ABSTRACT
Recent studies have suggested that nitric oxide (NO) exerts various effects on aspects of tumor biology, including angiogenesis and metastasis. There have been, however, scanty reports on nitric oxide synthase (NOS) response for tumors of the head and neck. This study was carried out to assess the distribution of both endothelial NOS (eNOS) and inducible NOS (iNOS) in normal salivary gland tissue and in pleomorphic adenoma by using immunohistochemistry. In the present study, eNOS and iNOS were higher expressed in pleomorphic adenoma than adjacent normal salivary gland tissue, suggesting that up-regulation of this enzyme is associated with tumor progression. Additionally, eNOS and iNOS expression were higher in epithelial components than in mesenchymal components. Overall, iNOS expression was higher than eNOS expression in pleomorphic adenoma. In normal tissues adjacent to pleomorphic adenoma, iNOS expression was higher in the mesenchymal type than in the epithelial type of pleomorphic adenoma. It is suggested that NO may play a role in the tumorgenesis and propagation of pleomorphic adenoma.