IMMUNOHISTOCHEMICAL DETERMINATION OF TUMOR-ASSOCIATED ANTIGENS IN AMELOBLASTOMA AND ODONTOGENIC CYSTS

Abstract

Transforming growth factor atpha (TGF-a), parathyroid hormone-tike proteins (PTHLP) and oncogene p53 proteins have all been demonstrated in a variety of human tumors anil have been implicated as causes of tumor cell aggressiveness. The present study determined the existence of these peptides and their immunohistochemicat profiles in ameloblastomas. Odontogenic keratocysts and dentigerous cysts were included for comparison. Formalin fixed paraffin embedded sections of 22 amelohlastom as, 18 odontogenic keratocysts and 17 dentigerous cysts were examined immunohistochemicalfy. Results showed that 14/22 ameloblastomas demonstrated a very strong positive staining for TGF-a in approximately 95% of the amelohlasts. Staining intensity in the remainder of the ameloblastomas was moderate in 2/22, weak in 1/22 samples and was focal in distribution in 5/22 sections. Immunoreacttvity for PTHLP was demonstrated in 20/22 ameloblastomas with variable levels of staining intensity ranging from very strong in 9/22, to moderate in 5/22 and weak in 3/22 specimens. The most intense staining for both antigens was demonstrated at the peripheral margins of invading tumor cells. The staining intensity in the majority of odontogenic cysts was weak or absent. Occasional focal staining with approximately 5% cell positivity and variable staining intensity was found in some specimens. Positive immunoreactivity for p53 oncogene was not demonstrated in any odontogenic lesion types examined in this study. In conclusion, the apparent in situ immunolocalization of TGF-a and PTHLP in ameloblast tumor cells indicates that these peptides were produced locally in ameloblastomas. Secondly, their expression were independent of ameloblastoma sub-types and were not altered by fixation methods used to process the formalin fixed paraffin embedded sections. Finally, the original assumptions tluit ameloblastomas are benign but locally aggressive tumors was supported in this study by showing that these tumors lack p53 oncogene proteins which are indicative of potential malignancies.