Detection of cell cycle-related factors in ameloblastomas

To determine whether cell cycle regulation or alteration plays a role in on cogenesis and cytodifferentiation of odontogenic epithelium, cell cycle-rel ated factors, including cyclin D1, p16(INK4a), p21(WAF1/Cip1) and p27(Kip1) proteins, DNA topoisomerase II alpha and histone H3 mRNA, were examined in 8 tooth germs and 31 ameloblastomas. Cyclin D1 was expressed in epithelial cells near the basement membrane in tooth germs and ameloblastomas, sugges ting that this protein participates in cell proliferation in odontogenic ep ithelium. Immunoreactivity for p16 protein was observed in most epithelial cells in tooth germs and ameloblastomas. Expression of p21 protein was dete cted in most epithelial cells in tooth germs and ameloblastomas, but not in keratinizing or granular cells in variants of ameloblastomas. Expression o f p27 protein was chiefly found in central polyhedral cells and keratinizin g cells in tooth germs and ameloblastomas. These cyclin-dependent kinase in hibitors were well preserved in ameloblastomas as compared with tooth germs , suggesting that the odontogenic epithelium is strictly regulated by these factors. The cell cycle phase/cellular proliferation markers, DNA topoisom erase II alpha and histone H3 mRNA, were localized in scattered epithelial cells attached to the basement membrane in tooth germs and ameloblastomas.