Immunohistoc hemical localization of Inducible Nitric Oxide Synthase in Pleomorphic Adenoma of Salivary Gland: Correlation with Cyclooxygenase-2 and Tumor Proliferative Activity

Abstract

Objectives: to investigate immunohistochemically localization pattern and distribution ofinducible Nitric Oxide Synthase (iNOS) in pleomorphic adenoma (PA ) of salivary glands and tofind a correlation of its expression with Cyclooxygenase-2 (COX -2) and tumor proliferative activity.Material and Methods: 18 cases of PA were subjected to immunohistochemical stainingfor iNOS, COX-2 and proliferative cell nuclear antigen (PCNA) using streptavidin-peroxidasetechnique. 10 samples of normal salivary glands tissues (NSG) were used as a control. COX-2,iNOS and PCNA expression were statistically compared.Results: in PA , expression of iNOS was increased as that of COX-2 when compared withthe control. The expression intensity and pattern of distribution of studied proteins were differentwithin the tumor tissue. The strong expression was localized mainly at the tumor periphery whilethe center of tumor showed weak or even negative expression. The PCNA-LI mean percentage washigher in the periphery of the tumors. The low expression scores of iNOS were detected in 4 cases,moderate in 5 cases and high in 7 cases, whereas the expression scores of COX-2 were observed in5 cases (low), in 9 cases (moderate) and 5 cases (high). The expression scores of iNOs and COX-2were significantly correlated (P≤0.05). Significant correlation of expression scores of COX -2 andiNOS with PCNA-LI (P≤0.01) were found.Conclusion: this study revealed that COX -2 and iNOS expression was increased significantlyin PA . Their pattern of expression was more in the periphery of the lesion than the center. Thelabelling index of PCNA was higher in the periphery of the lesion indicating that the tumorousand proliferative activity of PA is more at tumor tissues near the margins suggesting that theaggressiveness of PA is at the tumor peripheries.