AUTOMATED AND QUANTITATIVE IMMUNOCYTOCHEMICAL ASSAYS OF BCL-2 PROTEININ BREAST CARCINOMAS

Expression of the bcl-2 gene was investigated in 218 human breast carc inomas by immunohistochemical analysis. Immunodetections were assessed using (1) frozen sections, (2) documented commercially available mono clonal antibody (bcl-2/124, Dako), (3) automation of immunoperoxidase technique (Ventana) and (4) quantitative evaluation of results by imag e analysis (SAMBA) and statistical analysis of quantitative data (BMDP software). Bcl-2 protein expression was correlated with current progn ostic indicators and with molecular markers detected by the same proce dure as for Bcl-2. It was shown that Bcl-2 expression is not related t o patients' age, tumour size and type or lymph node status, but an inv erse relationship was observed between Bcl-2 and tumour grade (P < 0.0 001). An inverse relationship was also observed between Bcl-2 expressi on and p53 (P < 0.0001), Ki67/MIB1 antigen- (P = 0.0012), and P-gp- (P = 0.002) positive immunoreactions. In contrast, anti-Bcl-2 positive r eaction was significantly associated with ER-positive (P < 0.001) and with ER/PR-positive or ER/PR/pS2-positive immunoreactions (P less than or equal to 0.005). Bcl-2 expression was independent of CD31 and cath epsin D expression. Thus, Bcl-2 protein, thought to be antiapoptotic, exhibits parodoxical expression in human breast carcinomas. It is stro ngly detected in low-grade tumours (well-differentiated) with low (MIB 1) growth fraction, but is independent of the tumour progression (size , node status, CD31, and cathepsin D). Bcl-2 acting on apoptosis is re lated to p53 gene abnormalities in breast carcinomas. Bcl-2 protein ex pression may also be involved in response to endocrine therapy (associ ated to ER/PR/pS2 positive immunoreactions) and probably with chemores istance mechanisms (inverse relationship with P-gp).