Gastrointestinal
tumors are highly ranked regarding tumoral mortality worldwide. The development and progression of gastrointestinal (GI) diseases go hand in hand with the changes of tight junctions (TJ).
Claudins (CLDN) are the main TJ
proteins, showing different expression by the different tissues, with the expressed CLDN profile being representative. I. We explored the changes of CLDN expression in
Barrett's esophagus and related
adenocarcinoma. CLDN2 and -3 expression in
Barrett's esophagus was higher than in normal foveolar epithelium.
Adenocarcinoma showed higher CLDN2 and -3 expression compared with normal and Barrett's epithelia. The similar CLDN expression profile of
Barrett's esophagus and
adenocarcinoma supports their sequential development. II. Gastric intestinal
metaplasia showed higher expression of CLDN2, -3 and -4 as compared with normal
antral foveolar mucosa.
Tumors of small and large bowels exhibited higher CLDN2 expression when compared with normal epithelia. Colorectal
adenoma and
adenocarcinoma could not be differentiated according to their CLDN profile. Intestinal metaplasias of
Barrett's esophagus and stomach show similar CLDN profile to small bowel epithelium. III. Studies on duodenal mucosa in
celiac disease in childhood demonstrated CLDN2 and -3 expression to be higher than in normal mucosa. The expression was significantly higher in the distal part of the duodenum samples. This and the serious histological findings suggest that the distal duodenum is more adequate for biopsy testing. IV. Beside the epithelial cells, mesenchymal
tumors express intercellular junctional
proteins. Expression of
claudins in
gastrointestinal stromal tumors (GIST) and other mesenchymal
neoplasia was also studied. The CLDN profile was found to be representative to the individual
tumor. GIST,
angiosarcoma,
hemangioma,
leiomyosarcoma and
leiomyoma showed expression of various CLDNs. CLDN2 was detected in all entities. CLDN1, however, was found positive in
leiomyosarcoma only.
Leiomyoma, on the other hand, expressed only CLDN2. GISTs and
leiomyosarcomas showed CLDN2, -3, -4, -5 and -7-expression. The angiogenic
tumors revealed CLDN2 and -5 expression. The similar CLDN profile observable in GIST and
leiomyosarcoma is suggestive of a histogenetic relationship. Smooth muscle and vessel
tumors of different dignity could also be separated from each other based on CLDN profile.