The effects of black cohosh on the regulation of Estrogen receptor alpha in breast cancer cells

The North American plant Cimicifuga racemosa, also known as black cohosh, is an herb that has been used for centuries by numerous cultures for its wide range of health benefits. Recently, black cohosh has gained attention for its hormonal effects which have the potential to alleviate female medical conditions including menopause. Black cohosh has been used in menopausal women to relieve hot flashes, profuse sweating, and sleep disturbances. As the usage of hormone replacement therapy is declining due to its adverse affects in women with cancer, many are turning to herbal remedies like black cohosh (BC) to treat menopausal symptoms. Studies indicate that this flavonoid may act as a SERM, thus inducing inhibitory growth effects on hormone dependent cancer cells. Therefore, it is crucial to determine whether the effects of black cohosh involve ER-alpha. Previous studies from our lab have shown the estrogen receptor (ER-alpha) to be a possible molecular target for BC. In this study, the effects of black cohosh alone and in combination with hormones and anti-hormones were examined with cellular viability and expression and cytolocalization of ER-alpha in ER (+) T-47D breast cancer cells. In order to deplete any endogenous steroids or effectors, breast cancer cells were cultured in medium containing 5% charcoal-stripped fetal bovine serum for six days. Western blot analysis revealed alterations in the expression of ER-alpha after 24 hours of treatment with varying concentrations of BC (5 - 100 μM). BC induced a concentration-dependent decrease in ER-alpha protein levels, with a 57% reduction occurring with 100 μM BC when compared to DMSO. In order to determine the influence of BC on the growth of breast cancer cells, image cytometric analysis with propidium iodide staining was utilized to quantify alterations in T-47D cell number and viability. After six days of treatment, a 23 - 61% decrease in T-47D cell viability was observed upon treatment with 5 - 100 μM BC. The ideal concentration of black cohosh (100 μM) was used in combination with hormones and anti-hormones in an effort to further understand the possible similarities between this compound and other known effectors of ER-alpha. After a 24-hour concomitant treatment of 100 μM BC and 10 nM E2 on T-47D cells, down-regulation of ER-alpha protein levels was observed. When BC was used in combination with the pure ER-alpha antagonist ICI (1 μM), similar effects were detected. The proliferative effect of estrogen (E2) was reduced when treated in the presence of BC. Delineating the role of BC in the regulation of ER-alpha and its mechanisms of action may be important in understanding the influence of BC and hormone receptors in breast cancer.