Immunohistochemical expression of cyclooxygenase-2 in oral lichen planus and normal oral mucosa

Abstract

Oral lichen planus (OLP) is a chronic inflammatory disease for which the pathogenesis is complex and not fully understood; autoimmunity has been suggested as a causative factor. World health organization (WHO) has classified OLP as a potentially malignant lesion. Cyclooxygenase-2 (COX-2) is an inducible key enzyme that generates prostanoids which play a critical role in inflammation, immunopathology; also considered as a malignant potential marker. The present study was conducted to analyze and compare epithelial COX-2 expression in OLP clinical subtypes and normal oral mucosa to evaluate its role in the pathophysiology of the disease process. This retrospective immunohistochemistry (IHC) study was performed on tissue sections of 30 OLP and 10 normal oral mucosae for COX-2 expression. Descriptive and comparative statistical methods were done using 'one-way Analysis of Variance (ANOVA), 't' and Chi-square tests. All the OLP showed epithelial COX-2 expression; strong expression was noted in 80% of the OLP while normal oral mucosa sections showed no expression. Cox-2 expression was significantly higher in erosive lichen planus compared to reticular lichen planus. Strong expression of COX-2 in OLP suggested its important role in pathogenesis. Although COX-2 has been connected to malignant development and autoimmunity, as the malignant development in OLP is quite rare, this study suggests that increased levels of COX-2 seen here may support an autoimmune cause of the disease process.