Immunohistochemical detection and distribution of enamelysin (MMP-20) in human odontogenic tumors

Enamelysin is a tooth-specific protease that was initially isolated from po rcine enamel organ and subsequently from human odontoblasts. Since this pro tease is thought to play important roles in tooth development, the evaluati on of enamelysin in odontogenic tumors may aid our understanding of the his togenesis and cell differentiation of such lesions. A monoclonal antibody ( 203-1C7) was generated against synthesized human enamelysin oligopeptide an d was used to assess the immunolocalization of enamelysin in healthy develo ping tooth germs and various types of odontogenic lesions. In tooth germs, enamelysin expression was detected only in the secretory enamel. Thus, 203- 1C7 may serve as an enamel-specific marker in the late stage of enamel matr ix development and calcification. In odontogenic lesions, strong enamelysin staining was demonstrated in the immature enamel matrix of ameloblastic fi bro-odontomas and odontomas. Furthermore, enamelysin was also detected in g lobular amyloid masses and calcified foci in calcifying epithelial odontoge nic tumors, hyaline droplets, small and large mineralized areas in adenomat oid odontogenic tumors, and a portion of ghost cells in calcifying odontoge nic cysts. Positive reactivity was also observed in selected tumor cells in some of these tumors. No intracellular staining for enamelysin was detecte d in ameloblastomas or the ameloblastic portion of ameloblastic fibro-odont omas. Also, enamelysin was not detected in dentin, dysplastic dentinoid hya line matrices, and cementum that were present within the tumors examined. T hus, taken together, our results suggest that the enamelysin-specific monoc lonal antibody (203-1C7) may be utilized as a marker of early enamel develo pment and that enamelysin may be involved in the pathogenesis of specific o dontogenic tumors.