Alterations of the apc gene in carcinoma cell-lines and precancerous lesions of the stomach

Helicobacter pylori and telomerase activity in intestinal metaplasia of the stomach

BACKGROUND

Helicobacter pylori (H. pylori) has been considered a definitive carcinogen in gastric cancer. Telomerase is activated in gastric cancer and some premalignant gastric lesions, including intestinal metaplasia (IM). In this study, we evaluated the relationships of both H. pylori infection and telomerase activity with endoscopic and histologic features in IM. The effects of H. pylori eradication on endoscopic, histologic and biochemical changes were evaluated.

METHODS

Endoscopic biopsies were obtained from 43 patients with IM for rapid urease, histologic and telomerase tests. The endoscopic and histologic features, H. pylori infection and telomerase were assessed. After H. pylori eradication, 15 patients were re-evaluated and compared after 4 months.

RESULTS

Thirty-four (79.1%) patients were infected with H. pylori. The incidence of H. pylori infection was borderline correlated to the severity of IM (p = 0.076). Telomerase was elevated in eight (18.6%) patients. Telomerase tends to be high in subtype III and endoscopic grade III of IM. After H. pylori eradication, endoscopic extent (p = 0.039) and histologic severity (p = 0.074) showed improvements, and telomerase decreased significantly (p = 0.0001).

CONCLUSION

Our data suggest that telomerase is associated with the severity and extent of IM and that H. pylori eradication improves the endoscopic and histologic features in IM, and decreases telomerase activity. H. pylori eradication can be considered one of the methods to prevent gastric cancer in patients with H. pylori-infected IM. Further long-term and large-scaled study will be needed.

Inverse relationship between APC gene mutation in gastric adenomas and development of adenocarcinoma

Gastric cancer is common among the world, but genetic mechanisms of gastric carcinogenesis are not well understood. Gastric polypoid adenomas and flat dysplasias are regarded as precursor lesions. However, a detailed molecular study of these lesions has not been done to determine their role as precancerous lesions. We investigated mutations of the APC, beta-catenin, and K-ras genes, and microsatellite instability (MSI) status in 35 adenomas and 47 flat dysplasias without adenocarcinoma, 35 adenomas/dysplasias associated with adenocarcinomas, and 39 adenocarcinomas (20 diffuse type and 19 intestinal type). Somatic APC gene mutations were identified in 76% (59 of 78) of adenomas or flat dysplasias without associated adenocarcinoma, but in only 3% (1 of 30) of adenomas/dysplasias associated with adenocarcinoma, and in only 4% (3 of 69) of adenocarcinomas (P < 0.000001). No mutations of beta-catenin were found in adenocarcinomas, or adenomas/dysplasia without APC mutation. K-ras mutations were detected in 5% (4 of 82) of gastric adenomas/dysplasia without carcinoma, 3% (1 of 39) of adenocarcinomas without associated adenoma/dysplasia, and not in 32 adenocarcinomas with associated adenoma/dysplasia. High level of MSI (MSI-H) was more frequent in gastric adenoma/dysplasia associated with carcinoma (17%, 6 of 35) than in adenomas/dysplasia without carcinoma (3%, 2 of 75; P = 0.01). MSI-H was also more frequent in intestinal type adenocarcinoma (20%, 11 of 54) than in diffuse type (0%, 0 of 20; P = 0.03). APC gene mutations were present in six of nine (67%) of gastric adenomas/dysplasias with low level of MSI, but in none of the eight adenomas/dysplasia with MSI-H phenotype (P = 0.009). Our results indicate that somatic mutation of the APC gene plays an important role in the pathogenesis of gastric adenoma and dysplasia but has a limited role in neoplastic progression to adenocarcinoma. Gastric adenomas or dysplasias without APC mutations but with or without MSI may have a different biological behavior, and are precursors of intestinal-type of gastric adenocarcinomas.