Xenin-immunoreactive cells and extractable xenin in neuroendocrine tumors of duodenal origin.
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.
Feurle
Gerhard E
GE
DRK-Krankenhaus Neuwied, Philipps Universität Marburg, Germany. g.feurle@uni-bonn.de
Anlauf
Martin
M
Hamscher
Gerd
G
Arnold
Rudolf
R
Klöppel
Günter
G
Weihe
Eberhard
E
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
D010455:Peptides; C077659:xenin 25; D009496:Neurotensin