BAX In situ hybridization and proliferating cell nuclear antigen immunohistochemical expressions in salivary gland tumours


Background: Epithelial salivary gland tumours are relatively uncommon and constitute a wide spectrum of variablemorphologic and biologic entities. The cell proliferation / death balance is most important in the development ofsalivary gland tumours. The aim of this study was to examine the expression of PCNA protein immunohistochemicallyand Bax mRNA gene using in situ hybridization techniques and to correlate between the clinicopathological featuresof salivary gland tumours with the expressions of PCNA protein and Bax mRNA.Materials and Methods: Forty nine formalin fixed paraffin embedded tissue blocks of epithelial salivary gland tumourswere used in this study. Haematoxylin and Eosin stain was used for reassessment of the histopathologic diagnosis. Thecell proliferation activity was examined by proliferating cell nuclear antigen (PCNA) immunohistochemistry andproapoptotic cell death Bax mRNA gene was analysed by in situ hybridization techniques.Results: Immunohistochemical analysis show high expression of PCNA and was noted in 8 of 12 pleomorphicadenoma cases (66.67%), 15 of 19 adenoid cystic carcinoma cases (78.95 %), 6 of 7 mucoepidermoid carcinomacases (85.71%), and 3 of 5 adenocarcinoma case (60 %). Significant difference was found between labeling index ofbenign and malignant salivary gland tumours, while no significant relationship was noted in labeling index betweenadenoid cystic carcinoma and mucoepidermoid carcinoma neither between mucoepidermoid carcinoma andadenocarcinoma. In situ hybridization detection show low expression of Bax and was noted in only 3 cases ofpleomorphic adenoma cases (25%), 10 cases in adenoid cystic carcinoma cases (52.63 %), however,mucoepidermoid carcinoma showed high expression of these markers than other salivary gland tumours, whereasadenocarcinoma show equal number of cases expressed both PCNA protein and Bax mRNA. No significantrelationship was demonstrated between the immunostaining PCNA or Bax and the morphological growth pattern orpatient clinical profile. Positive significant correlation was found between PCNA and Bax mRNA in pleomorphicadenoma, adenoid cystic carcinoma, mucoepidermoid carcinoma and adenocarcinoma cases.Conclusion: The high proliferative rate could explain the natural course of these tumours and the decreasedexpression of bax in salivary gland tumours indicate that loss of bax expression might give the tumour cells a doublegrowth advantage because uncontrolled proliferation is combined with reduce cell death rate. The interaction maytrigger a multistep process which is able to promote and may play a role in salivary gland tumour genesis, possibly byinhibiting the apoptosis mediated by Bax