Immunohistochemical evidence for an impairment of autophagy in tumorigenesis of gastric carcinoids and adenocarcinomas in rodent models and patients.

BACKGROUND/AIM: Autophagy has dual roles in tumorigenesis: tumor-promoting or tumor-suppressing. The aim of the present study was to examine autophagy-related markers by immunohistochemistry in gastric carcinoids and adenocarcinomas in rodent models and patients. METHODS: Gastric carcinoids in Mastomys were induced by loxtidine treatment. Spontaneously developed gastric adenocarcinomas in Japanese cotton rats and INS-GAS transgenic mice were included. Patient tissue samples of gastric carcinoids or adenocarcinomas were collected. Immunohistochemistry was performed against autophagy-related gene protein-6 (ATG-6, also called beclin-1), ATG-5 and ATG-16. RESULTS: In tumor-free Mastomys, ATG-5, ATG-16 and beclin-1 were immunepositive in the gastric mucosa. In tumor-bearing Mastomys, ATG-5 and ATG-16 were negative in the tumors, whereas beclin-1 was positive in four of five animals. In carcinoid patients, ATG-5 was negative in six of ten, ATG-16 negative in nine of ten, and beclin-1 negative in three of ten patients. In cotton rats, ATG-5 and ATG-16 were negative in all tumors. Beclin-1 was negative in three of five rats. In INS-GAS mice, ATG-5 and beclin-1 were positive in the tumor area, but the numbers of immunopositive cells per gland were reduced by about 50% in comparison with wild-type mice. In adenocarcinoma patients, ATG-5 and ATG-16 were negative in eight of ten, and beclin-1 positive in all ten patients. CONCLUSIONS: An impaired autophagy took place at the stage of formation of ATG-5-ATG-12-ATG-16 complex in both gastric carcinoids and adenocarcinoma of both rodent models and patients. ATG-5 and ATG-16 might be better markers than beclin-1 in assessing autophagy in these lesions.

Ultrastructure of ECL cells in Mastomys after long-term treatment with H2 receptor antagonist loxtidine.

Gastric ECL-cell hyperplasia and carcinoids (ECLoma) develop after 1 year in rats treated with omeprazole or 2 months in Mastomys treated with loxtidine. The aim of this study was to examine the ultrastructure of ECL cells in Mastomys after loxtidine treatment with an attempt to evaluate whether an impairment of autophagy was involved in the tumorigenesis. Mastomys were given loxtidine for 8 or 27 weeks. Morphological analysis of ECL cells showed that (1) cell size was not increased after 8 or 27 weeks; (2) secretory vesicles, a hallmark feature of welldifferentiated ECL cells, were unchanged after 8 weeks but reduced after 27 weeks; (3) granules were reduced after 8 or 27 weeks; (4) microvesicles were unchanged after the treatment; and (5) vacuoles and lipofuscin bodies were found occasionally after 8 weeks but not at 27 weeks. In addition, the appearance of ECL-cell ultrastructure differed between loxtidine-treated Mastomys and rats treated with omeprazole or subjected to antrectomy, but was similar between Mastomys treated with loxtidine for 27 weeks and mice deficient in CCK(2) receptor. We suggest that the ultrastructure of ECL cells in Mastomys after long-term treatment with loxtidine displayed an impaired formation of vacuoles and lipofuscin bodies, markers of the autophagic pathway.

Experimental gastrocystoplasty in rats: risk of developing ECLoma.

OBJECTIVE: There are no clinical reports on the risk of carcinoids in the gastric segment following gastrocystoplasty. The aim of the present study was to examine whether gastric carcinoids could develop in a rat model of gastrocystoplasty. MATERIALS AND METHODS: Rats were subjected to gastrocystoplasty in which 10% of the oxyntic part of the stomach was removed (i.e. 10% fundectomy), gastrocystoplasty with 90% fundectomy (known to induce hypergastrinemia), sham operation, or no operation, and were followed up for 6 months. Tissue specimens of bladder and stomach were analyzed by means of pathology and immunohistochemistry. RESULTS: Atrophy of gastric glands in the augmented bladders was found after gastrocystoplasty with either 10% or 90% fundectomy. Gastrocystoplasty with 90% fundectomy resulted in hyperplasia of the oxyntic mucosa, enterochromaffin-like (ECL) cell hyperplasia and ECLoma in the remnant stomach, and atrophy of the oxyntic mucosa and ECLoma in the gastric segment of the bladder. CONCLUSIONS: ECLoma could develop in the gastric segment of the bladder after gastrocystoplasty, particularly in the setting of hypergastrinemia. The tumorigenesis of ECLoma seems to follow the same pathological pathway regardless of whether the oxyntic mucosa is located in the stomach or the bladder.

Acid secretion in urinary bladder of rats subjected to gastrocystoplasty.

Urinary bladder augmentation with a segment of the stomach, i.e., gastrocystoplasty, has been used to improve capacity and compliance in patients with bladder dysfunction. In the present study, rats were subjected to gastrocystoplasty (using the oxyntic segment) with or without fundectomy (removal of the oxyntic part of stomach), and the acid secretion in the augmented bladder was measured. In freely fed rats, the pH values were neutral and not significantly decreased in the rats subjected to gastrocystoplasty with or without fundectomy compared to controls (no operation or sham operation). In response to food intake after being fasted, the rats subjected to gastocystoplasty + fundectomy produced significant amounts of acid. Immunohistochemical examination revealed that the ECL cells and parietal cells seemed to be normal in rats with gastrocystoplasty alone, and that micronodules of ECL appeared to develop in rats with gastrocystoplasty + fundectomy. We suggest that the rats subjected to gastrocystoplasty + fundectomy are capable of producing acid secretion in the bladder, probably due to the secretagogue and trophic effects of gastrin on the ECL cells in the segment of the oxyntic mucosal segment of the bladder.