Immunohistochemical Analysis of Benign Mixed and Mesenchymal Odontogenic Tumors

Abstract

Benign mixed and mesenchymal odontogenic tumors (ameloblastic fibroma, ameloblastic fibrodentinoma, ameloblastic fibro-odontomas, odontogenic fibroma and odontogenic myxoma) were immunohistochemically examined using antibodies against amelogenin, cytokeratin 19, bcl-2, hepatocyte growth factor (HGF), c-Met, transforming growth factor-β (TGF-β), TGF-β receptors and Ki-67 to know cytodifferentiation, epithelial-mesenchymal interaction and proliferative activity. Expression of amelogenin was detected in odontogenic epithelial cells and enamel matrices in ameloblastic fibro-odontomas, and cytokeratin 19 was expressed in odontogenic epithelial cells, indicating odontogenic epithelial properties. Expressions of bcl- 2, HGF, TGF-β, TβR I and TβR II were detected in odontogenic epithelial and mesenchymal cells in mixed and mesenchymal odontogenic tumors, while expression of c-Met was detected in odontogenic epithelial cells. Odontogenic epithelial and mesenchymal cells sporadically showed positive reactions for Ki-67 in mixed and mesenchymal odontogenic tumors, and no apparent differences were obtained among these tumors or between the components. Conclusion: Immunohistochemical localization of HGF, TGF-β and their receptors suggests that these growth factor signaling are effective in the epithelial component in paracrine and autocrine manner in mixed and mesenchymal odontogenic tumors. These results of growth factor signaling suggest that certain epithelial-mesenchymal interactions are related to neoplastic cell growth in these tumors.