BACKGROUND: To clarify the role of p53 homologs in oncogenesis and 
cytodifferentiation of odontogenic tumors, expression of p63 and p73 was 
analyzed in ameloblastomas as well as tooth germs.
METHODS: Tissue specimens of nine tooth germs and 48 benign and five malignant 
ameloblastomas were examined by immunohistochemistry and reverse 
transcriptase-polymerase chain reaction (RT-PCR) for the expression of p63 and 
p73.
RESULTS: Immunoreactivity for p63 and p73 was evident in epithelial cells 
neighboring the basement membrane in developing and neoplastic odontogenic 
tissues. p63 expression in desmoplastic ameloblastomas was significantly higher 
than in acanthomatous and granular cell ameloblastomas, and ameloblastic 
carcinomas showed higher p63 expression than metastasizing ameloblastomas. p73 
expression was significantly higher in plexiform ameloblastomas than in 
follicular ameloblastomas, and basal cell ameloblastomas showed higher p73 
expression than granular cell ameloblastomas. mRNA transcripts for Delta Np63 
and TAp73 were detected in all developing and neoplastic odontogenic tissues. 
TAp63 mRNA was expressed in five of eight tooth germs, 16 of 34 ameloblastomas, 
and one of one malignant ameloblastoma, whereas Delta Np73 mRNA was recognized 
in one of eight tooth germs, nine of 34 ameloblastomas, and one of one malignant 
ameloblastoma.
CONCLUSION: The expression of p63 and p73 suggests that these p53 homologs play 
a role in differentiation and proliferation of odontogenic epithelial cells. 
Variations of predominantly expressed isoforms suggest that p63 and p73 might 
differentially function in odontogenic tissues.