Regulation of cell adhesion by heparan sulfate proteoglycan in adenomatoid odontogenic tumour

During recent years, attention was drawn to the role of cell adhesion in tumour development and progression. Cell-cell and cell-extracellular matrix interaction is crucial with regard to tumorous transformation and tumour spreading. There are numerous data indicating that the expression of syndecan-1 an important transmembrane proteoglycan undergoes changes during the development of several tumours. CD 138 antibody reacts with the core protein of syndecan-1, cell surface integral membrane heparin sulfate and chondroitin sulfate containing proteoglycan that binds to interstitial extracellular matrix molecules, thereby regulating cell adhesion. The predominant location of syndecan-1 is on epithelial cells where its expression correlates with normal epithelial organization. Previous studies have demonstrated that decreased expression of CD 138 is linked to malignant progression. Hitherto, few studies on the expression of CD138 in odontogenic tumours have been published and no studies have been found regarding the expression of this marker in adenomatoid odontogenic tumour [AOT]. Therefore, this study was carried out to highlight the recent concepts of cell adhesion in tumour development and progression in AOT using CD 138 monoclonal antibody. In respect to this, formalin-fixed, paraffinembedded tissue sections of 7 cases of AOT were selected in an attempt to clarify the peculiar histopathological features of this lesion. All studied cases showed positive reaction to the marker used, however differences were observed among the studied cases regarding areas of immunoreactivity and optical density of the positive areas. Overexpressions of CD138 were observed as cytoplasmic immunoreactivity especially in the spindle cells bordering the sheets and masses of the polyhedral cells and in the scanty stromal cells. The duct like structures and masses of polyhedral cells showed negative reactions. The results of the present study explain why AOT is a benign non-aggressive lesion

Correlations of cell proliferation and transformation with histopathological features of adenomatoid odontogenic tumour

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