Kousuke Ohki

Detection of CD133, Bmi‐1, and ABCG2 in ameloblastic tumors

BACKGROUND To investigate the roles of stem cell-related molecules in oncogenesis and cytodifferentiation of odontogenic tumors, expression of CD133, Bmi-1, and ATP-binding cassette subfamily G member 2 (ABCG2) was analyzed in ameloblastic tumors as well as in tooth germs. METHODS Tissue specimens of 12 tooth germs, 47 ameloblastomas, and six malignant ameloblastic tumors were examined using reverse transcriptase-polymerase chain reaction (RT-PCR) and immunohistochemistry to determine the expression of CD133, Bmi-1, and ABCG2. RESULTS mRNA expression of CD133, Bmi-1, and ABCG2 was detected in all samples of normal and neoplastic odontogenic tissues. Immunohistochemical reactivity for CD133 and Bmi-1 was evident in odontogenic epithelial cells neighboring the basement membrane in tooth germs, ameloblastomas, and metastasizing ameloblastomas, and ameloblastic carcinomas and clear cell odontogenic carcinomas showed reactivity for CD133 and Bmi-1 in most neoplastic cells. The level of CD133 immunoreactivity in malignant ameloblastic tumors was significantly higher than the levels in tooth germs and ameloblastomas. Immunoreactivity for ABCG2 in odontogenic epithelial components was detected in some ameloblastic tumors but not in tooth germ tissues. Some granular neoplastic cells in granular cell ameloblastomas showed ABCG2 expression. The level of ABCG2 immunoreactivity in malignant ameloblastic tumors was significantly higher than that in tooth germs. CONCLUSION Expression of CD133, Bmi-1, and ABCG2 in tooth germs and ameloblastic tumors suggests that stem cell-related molecules might control the maintenance of odontogenic tissues. Expression of these molecules is possibly involved in oncogenesis, cell differentiation, and malignant potential of odontogenic epithelium.

Detection of Notch signaling molecules in ameloblastomas

BACKGROUND To evaluate the roles of Notch signaling in the oncogenesis and cytodifferentiation of odontogenic tumors, expression of Notch receptors and ligands was analyzed in ameloblastomas as well as in tooth germs. METHODS Tissue specimens of nine tooth germs and 32 ameloblastomas were examined by reverse transcriptase polymerase chain reaction and by in situ hybridization to determine the expression of Notch1, Notch2, Notch3, Delta1, and Jagged1. RESULTS mRNA expression of Notch1, Notch2, Notch3, Delta1, and Jagged1 was detected in all samples of normal and neoplastic odontogenic tissues. In tooth germs, Notch receptors were expressed in odontogenic epithelium (except for inner enamel epithelium), and expression of Notch ligands was lower in inner enamel epithelium than in other epithelial components. Odontogenic mesenchymal components were weakly reactive with these Notch signaling molecules. Ameloblastomas showed expression of Notch receptors and ligands in central polyhedral neoplastic cells. Notch2, Delta1, and Jagged1 were expressed in some neoplastic cells neighboring the basement membrane. Expression of Notch receptors and ligands was not found in keratinizing cells or granular cells in ameloblastoma variants. Stromal cells were weakly reactive with these Notch signaling molecules. CONCLUSION Expression of Notch receptors and ligands in tooth germs and ameloblastomas suggests that Notch signaling might control cell differentiation and proliferation of normal and neoplastic odontogenic epithelium.