title: Modulation of the unfolded protein response impedes tumor cell adaptation to proteotoxic stress: a PERK for hepatocellular carcinoma therapy.
abstract: BACKGROUND
  Functional disturbances of the endoplasmic reticulum (ER) lead to activation of the unfolded protein response (UPR), which is involved in the consecutive steps of carcinogenesis. In human hepatocellular carcinoma (HCC), the UPR is shown to be activated; however, little is known about the UPR kinetics and effects of UPR modulation in HCC.
  
  
  METHODS
  We sequentially monitored the UPR over time in an orthotopic mouse model for HCC and explored the effects of UPR modulation on cell viability and proliferation in vitro and in the mouse model.
  
  
  RESULTS
  The expression of ER-resident chaperones peaked during tumor initiation and increased further during tumor progression, predominantly within the nodules. A peak in Ire1 signaling was observed during tumor initiation. The Perk pathway was activated during tumor progression, and the proapoptotic target Chop was upregulated from week 5 and continued to rise, especially in the tumors. The Atf6 pathway was modestly activated only after tumor initiation. Consistent with the UPR activation, electron microscopy demonstrated ER expansion and reorganization in HCC cells in vivo. Strikingly, under ER stress or hypoxia, the Perk inhibitor and not the Ire1 inhibitor reduced cell viability and proliferation via escalating proteotoxic stress in vitro. Notably, the Perk inhibitor significantly decreased tumor burden in the mouse model.
  
  
  CONCLUSIONS
  We provide the first evaluation of the UPR dynamics in a long-term cancer model and identified a small molecule inhibitor of Perk as a promising strategy for HCC therapy.
authors.affiliation: Department of Hepatology and Gastroenterology, Ghent University, De Pintelaan 185, 1K12 IE, 9000 Ghent, Belgium.
authors.forename: Yves-Paul
authors.initials: YP
authors.lastname: Vandewynckel
authors.affiliation: Department of Hepatology and Gastroenterology, Ghent University, De Pintelaan 185, 1K12 IE, 9000 Ghent, Belgium.
authors.forename: Debby
authors.initials: D
authors.lastname: Laukens
authors.affiliation: Department of Hepatology and Gastroenterology, Ghent University, De Pintelaan 185, 1K12 IE, 9000 Ghent, Belgium.
authors.forename: Eliene
authors.initials: E
authors.lastname: Bogaerts
authors.affiliation: Department of Hepatology and Gastroenterology, Ghent University, De Pintelaan 185, 1K12 IE, 9000 Ghent, Belgium.
authors.forename: Annelies
authors.initials: A
authors.lastname: Paridaens
authors.affiliation: Department of Hepatology and Gastroenterology, Ghent University, De Pintelaan 185, 1K12 IE, 9000 Ghent, Belgium.
authors.forename: Anja
authors.initials: A
authors.lastname: Van den Bussche
authors.affiliation: Department of Hepatology and Gastroenterology, Ghent University, De Pintelaan 185, 1K12 IE, 9000 Ghent, Belgium.
authors.forename: Xavier
authors.initials: X
authors.lastname: Verhelst
authors.affiliation: Department of Hepatology and Gastroenterology, Ghent University, De Pintelaan 185, 1K12 IE, 9000 Ghent, Belgium.
authors.forename: Christophe
authors.initials: C
authors.lastname: Van Steenkiste
authors.affiliation: Infinity Imaging Lab, Ghent University, De Pintelaan 185, 9000 Ghent, Belgium.
authors.forename: Benedicte
authors.initials: B
authors.lastname: Descamps
authors.affiliation: Infinity Imaging Lab, Ghent University, De Pintelaan 185, 9000 Ghent, Belgium ; GROUP-ID Consortium, Ghent University Hospital, Ghent University, De Pintelaan 185, 9000 Ghent, Belgium.
authors.forename: Chris
authors.initials: C
authors.lastname: Vanhove
authors.affiliation: Department of Pathology, Ghent University, De Pintelaan 185, 9000 Ghent, Belgium.
authors.forename: Louis
authors.initials: L
authors.lastname: Libbrecht
authors.affiliation: GROUP-ID Consortium, Ghent University Hospital, Ghent University, De Pintelaan 185, 9000 Ghent, Belgium ; Unit Immunoregulation and Mucosal Immunology, VIB Inflammation Research Center, Technologiepark 927, 9052 Ghent, Belgium.
authors.forename: Riet
authors.initials: R
authors.lastname: De Rycke
authors.affiliation: GROUP-ID Consortium, Ghent University Hospital, Ghent University, De Pintelaan 185, 9000 Ghent, Belgium ; Unit Immunoregulation and Mucosal Immunology, VIB Inflammation Research Center, Technologiepark 927, 9052 Ghent, Belgium ; Department of Respiratory Medicine, Ghent University Hospital, Ghent University, De Pintelaan 185, 9000 Ghent, Belgium.
authors.forename: Bart N
authors.initials: BN
authors.lastname: Lambrecht
authors.affiliation: Department of Hepatology and Gastroenterology, Ghent University, De Pintelaan 185, 1K12 IE, 9000 Ghent, Belgium.
authors.forename: Anja
authors.initials: A
authors.lastname: Geerts
authors.affiliation: GROUP-ID Consortium, Ghent University Hospital, Ghent University, De Pintelaan 185, 9000 Ghent, Belgium ; Unit Immunoregulation and Mucosal Immunology, VIB Inflammation Research Center, Technologiepark 927, 9052 Ghent, Belgium ; Department of Respiratory Medicine, Ghent University Hospital, Ghent University, De Pintelaan 185, 9000 Ghent, Belgium.
authors.forename: Sophie
authors.initials: S
authors.lastname: Janssens
authors.affiliation: Department of Hepatology and Gastroenterology, Ghent University, De Pintelaan 185, 1K12 IE, 9000 Ghent, Belgium.
authors.forename: Hans
authors.initials: H
authors.lastname: Van Vlierberghe
mesh_terms: D051702:Activating Transcription Factor 6 / Q000235:genetics; D000222:Adaptation, Physiological / Q000187:drug effects; D000818:Animals; D006528:Carcinoma, Hepatocellular / Q000737:chemistry / Q000188:drug therapy / Q000378:metabolism* / Q000648:ultrastructure; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002471:Cell Transformation, Neoplastic / Q000378:metabolism*; D004721:Endoplasmic Reticulum; D000091342:Endoplasmic Reticulum Chaperone BiP; D050956:HSP40 Heat-Shock Proteins / Q000235:genetics; D006360:Heat-Shock Proteins / Q000235:genetics; D056945:Hep G2 Cells; D006801:Humans; D008114:Liver Neoplasms, Experimental / Q000737:chemistry / Q000188:drug therapy / Q000378:metabolism* / Q000648:ultrastructure; D008297:Male; D008562:Membrane Glycoproteins / Q000235:genetics; D008565:Membrane Proteins / Q000037:antagonists & inhibitors / Q000235:genetics; D051379:Mice; D018384:Oxidative Stress; D010766:Phosphorylation / Q000187:drug effects; D047428:Protein Kinase Inhibitors / Q000494:pharmacology* / Q000627:therapeutic use; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics; D012333:RNA, Messenger / Q000032:analysis; D015398:Signal Transduction; D051742:Transcription Factor CHOP / Q000032:analysis / Q000235:genetics; D014415:Tunicamycin / Q000494:pharmacology; D056811:Unfolded Protein Response / Q000187:drug effects; D019892:eIF-2 Kinase / Q000037:antagonists & inhibitors / Q000378:metabolism*
chemical_list: D051702:Activating Transcription Factor 6; D000091342:Endoplasmic Reticulum Chaperone BiP; D050956:HSP40 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D047428:Protein Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D012333:RNA, Messenger; D051742:Transcription Factor CHOP; D014415:Tunicamycin; D019892:eIF-2 Kinase; C497112:Atf6 protein, mouse; C500846:Dnajc3 protein, mouse; C053387:endoplasmin; C486556:Ern2 protein, mouse
keywords: Endoplasmic reticulum; HepG2 cells; Inositol-requiring enzyme-1; Liver neoplasm; PERK kinase; Stress