Apoptosis and proliferation are processes associated with the development and
progression of breast cancer. The sensitivity of tumour cells to the induction of
apoptosis depends on the balance between pro- and anti-apoptotic proteins.
The expression of Bak and Bcl-2 was examined using an immunohistochemical
method in 71 primary breast cancers. Furthermore, Bcl-2 and Bak were assessed
in the normal mammary gland as well as in benign mammary dysplasia adjacent
to breast cancer. Positive immunostaining for Bcl-2 was observed in 77.8% of
cases of normal breast epithelium (NBE), 93% of benign dysplasia without intraductal
proliferation (BBD) as well as in 94% of intraductal proliferative lesions of
the breast (BIPL). Expression of Bak was detected in 39% of cases of NBE, 45%
of BBD and in 67% of BIPL. In breast cancer Bcl-2 and Bak expression was found
in 83% and 70% of the cases studied, respectively. Increased Bcl-2 expression in
primary tumours significantly correlated with favourable prognostic factors, namely
pT1, G2 and lack of metastases to the regional lymph nodes (p < 0.01,
p < 0.03, p < 0.02, respectively). There were no relationships between Bak and
the clinicopathological features studied, but our results indicate changes in the
expression of Bak during breast cancer development and progression. It would
appear to be important to assess and compare pro- and anti-apoptotic proteins
between normal mammary gland, benign mammary dysplasia and the primary
tumours of breast cancer. This knowledge should be helpful in understanding
breast cancer development and progression