title: Enhanced epidermal growth factor receptor activation in human cholangiocarcinoma cells.
abstract: OBJECTIVE
  Epidermal growth factor receptor (EGFR) signaling has been implicated in the genesis and progression of cholangiocarcinoma. However, the characteristics of EGFR signaling in cholangiocarcinoma cells have not been characterized. Thus, we attempted to more fully characterize EGF/EGFR signaling in human cholangiocarcinoma cells.
  
  
  METHODS
  EGFR phosphorylation and ubiquitination were evaluated using immunoblot techniques. EGFR internalization was analyzed by immunofluorescent staining of EGFR or by immunoblot analysis for biotinylated EGFR. Cell growth was assessed using the MTS assay.
  
  
  RESULTS
  EGFR activation was sustained following EGF stimulation in cholangiocarcinoma cells as compared to hepatoma cells. This prolonged EGFR activation resulted in extended p42/44 MAPK activation in cholangiocarcinoma cells. Despite ubiquitination, EGFR activation-dependent internalization was defective in cholangiocarcinoma cells. Cell growth was increased in cholangiocarcinoma cells following EGF stimulation as compared to hepatoma cells, and this was significantly attenuated by EGFR kinase inhibitors. The EGFR kinase inhibitors also significantly decreased COX-2 expression in cholangiocarcinoma cells, while this was not evident in hepatoma cells.
  
  
  CONCLUSIONS
  The results demonstrate that cholangiocarcinoma cells exhibit sustained EGFR activation due to defective receptor internalization. As EGFR kinase inhibitors effectively attenuated cellular growth, these agents may be therapeutically efficacious in human cholangiocarcinoma.
authors.affiliation: Department of Internal Medicine and Liver Research Institute, Seoul National University College of Medicine, Seoul 110-744, South Korea.
authors.forename: Jung-Hwan
authors.initials: JH
authors.lastname: Yoon
authors.forename: Geum-Youn
authors.initials: GY
authors.lastname: Gwak
authors.forename: Hyo-Suk
authors.initials: HS
authors.lastname: Lee
authors.forename: Steven F
authors.initials: SF
authors.lastname: Bronk
authors.forename: Nathan W
authors.initials: NW
authors.lastname: Werneburg
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Gores
mesh_terms: D001650:Bile Duct Neoplasms; D001653:Bile Ducts, Intrahepatic; D045744:Cell Line, Tumor; D018281:Cholangiocarcinoma; D051546:Cyclooxygenase 2; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066246:ErbB Receptors / Q000378:metabolism*; D000077156:Gefitinib; D006801:Humans; D008565:Membrane Proteins; D010766:Phosphorylation; D011451:Prostaglandin-Endoperoxide Synthases / Q000378:metabolism; D011799:Quinazolines / Q000494:pharmacology; D015398:Signal Transduction / Q000502:physiology; D020032:Tyrphostins / Q000494:pharmacology; D025801:Ubiquitin / Q000378:metabolism
chemical_list: D004791:Enzyme Inhibitors; D008565:Membrane Proteins; D011799:Quinazolines; D020032:Tyrphostins; D025801:Ubiquitin; C101044:RTKI cpd; D051546:Cyclooxygenase 2; C496540:PTGS2 protein, human; D011451:Prostaglandin-Endoperoxide Synthases; D066246:ErbB Receptors; D000077156:Gefitinib