RESUMO
Recently, 2 highly related and widely expressed molecules, CREB- binding protein [CBP] and p300, have emerged as important cofactors for a broad number of transcription factors. The p300 gene is a potential tumour suppressor and its expression increases during progression from late Gl into M phase of the cell cycle. p300 transcriptional coactivators are also targeted by oncogenic viruses. p300 is involved in cell growth, transformation and development and has an important role in regulation of cell proliferation. However, many questions regarding its role in transcriptional regulation remain unanswered and no study until now was found describing the immunoreactivity of this novel marker in adenomatoid odontogenic tumour [AOT]. Therefore, this study was carried out to highlight the recent concepts of cell transformation and proliferation in AOT using p300 monoclonal antibody. In respect to this, 7 cases of AOT were selected in an attempt to clarify the peculiar his-topathological features of this lesion. All studied cases showed positive reaction to the marker used, however differences were observed regarding areas of immunoreactivity and optical density of the positive areas among studied cases. Overexpression of p300 was observed as nuclear immunoreactivity especially in the rounded or polyhedral cells forming the masses and sheets of odontogenic epithelial cells, also in the columnar cells lining the duct like structures. Conversely, the flat or spindle cells showed negative immunoreactivity. Invasion of the connective tissue capsule by slender of tumor cells was observed in some cases. The results of the present study suggest that the neoplastic cells in AOT may be represented by the population of rounded or polyhedral cells and the cells forming the duct like structures. Therefore, AOT should be regarded as a true neoplasm and not hamartomatous in nature as sometimes previously thought