Receptor autoradiographic evaluation of cholecystokinin, neurotensin, somatostatin and vasoactive intestinal peptide receptors in gastro-intestinal adenocarcinoma samples: Where are they really located?

Receptors for cholecystokinin (CCK), gastrin, neurotensin, somatostatin and vasoactive intestinal peptide (VIP) are over-expressed in several human tu mors, where they have diagnostic and therapeutic implications. Since report s on the expression of these peptide receptors in primary gastric and colon ic adenocarcinomas are either non-existent or conflicting, a detailed evalu ation with particular emphasis on the tissue localization was undertaken. C CK-A, CCK-B, neurotensin, somatostatin and VIP receptors were localized by in vitro receptor autoradiography with iodinated radioligands on histologic al sections of surgical samples of 27 gastric and 25 colonic adenocarcinoma s. CCK-A, CCK-B and neurotensin-l receptors were found in a minority of bot h tumor types. Somatostatin receptors were found in 18/27 gastric and 2/25 colonic cancers. VIP receptors were found in 14/26 gastric and 23/25 coloni c cancers; subtype characterization suggests VIPI receptors, In addition, r esected tumor samples contained non-malignant tissues (mucosa, smooth muscl e, nerves or vessels) with high amounts of the various peptide receptors, T herefore, regulatory peptide receptors are expressed differentially in gast ric and colonic cancers but also very frequently in "contaminating" non-mal ignant tissues. Since results using morphological techniques are superior t o those using homogenates, we recommend that localization of these receptor s to the tissues should always be attempted, to minimize receptor over-esti mation in tumors and to prevent spurious results. (C) 1999 Wiley-Liss, Inc.