title: Time-dependent effect of hypoxia on tumor progression and liver progenitor cell markers in primary liver tumors.
abstract: OBJECTIVE
  Expression of liver progenitor cell (LPC) characteristics has been proposed as a negative prognostic marker in primary liver tumors. Hypoxia has been linked to activation of the Notch pathway which is responsible for activation and proliferation of LPCs and hypoxia-induced LPC activation has been shown in hepatocellular carcinoma. Our aim was to elucidate the time-dependent effects of hypoxia on the LPC niche in hepatocellular carcinoma which could aid in determining a safe time frame for use of hypoxia inducing therapies.
  
  
  METHODS
  We used dimethyloxaloylglycine to mimic a hypoxic reaction in mice by stabilizing hypoxia-inducible factor 1 alpha at three distinct time points in diethylnitrosamine induced hepatocarcinogenesis. LPC, metastasis and Notch pathway markers were determined by quantitative PCR and (immune)histochemistry (heamatoxillin-eosin, reticulin, Sirius red and cytokeratin 19 staining).
  
  
  RESULTS
  Activating the hypoxia inducible pathway early in hepatocarcinogenesis resulted in an increased incidence of both cholangioma and hepatocellular lesions, associated with high expression of LPC, metastatic and Notch pathway markers. Adversely, activating the hypoxic response during tumor development resulted in decreased incidence of hepatocellular lesions and increased cholangioma incidence, with an unaltered gene expression profile of LPC-, Notch pathway- and metastatic markers. A hypoxic insult at advanced stages of hepatocarcinogenesis severely increased the expression of LPC characteristics, however without increased expression of actors of the Notch pathway and metastatic markers and minor changes in incidence of hepatocellular and cholangioma lesions.
  
  
  CONCLUSIONS
  Our results indicate that increased hypoxia at the onset of tumor development has detrimental effects on tumor progression; patients with HCC developed in a background of fibrosis/cirrhosis might therefore represent a more difficult treatment group. In contrast, hypoxia during tumor development appears to favor tumor outcome, highlighting the importance of early detection. Finally, hypoxia in advanced stages resulted in increased expression of LPC characteristics indicating poor outcome.
authors: Gastro-enterology and hepatology, Ghent University, Ghent, Belgium.
authors: Eliene
authors: E
authors: Bogaerts
authors: Department of Medical Biochemistry and Microbiology, Uppsala University, Uppsala, Sweden.
authors: Femke
authors: F
authors: Heindryckx
authors: Gastro-enterology and hepatology, Ghent University, Ghent, Belgium.
authors: Lindsey
authors: L
authors: Devisscher
authors: Gastro-enterology and hepatology, Ghent University, Ghent, Belgium.
authors: Annelies
authors: A
authors: Paridaens
authors: Gastro-enterology and hepatology, Ghent University, Ghent, Belgium.
authors: Yves-Paul
authors: YP
authors: Vandewynckel
authors: Gastro-enterology and hepatology, Ghent University, Ghent, Belgium.
authors: Anja
authors: A
authors: Van den Bussche
authors: Gastro-enterology and hepatology, Ghent University, Ghent, Belgium.
authors: Xavier
authors: X
authors: Verhelst
authors: Department of Pathology, University Hospital Ghent, Ghent, Belgium.
authors: Louis
authors: L
authors: Libbrecht
authors: Liver Cell Biology Lab, Vrije universiteit Brussel, Brussels, Belgium.
authors: Leo A
authors: LA
authors: van Grunsven
authors: Gastro-enterology and hepatology, Ghent University, Ghent, Belgium.
authors: Anja
authors: A
authors: Geerts
authors: Gastro-enterology and hepatology, Ghent University, Ghent, Belgium.
authors: Hans
authors: H
authors: Van Vlierberghe
mesh_terms: D000818:Animals; D000951:Antigens, Neoplasm / Q000378:metabolism; D015415:Biomarkers; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D015815:Cell Adhesion Molecules / Q000378:metabolism; D002471:Cell Transformation, Neoplastic / Q000139:chemically induced / Q000235:genetics / Q000378:metabolism; D004195:Disease Models, Animal; D018450:Disease Progression; D000071858:Epithelial Cell Adhesion Molecule; D015870:Gene Expression; D000860:Hypoxia / Q000378:metabolism*; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000235:genetics / Q000378:metabolism; D007150:Immunohistochemistry; D053539:Keratin-19 / Q000378:metabolism; D008113:Liver Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology*; D008297:Male; D051379:Mice; D009362:Neoplasm Metastasis; D012333:RNA, Messenger / Q000235:genetics; D051880:Receptors, Notch / Q000378:metabolism; D013234:Stem Cells / Q000378:metabolism*; D013997:Time Factors
chemical_list: D000951:Antigens, Neoplasm; D015415:Biomarkers; D015815:Cell Adhesion Molecules; D000071858:Epithelial Cell Adhesion Molecule; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D053539:Keratin-19; D012333:RNA, Messenger; D051880:Receptors, Notch