Effects of genistein and daidzein, in combination, on immunoexpression pattern of ER, PR and HER-2/neu during 7, 12-dimethylbenz (a) anthracene induced mammary carcinogenesis in rats

The status of estrogen receptor (ER), progesterone receptor (PR) and human epidermal growth factor receptor-2 (HER-2/neu) has been used as routine markers for diagnosis, prognosis and response to treatment of breast cancer. Aim of the present study was to investigate the effects of genistein and daidzein, in combination, on immunoexpression pattern of ER, PR and HER2/neu receptors during 7,12-dimethylbenz(a)anthracene (DMBA) induced mammary carcinogenesis in Sprague-Dawley rats. A single subcutaneous injection of DMBA (25 mg/rat) in the mammary gland developed mammary carcinoma in rats. Mammary tissues of control and experimental rats were routinely processed and paraffin embedded, 2-3μm sections were cut in a rotary microtome and mounted on clean glass slides. Immunohistochemical staining of mammary tissue was performed and each slide was microscopically analyzed and enumerated for the percentage of the positively stained cells semi-quantitatively and grading was then made. Immunohistochemical analysis showed over expression of ER, PR and HER2/neu in the mammary tissues of DMBA treated rats. Oral administration of genistein+daidzein (20mg+20mg/kg body weight) in combination, to DMBA treated rats significantly prevented the over expression of ER, PR and HER2/neu in the mammary tissues. Genistein and daidzein inhibited mammary epithelial cell proliferation probably by preventing the over expression of ER, PR and HER2/neu in the mammary tissues of Sprague-Dawley rats, during DMBA induced mammary carcinogenesis.