Immunohistochemical analysis of gastric carcinomas and matched normal mucosa showed that the mean staining intensity of COX-2 in H. pylori-positive gastric carcinoma was 2.26 ± 0.17, significantly higher than in H. pylori-negative gastric cancer tissues (0.63 ± 0.16, P < 0.01; Fig. 1a, b). Here, PTGS2 is linked to gastric cancer.