Cyclooxygenase-2 expression and its relationship with proliferation of colorectal adenomas

BACKGROUND: Cyclooxygenase (COX)-2 may be linked to carcinogenesis. In the previous study, we examined COX-2 expression immunohistochemically in 95 adenomas and reported a significant correlation between its expression and the grade of dysplasia. To clarify the correlation between COX-2 expression and cell proliferation, we investigated Ki-67 labeling index using immunohistochemistry and its correlation with COX-2 expression. METHODS: Immunohistological staining for Ki-67 antigen was performed on 95 colorectal adenomas previously reported. RESULTS: The Ki-67 labeling index was significantly higher in the high-COX-2 group than in the low-COX-2 and negative groups in adenomas with moderate (44.5 +/- 6.4% vs 33.0 +/- 2.6%, 39.0 +/- 6.2%; P = 0.01, P < 0.001, respectively) or severe dysplasia (47.2 +/- 7.6% vs 40.3 +/- 7.2%, 35.0 +/- 5.4%; P = 0.02, P = 0.005, respectively). There was no correlation between Ki-67 labeling index and COX-2 expression in mild dysplasia. CONCLUSIONS: These results suggest that COX-2 may play a causal role in cell proliferation in carcinogenesis.