APOPTOSIS IS INVERSELY RELATED TO BCL-2 BUT NOT TO BAX EXPRESSION IN SALIVARY-GLAND TUMORS

Aims: We investigated the extent of apoptosis in 55 benign and maligna nt salivary gland tumours and its association with the immunohistochem ical expression of bcl-2 and bar. Methods and results: Apoptosis was d etected in histological sections by the 3'-end DNA labelling method, b cl-2 and bar protein expression was determined by immunohistochemistry . The frequency of apoptosis was clearly higher in malignant than in b enign tumours. In pleomorphic adenomas and Warthin's tumours the avera ge apoptotic index was 0.01% (range 0.00-0.07%) while in the malignant salivary gland tumours it was 0.42% (range 0.00-1.75%), Immunohistoch emical bcl-2 expression was observed in all pleomorphic adenomas and W arthin's tumours and in most cases the expression was strong, In malig nant tumours, 9/25 cases showed no expression and in the rest of the c ases, apart from adenoid cystic carcinomas, the bcl-2 expression was o ften weak, There were significantly more cases with no or weak bcl-2 p ositivity in malignant than in benign salivary gland tumours (P=0.001) , There was a statistically significant association between a weak bcl -2 expression and a high frequency of apoptosis (P=0.02), In contrast to bcl-2, strong bar expression was found in both benign and malignant tumours and was not associated with the frequency of apoptosis, Concl usions: The low bcl-2 expression in malignant tumours suggests that do wn-regulation of its expression might contribute to their higher frequ ency of apoptosis.