THE EXTENT OF APOPTOSIS IS INVERSELY ASSOCIATED WITH BCL-2 EXPRESSIONIN PREMALIGNANT AND MALIGNANT BREAST-LESIONS

Aims: In this study we investigated the extent of apoptosis in benign, premalignant and malignant breast lesions and its association with th e immunohistochemical expression of bcl-2 oncoprotein. Methods and res ults: In order to detect apoptotic cells and bodies in tissue sections , the 3'-end DNA labelling method was used. Immunohistochemical staini ng was performed by using the avidin-biotin-peroxidase complex techniq ue, A monoclonal antibody agains bcl-2 oncoprotein was used and the sp ecificity of the antibody was confirmed by immunoblot analysis. Accord ing to the results the extent of apoptosis, as determined by the apopt otic index, was lowest in benign ductal hyperplasias and sclerosing ad enoses (0.15% and 0.07%, respectively), It was moderately elevated in atypical hyperplasias and in-situ carcinomas (0.20% and 0.40%, respect ively) and highest in invasive carcinomas (0.76%). In ductal invasive carcinomas, grade I lesions showed a lower apoptotic index (0.52%) tha n grade II (0.72%) and grade III (1.17%) carcinomas, The apoptotic ind ex was not significantly lower in lobular (0.82%) than in ductal invas ive carcinomas (0.85%), bcl-2 immunohistochemistry was inversely relat ed to the apoptotic index, In all cases studied the inverse associatio n was very strong (P=0.0004) but it was also present when only carcino mas were analysed (P=0.01). In benign and atypical hyperplasias, bcl-2 positivity was observed in all cases, but such cases were less freque nt in in-situ lesions and in invasive carcinomas. Conclusions: The res ults show that there is an inverse relationship between the extent of apoptosis and bcl-2 expression in breast lesions suggesting that its e xpression affects the regulation of apoptosis in them.