliation: Department of Oncology, the Third Affiliated Hospital of Anhui Medical University, Hefei 230061, China.
authors.forename: Juan
authors.initials: J
authors.lastname: Li
authors.affiliation: Department of Oncology, the Third Affiliated Hospital of Anhui Medical University, Hefei 230061, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Oncology, the Third Affiliated Hospital of Anhui Medical University, Hefei 230061, China.
authors.forename: Liu
authors.initials: L
authors.lastname: Liu
authors.affiliation: Central Laboratory of Hefei Binhu Hospital, Hefei 230061, China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Yuan
authors.affiliation: Department of Oncology, the Third Affiliated Hospital of Anhui Medical University, Hefei 230061, China.
authors.forename: Yangyi
authors.initials: Y
authors.lastname: Bao
mesh_terms: D017209:Apoptosis / Q000187:drug effects*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D019008:Drug Resistance, Neoplasm / Q000187:drug effects; D004357:Drug Synergism; D000091342:Endoplasmic Reticulum Chaperone BiP; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects*; D006801:Humans; D008175:Lung Neoplasms / Q000473:pathology*; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand / Q000378:metabolism*; D053221:TNF-Related Apoptosis-Inducing Ligand / Q000494:pharmacology*; D013881:Thioridazine / Q000494:pharmacology*; D015854:Up-Regulation / Q000187:drug effects*
chemical_list: D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; D053220:Receptors, TNF-Related Apoptosis-Inducing Ligand; D053221:TNF-Related Apoptosis-Inducing Ligand; C505639:TNFRSF10B protein, human; D013881:Thioridazine