title: Xenin-immunoreactive cells and extractable xenin in neuroendocrine tumors of duodenal origin.
abstract: OBJECTIVE
  Xenin is a 25-amino acid peptide produced by specific endocrine cells of the duodenal mucosa. We investigated whether xenin is expressed in neuroendocrine tumors.
  
  
  METHODS
  Seventy-two foregut and midgut neuroendocrine tumors were examined by means of immunohistochemistry, confocal laser microscopy with an antibody against the C-terminus of xenin, and high-pressure liquid chromatography after acidic extraction, assessed by radioimmunoassay.
  
  
  RESULTS
  We found xenin-immunoreactive cells in 23 of 26 duodenal neuroendocrine tumors, including gastrinomas, somatostatinomas, and nonfunctioning and enterochromaffin cell tumors. In these tumors, up to 20% of the endocrine cells were xenin immunoreactive, and xenin immunoreactivity was concentrated in secretory granules. Xenin was coexpressed with chromogranin A. We found no xenin expression in gastrin-, somatostatin-, and serotonin-immunoreactive cells. High-pressure liquid chromatography after acidic extraction revealed 497 +/- 285 pmol of xenin per gram of tissue in 5 duodenal gastrinomas. The other neuroendocrine tumors, such as bronchial carcinoids, gastric enterochromaffin-like cell carcinoids, gastric and ileal enterochromaffin cell carcinoids, insulinomas, and gastrinomas of pancreatic origin, did not contain immunoreactive xenin.
  
  
  CONCLUSIONS
  Xenin is a peptide marker specific to neuroendocrine tumors of the duodenum. This finding may be useful in tumor classification and in the differential diagnosis of neuroendocrine tumors of the upper gut.
authors.affiliation: DRK-Krankenhaus Neuwied, Philipps Universität Marburg, Germany. g.feurle@uni-bonn.de
authors.forename: Gerhard E
authors.initials: GE
authors.lastname: Feurle
authors.forename: Martin
authors.initials: M
authors.lastname: Anlauf
authors.forename: Gerd
authors.initials: G
authors.lastname: Hamscher
authors.forename: Rudolf
authors.initials: R
authors.lastname: Arnold
authors.forename: Günter
authors.initials: G
authors.lastname: Klöppel
authors.forename: Eberhard
authors.initials: E
authors.lastname: Weihe
mesh_terms: D002851:Chromatography, High Pressure Liquid; D004379:Duodenal Neoplasms / Q000378:metabolism*; D015408:Gastrinoma / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D018358:Neuroendocrine Tumors / Q000378:metabolism*; D009496:Neurotensin; D010455:Peptides / Q000302:isolation & purification / Q000378:metabolism*; D013005:Somatostatinoma / Q000378:metabolism
chemical_list: D010455:Peptides; C077659:xenin 25; D009496:Neurotensin