significance of nitric oxide synthase [NOS] and smooth muscle actin [SMA] immunoreactivity in pleomorphic adenoma

ABSTRACT

The actions of nitric oxide [NO] in the pathology of solid tumors are complicated and many arc poorly understood because NO has both inhibitory and tumor promoting activities. The aims of the present study were to find out immunohistochemically whether the expression of both the inducible [iNOS] and endothelial [eNOS] forms of the enzyme nitric oxide synthase [NOS] were changed in pleomorphic adenoma compared with normal salivary tissue and to determine whether or not the distribution of iNOS expression correlated with smooth muscle actin [SMA] expression. The results revealed that there was a highly significant difference in staining for iNOS between the tumor and normal salivary tissue, with tumor epithelial cells being stained in all studied cases [P < 0.0001]. The reaction for eNOS isoenzyme showed moderate staining of the tumor epithelium in only three cases. Salivary duct cells and the endothelium of blood vessels of normal salivary tissue showed moderate reactivity for eNOS. The distribution of SMA expression was in a similar manner to iNOS expression in normal salivary ducts and tumor epithelium. The correlation between iNOS and SMA in pleomorphic adenoma was significant [P < 0.001]. The results of the present study suggested that iNOS plays an important role in pathogenesis of pleomorphic adenoma and the presence of iNOS in normal salivary ducts and pleomorphic adenoma is most likely due to expression by myoepithelial cells