Expression of estrogen receptor beta in the breast carcinoma of BRCA1 mutation carriers

The study group consisted of 48 women with BRCA1 gene mutations confirmed by multiplex PCR assay. The patients were tested for three most common mutations of BRCA1 affecting the Polish population (5382insC, C61G, 4153delA). Immunostaining for ERα, ERβ and PgR (progesterone receptor) was performed using monoclonal antibodies against ERα, PgR (DakoCytomation), and polyclonal antibody against ERβ (Chemicon). The EnVision detection system was applied. The study population comprised a control group of 120 BC operated successively during the years 1998–99.The results of our investigation showed that BRCA1 mutation carriers were more likely to have ERα-negative breast cancer than those in the control group. Only 14.5% of BRCA1-related cancers were ERα-positive compared with 57.5% in the control group (P < 0.0001). On the contrary, the expression of ERβ protein was observed in 42% of BRCA1-related tumors and in 55% of the control group. An interesting finding was that most hereditary cancers (75% of the whole group) were triple-negative: ERα(-)/PgR(-)/HER-2(-) but almost half of this group (44.4%) showed the expression of ERβ.In the case of BRCA1-associated tumors the expression of ERβ was significantly higher than the expression of ERα. This may explain the effectiveness of tamoxifen in preventing contralateral breast cancer development in BRCA1 mutation carriers.In 1990 Hall et al. discovered that familial breast cancer is associated with a defect in one of the genes located in the 17q21 chromosome [1]. This finding began a new era of research into hereditary breast cancer and consequently led to the identification of the BRCA1 and BRCA2 suppressor genes in 1994 and 1995, respectively. Although the structures and localization of the BRCA1 and BRCA2 genes differ, their functions seem to be similar because their transcripts are involved in the same processes [2-6]. These genes are responsible for maintaining the proper course of the cell cycle, for the repair of DNA damage,