Ameloblastoma Tissue Molecular Pathology

Ameloblastomas are the most commom tumors among odontogenic tumors. It is difficult to be controlled in clinic due to its biological chacteristics such as growing invasively and recurring easily. During past decades, although many researches includingmorphology.immunohistochemistry, and even molecular biology, have been performed, little is known about the mechanism of the development of ameloblastomas. Bone morphogenetic protein(BMP) is bone— induced growth factors, exists normally in the matrix of bone and dentin. Immunohistochemical study showed that enamel epithelium including ameloblasts is positive to monoclonal antibody against BMP. Ameloblastomas are odontogenic tumors, and the expression and distribution of BMP in ameloblastomas are not clear. In this study, the expression of BMP genes, as well as transforming growth factor-β (TGF—β), epidermoid growth factor ( EGF) and its receptor (EGFR) , oncogenes( neu, erbB- 2, bcl- 2), tumor suppressing gene(P⁵³), and amelogenin, was observed in 40 cases of ameloblastomas using immunohistochemistry, in situ hybridization, Northern blot, Southern blot, PCR, and PCR- SSCP. The results showed that, by immunohistochemistry, although enamel epithelium of normal tooth germs was strongly positive to BMP antibody ,no positive reaction was found in all cases of ameloblastomas. Overexpression of BMP genes was observed in ameloblastomas by in situ hybridization.In order to determine if the mutation of BMP genes occurred during the development of ameloblastomas, PCR-SSCP was performed in 4 cases of ameloblastomas, no evidence of mutation was observed. When tumor tissues of ameloblastomas were implanted into mouse muscle, no bone or cartilage formation was found even 4 weeks after implantation. Those re-...