title: Melatonin, a novel selective ATF-6 inhibitor, induces human hepatoma cell apoptosis through COX-2 downregulation.
abstract: OBJECTIVE
  To clarify the mechanisms involved in the critical endoplasmic reticulum (ER) stress initiating unfolded protein response pathway modified by melatonin.
  
  
  METHODS
  Hepatoma cells, HepG2, were culturedin vitro. Flow cytometry and TUNEL assay were used to measure HepG2 cell apoptosis. Western blotting and quantitative reverse transcription-polymerase chain reaction methods were used to determine the protein and messenger RNA levels of ER stress and apoptosis related genes' expression, respectively. Tissue microarray construction from patients was verified by immunohistochemical analysis.
  
  
  RESULTS
  In the present study, we first identified that melatonin selectively blocked activating transcription factor 6 (ATF-6) and then inhibited cyclooxygenase-2 (COX-2) expression, leading to enhanced liver cancer cell apoptosis under ER stress condition. Dramatically increased CCAAT-enhancer-binding protein homologous protein level, suppressed COX-2 and decreased Bcl-2/Bax ratio by melatonin or ATF-6 siRNA contributed the enhanced HepG2 cell apoptosis under tunicamycin (an ER stress inducer) stimulation. In clinical hepatocellular carcinoma patients, the close relationship between ATF-6 and COX-2 was further confirmed.
  
  
  CONCLUSIONS
  These findings indicate that melatonin as a novel selective ATF-6 inhibitor can sensitize human hepatoma cells to ER stress inducing apoptosis.
authors.affiliation: Li-Jia Bu, Han-Qing Yu, Lu-Lu Fan, Xiao-Qiu Li, Fang Wang, Jia-Tao Liu, Fei Zhong, Cong-Jun Zhang, Hua Wang, Guo-Ping Sun, Department of Oncology, the First Affiliated Hospital of Anhui Medical University, Hefei 230022, Anhui Province, China.
authors.forename: Li-Jia
authors.initials: LJ
authors.lastname: Bu
authors.affiliation: Li-Jia Bu, Han-Qing Yu, Lu-Lu Fan, Xiao-Qiu Li, Fang Wang, Jia-Tao Liu, Fei Zhong, Cong-Jun Zhang, Hua Wang, Guo-Ping Sun, Department of Oncology, the First Affiliated Hospital of Anhui Medical University, Hefei 230022, Anhui Province, China.
authors.forename: Han-Qing
authors.initials: HQ
authors.lastname: Yu
authors.affiliation: Li-Jia Bu, Han-Qing Yu, Lu-Lu Fan, Xiao-Qiu Li, Fang Wang, Jia-Tao Liu, Fei Zhong, Cong-Jun Zhang, Hua Wang, Guo-Ping Sun, Department of Oncology, the First Affiliated Hospital of Anhui Medical University, Hefei 230022, Anhui Province, China.
authors.forename: Lu-Lu
authors.initials: LL
authors.lastname: Fan
authors.affiliation: Li-Jia Bu, Han-Qing Yu, Lu-Lu Fan, Xiao-Qiu Li, Fang Wang, Jia-Tao Liu, Fei Zhong, Cong-Jun Zhang, Hua Wang, Guo-Ping Sun, Department of Oncology, the First Affiliated Hospital of Anhui Medical University, Hefei 230022, Anhui Province, China.
authors.forename: Xiao-Qiu
authors.initials: XQ
authors.lastname: Li
authors.affiliation: Li-Jia Bu, Han-Qing Yu, Lu-Lu Fan, Xiao-Qiu Li, Fang Wang, Jia-Tao Liu, Fei Zhong, Cong-Jun Zhang, Hua Wang, Guo-Ping Sun, Department of Oncology, the First Affiliated Hospital of Anhui Medical University, Hefei 230022, Anhui Province, China.
authors.forename: Fang
authors.initials: F
authors.lastname: Wang
authors.affiliation: Li-Jia Bu, Han-Qing Yu, Lu-Lu Fan, Xiao-Qiu Li, Fang Wang, Jia-Tao Liu, Fei Zhong, Cong-Jun Zhang, Hua Wang, Guo-Ping Sun, Department of Oncology, the First Affiliated Hospital of Anhui Medical University, Hefei 230022, Anhui Province, China.
authors.forename: Jia-Tao
authors.initials: JT
authors.lastname: Liu
authors.affiliation: Li-Jia Bu, Han-Qing Yu, Lu-Lu Fan, Xiao-Qiu Li, Fang Wang, Jia-Tao Liu, Fei Zhong, Cong-Jun Zhang, Hua Wang, Guo-Ping Sun, Department of Oncology, the First Affiliated Hospital of Anhui Medical University, Hefei 230022, Anhui Province, China.
authors.forename: Fei
authors.initials: F
authors.lastname: Zhong
authors.affiliation: Li-Jia Bu, Han-Qing Yu, Lu-Lu Fan, Xiao-Qiu Li, Fang Wang, Jia-Tao Liu, Fei Zhong, Cong-Jun Zhang, Hua Wang, Guo-Ping Sun, Department of Oncology, the First Affiliated Hospital of Anhui Medical University, Hefei 230022, Anhui Province, China.
authors.forename: Cong-Jun
authors.initials: CJ
authors.lastname: Zhang
authors.affiliation: Li-Jia Bu, Han-Qing Yu, Lu-Lu Fan, Xiao-Qiu Li, Fang Wang, Jia-Tao Liu, Fei Zhong, Cong-Jun Zhang, Hua Wang, Guo-Ping Sun, Department of Oncology, the First Affiliated Hospital of Anhui Medical University, Hefei 230022, Anhui Province, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Wei
authors.affiliation: Li-Jia Bu, Han-Qing Yu, Lu-Lu Fan, Xiao-Qiu Li, Fang Wang, Jia-Tao Liu, Fei Zhong, Cong-Jun Zhang, Hua Wang, Guo-Ping Sun, Department of Oncology, the First Affiliated Hospital of Anhui Medical University, Hefei 230022, Anhui Province, China.
authors.forename: Hua
authors.initials: H
authors.lastname: Wang
authors.affiliation: Li-Jia Bu, Han-Qing Yu, Lu-Lu Fan, Xiao-Qiu Li, Fang Wang, Jia-Tao Liu, Fei Zhong, Cong-Jun Zhang, Hua Wang, Guo-Ping Sun, Department of Oncology, the First Affiliated Hospital of Anhui Medical University, Hefei 230022, Anhui Province, China.
authors.forename: Guo-Ping
authors.initials: GP
authors.lastname: Sun
mesh_terms: D051702:Activating Transcription Factor 6 / Q000037:antagonists & inhibitors* / Q000235:genetics; D000975:Antioxidants / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects*; D022762:CCAAT-Enhancer-Binding Proteins / Q000378:metabolism*; D051546:Cyclooxygenase 2 / Q000378:metabolism*; D015536:Down-Regulation; D059865:Endoplasmic Reticulum Stress / Q000187:drug effects*; D056945:Hep G2 Cells; D006801:Humans; D020287:In Situ Nick-End Labeling; D008113:Liver Neoplasms; D008550:Melatonin / Q000494:pharmacology*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000378:metabolism; D034622:RNA Interference; D012333:RNA, Messenger / Q000378:metabolism; D034741:RNA, Small Interfering; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D014415:Tunicamycin / Q000494:pharmacology; D056811:Unfolded Protein Response / Q000187:drug effects*; D051028:bcl-2-Associated X Protein / Q000378:metabolism
chemical_list: C497111:ATF6 protein, human; D051702:Activating Transcription Factor 6; D000975:Antioxidants; C494826:BAX protein, human; C000595707:BCL2 protein, human; D022762:CCAAT-Enhancer-Binding Proteins; D019253:Proto-Oncogene Proteins c-bcl-2; D012333:RNA, Messenger; D034741:RNA, Small Interfering; D051028:bcl-2-Associated X Protein; D014415:Tunicamycin; C070790:CEBPE protein, human; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D008550:Melatonin
keywords: Activating transcription factor 6; Cyclooxygenase-2; Endoplasmic reticulum stress; Hepatocellular carcinoma; Melatonin