Immunohistochemical analysis of COX-2 expression in dentigerous cyst, keratocystic odontogenic tumor and ameloblastoma: A comparative study

BACKGROUND: Cyclo-oxygenase-2 (COX-2) is an early response gene that is induced by growth factors, oncogenes and carcinogens and its expression is increased in various tumors. Increased expression of COX-2 plays a significant role in the development and growth of tumors by interfering in biological processes such as cell division, cellular immunity, cell adhesion, apoptosis, and angiogenesis. This study aimed to investigate the immunohistochemical expression of COX-2 in keratocystic odontogenic tumor (KOT) in comparison with ameloblastoma and dentigerous cyst with regards to different clinical behavior and histopathological features of these lesions. MATERIALS AND METHODS: Paraffined blocks of 45 cases including 15 cases of dentigerous cyst, 15 cases of KOT and 15 cases of ameloblastoma were stained with immunohistochemical method for COX-2. Five high-power fields of each sample were evaluated to determine the percentage of stained cells and the intensity of staining. Degree of immunoreactivity was obtained from the sum of two. Statistical evaluation was performed by the Kruskal-Wallis and ANOVA Mann-Whitney test (P < 0.05). RESULTS: Overexpression of COX-2 in ameloblastoma and KOT was observed compared with dentigerous cyst (P < 0.001). However, no significant difference was observed between the expression of COX-2 in ameloblastoma and KOT (P = 0.148). CONCLUSION: The COX-2 expression in odontogenic tumors such as ameloblastoma and cystic neoplasm with aggressive behavior such as KOT increases. However, it does not seem that COX-2 affects the development and growth of cysts with noninvasive behavior like dentigerous cyst.