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

Abstract

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 signifi cant 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: Paraffi ned 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 fi elds 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 signifi cant 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.
Key Words: Ameloblastoma, cyclo-oxygenase-2, dentigerous cyst, immunohistochemistry,
keratocystic odontogenic tumor