Apoptosis-related factors (TRAIL, DR4, DR5, DcRl, DcR2, apoptotic cells) and proliferative activity in ameloblastomas

Background: Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a recently identified death factor that acts as a potent apoptosis inducer in ameloblastomas. Materials and Methods: The expression of TRAIL and its receptors (TRAIL-R), and the location of apoptotic cells were evaluated in 15 cases of ameloblastoma using immunohistochemistry and an in situ DNA nick-end labeling method. The proliferative activity of ameloblastomas was analyzed by determining the Ki-67 labeling index. Results: TRAIL and TRAIL-R were diffusely expressed in ameloblastomas, without clear correlation with the location of apoptotic cells. Apoptosis and proliferation were opposite in the peripheral and central components of the ameloblastomas. In some ameloblastoma variants, apoptosis and proliferation seemed to modify in the same direction. Conclusion: TRAIL and its receptors might be involved in neoplastic transformation of odontogenic epithelium and might suggest some intrinsic regulation of neoplastic cell proliferation and death in ameloblastomas, thus explaining their slow growth and inability to metastasize.