title: Proteasome inhibitor interacts synergistically with autophagy inhibitor to suppress proliferation and induce apoptosis in hepatocellular carcinoma.
abstract: BACKGROUND
  The ubiquitin-proteasome system and autophagy-lysosome system are 2 major protein degradation pathways in eukaryotic cells, which are tightly linked to cancer. Proteasome inhibitors have been approved in clinical use against hematologic malignancies, but their application in solid tumors is uncertain. Moreover, the role of autophagy after proteasome inhibition is controversial.
  
  
  METHODS
  Two proteasome inhibitors, 2 autophagy inhibitors, and 3 hepatocellular carcinoma (HCC) cell lines were investigated in the current study. In vitro, cell proliferation was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, cell apoptosis was evaluated by flow cytometry analysis of annexin-V/propidium iodide staining, and autophagy was evaluated by green fluorescent protein-light chain 3 (GFP-LC3) redistribution and LC3 Western blot analysis. In vivo, Ki-67 staining was used to detect cell proliferation, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL) staining was used to detect apoptosis, and electron microscopy and p62 immunohistochemical staining were used to detect autophagy.
  
  
  RESULTS
  Proteasome inhibitors suppressed proliferation, induced apoptosis, and activated autophagy in HCC cell lines in vitro, and autophagy exerted a protective role after proteasome inhibition. In vivo, anticancer effects of bortezomib on the MHCC-97H orthotopic model (human HCC cells) were different from the effects observed on the Huh-7 subcutaneous model (human HCC cells). The autophagy inhibitor chloroquine interacted synergistically with bortezomib to suppress proliferation and induce apoptosis in both tumor models.
  
  
  CONCLUSIONS
  The current results indicated that simultaneous targeting of the proteasome and autophagy pathways may represent a promising method for HCC treatment.
authors.affiliation: Department of Liver Surgery, Liver Cancer Institute, Zhongshan Hospital, Fudan University, Shanghai, China.
authors.forename: Bo
authors.initials: B
authors.lastname: Hui
authors.forename: Ying-Hong
authors.initials: YH
authors.lastname: Shi
authors.forename: Zhen-Bin
authors.initials: ZB
authors.lastname: Ding
authors.forename: Jian
authors.initials: J
authors.lastname: Zhou
authors.forename: Cheng-Yu
authors.initials: CY
authors.lastname: Gu
authors.forename: Yuan-Fei
authors.initials: YF
authors.lastname: Peng
authors.forename: Hua
authors.initials: H
authors.lastname: Yang
authors.forename: Wei-Ren
authors.initials: WR
authors.lastname: Liu
authors.forename: Guo-Ming
authors.initials: GM
authors.lastname: Shi
authors.forename: Jia
authors.initials: J
authors.lastname: Fan
mesh_terms: D000225:Adenine / Q000031:analogs & derivatives / Q000494:pharmacology; D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D000970:Antineoplastic Agents / Q000494:pharmacology; D017209:Apoptosis; D051017:Apoptosis Regulatory Proteins / Q000378:metabolism; D001343:Autophagy / Q000187:drug effects; D000071186:Beclin-1; D001897:Boronic Acids / Q000494:pharmacology; D000069286:Bortezomib; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy* / Q000473:pathology*; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects*; D002738:Chloroquine / Q000494:pharmacology; D015853:Cysteine Proteinase Inhibitors / Q000494:pharmacology; D006801:Humans; D007976:Leupeptins / Q000494:pharmacology; D008565:Membrane Proteins / Q000378:metabolism; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism; D061988:Proteasome Inhibitors / Q000494:pharmacology*; D011719:Pyrazines / Q000494:pharmacology
chemical_list: D000590:Amino Acid Chloromethyl Ketones; D000970:Antineoplastic Agents; D051017:Apoptosis Regulatory Proteins; C491997:BECN1 protein, human; D000071186:Beclin-1; D001897:Boronic Acids; D015853:Cysteine Proteinase Inhibitors; D007976:Leupeptins; C477012:MAP1LC3A protein, human; D008565:Membrane Proteins; D008869:Microtubule-Associated Proteins; D061988:Proteasome Inhibitors; D011719:Pyrazines; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; C025946:3-methyladenine; D000069286:Bortezomib; D002738:Chloroquine; D046988:Proteasome Endopeptidase Complex; D000225:Adenine; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde