Expressions and clinical significance of cyclooxygenase-2 and p16 in gastric cancer and its precancerous lesions

Background: Monitoring gastric precancerous lesions is the key point for the prevention and early diagnosis of gastric cancer. Aims: To investigate the expressions of cyclooxygenase-2 (COX-2) and p16 in gastric cancer and its precancerous lesions, and to appraise the significance for the early diagnosis of gastric cancer. Methods: Expressions of COX-2 and p16 in tissues of 20 normal gastric mucosa, 60 intestinal metaplasia, 60 gastric intraepithelial neoplasia and 60 gastric cancer were determined by immunohistochemical staining, and the relationship between the two parameters was analyzed. Results: Expression of COX-2 was increased whereas expression of p16 was decreased stepwisely with the progression of gastric lesions, in the order of normal gastric mucosa, intestinal metaplasia, intraepithelial neoplasia and cancer. The positive expression rates of COX-2 and p16 in high-grade intraepithelial neoplasia, early and advanced gastric cancer were significantly different from those in normal gastric mucosa and intestinal metaplasia (P<0.05), whereas no significance difference was found between either the former three or the latter two. The positive expression rates of COX-2 and p16 were not statistically different between small intestinal metaplasia, complete and incomplete colonic metaplasia, between early and advanced gastric cancer, while statistically significant difference was found between low-grade and high-grade intraepithelial neoplasia (P<0.05). There was a negative correlation between the expression of COX-2 and that of p16 (P<0.001). The percentage of patients with positive expression of COX-2 accompanied by negative expression of p16 in early gastric cancer was significantly more than that in high-grade intraepithelial neoplasia (P<0.05). Conclusions: The detection of COX-2, p16 or the two combined is useful for the monitoring and follow-up of gastric precancerous lesions, as well as for the screening of high-risk population of gastric cancer, which may provide an important detection method for the early diagnosis of gastric cancer.