title: Quantitative assessment of the cell surface proteome to identify novel therapeutic targets in cholangiocarcinoma.
abstract: BACKGROUND
  Cholangiocarcinoma has a high mortality and morbidity. Median survival is less than 6 months. Surgical resection is appropriate in certain circumstances. Because distal cholangiocarcinoma is difficult to distinguish from pancreatic cancers, patients might not receive optimum therapy. Proteomics is the study of complex cellular proteins using mass spectrometry. The aim of this study was to determine the constituent proteins on the cell surface of a model of cholangiocarcinoma.
  
  
  METHODS
  A sample preparation technique to enrich for cell surface proteins of the intrahepatic cholangiocarcinoma cell line CC-SW-1 was developed by modifying a NeutrAvidin-biotin system. After isolation, trypsin digestion, and purification, peptides were fractionated for tandem mass spectrometry before being analysed with the NCBInr database and the Mascot search algorithm. Results were confirmed by immunohistochemistry using a peroxidase detection technique on paraffin-embedded sections from resected specimens.
  
  
  RESULTS
  Peptide enrichment was confirmed by electrophoresis. 862 proteins were consistently expressed between samples (n=3). 271 of these proteins were attributed only to the cell surface. They included proteins used clinically for staging disease (cytokeratin 19 [CK19]), identifying cancer stem cells (epithelial cell adhesion molecule [EpCAM], neural cell adhesion molecule [NCAM], epithelial growth factor receptor [EGFR]), and indicating potential for differentiation (Frozzled receptor, Notch pathway). Novel markers from the tumour necrosis factor (TNF) receptor superfamily were also identified. Immunohistochemistry confirmed these findings.
  
  
  CONCLUSIONS
  The results from this surface proteomic profiling could help to identify novel therapeutic targets in cholangiocarcinoma. Further development of this technique could be translated to distinguish between distal cholangiocarcinoma and pancreatic cancers.
  
  
  BACKGROUND
  UK Medical Research Council.
authors: NIHR Biomedical Research Unit and Centre for Liver Research, University of Birmingham, Birmingham, UK. Electronic address: barneys@doctors.org.uk.
authors: Barney
authors: B
authors: Stephenson
authors: School of Cancer Sciences, University of Birmingham, Birmingham, UK.
authors: Neil
authors: N
authors: Shimwell
authors: NIHR Biomedical Research Unit and Centre for Liver Research, University of Birmingham, Birmingham, UK.
authors: Elizabeth
authors: E
authors: Humphreys
authors: Douglas Ward School of Cancer Sciences, University of Birmingham, Birmingham, UK.
authors: Douglas
authors: D
authors: Ward
authors: NIHR Biomedical Research Unit and Centre for Liver Research, University of Birmingham, Birmingham, UK.
authors: David
authors: D
authors: Adams
authors: School of Cancer Sciences, University of Birmingham, Birmingham, UK.
authors: Ashley
authors: A
authors: Martin
authors: NIHR Biomedical Research Unit and Centre for Liver Research, University of Birmingham, Birmingham, UK.
authors: Simon
authors: S
authors: Afford