Immunohistochemical expression of Bcl-2 protein in breast lesions: correlation with Bax, p53, Rb, C-erbB-2, EGFR and proliferation indices.

Expression of bcl-2 protein was investigated and correlated with Bax, p53 and Rb proteins, c-erbB-2, EGFR and the proliferation indices PCNA, Ki-67 and MIB1 as well as with the conventional clinicopathological parameters in 95 cases for breast cancer tissue and 20 cases of benign hyperplastic lesions. Bcl-2 and Bax proteins immunoreactivity was detected in normal, hyperplastic and neoplastic breast epithelium. Expression of the bcl-2 protein was detected in 40% of carcinomas (> 10% positive neoplastic cells) and 85.2% of the benign hyperplastic lesions. Bax protein expression was detected in 8.1% of the carcinomas and 5.3% in the hyperplastic group. Rb and p53 proteins were detected in 75.5% and 45.5% of carcinomas. No relationship was observed between bcl-2 expression and patient's age, tumour size, tumour type and grade, lymph node status, Rb protein expression and proliferation indices. However, a strong positive relationship was detected between bcl-2 and Bax (p = 0.008), estrogen (ER) (p = 0.007) and progesterone receptors' (PgR) status (p = 0.0003). An inverse correlation with p53 protein (p = 0.004) was detected. Furthermore, a strong correlation was also observed between pRb and p53 (p = 0.001). The results indicate that in breast cancer bcl-2 protein expression may be under hormonal control. Since the expression is bcl-2 protein was inversely correlated with p53 protein expression, we suggest that bcl-2 may be related with favourable outcome in breast cancer.