UNIVERSITY OF ILLINOIS
The selective estrogen receptor modulator tamoxifen is efficacious in the treatment and prevention of breast cancer, the most common cancer in women. However, tamoxifen treatment causes menopausal symptoms including hot flashes. In addition, tamoxifen causes enhanced endometrial cell proliferation resulting in an increased endometrial cancer risk. The latter effect is thought to be due to pro-estrogenic effects specific to the endometrium. In this patient population, the use of botanical dietary supplements for the alleviation of menopausal symptoms caused by tamoxifen is very common. Red clover and black cohosh products are the most frequently used botanicals for these indications. However, very few studies about the interaction of these botanicals with tamoxifen have been reported and the safety and effect on the efficacy and side effects of tamoxifen have not been established yet. Black cohosh and red clover contain antioxidative, antiproliferative, antiinflammatory, and detoxification enzyme inducing compounds, which could inhibit the carcinogenic initiation step or retard the promotion and progression of precancerous cells. The central hypothesis of this project is that black cohosh and red clover reduce the carcinogenic effects of tamoxifen on the endometrium by inhibition of cell proliferation (Aim I) and through enhancing detoxification pathways (Aim 2). To support this hypothesis we propose two specific aims. In the first aim, we analyze the effect of red clover and black cohosh on tamoxifen-stimulated endometrial cancer and the influence of these extracts on tamoxifen's efficacy in breast cancer cells. Recent data strongly suggest that black cohosh and red clover can attenuate tamoxifen-stimulated endometrial cancer growth by inhibiting cell proliferation. We will first measure the influence of these botanicals on tamoxifen stimulated endometrial cell proliferatin in endometrial cell lines and on tamoxifen's anti-estrogenic and anti-proliferative activity in breast cancer cells. To identify active compounds, we will analyze the anti-proliferative and anti-estrogenic effect of the isolated compounds in endometrial cancer cells. Promising compounds and the extracts might also be tested in juvenile rats for their effect on tamoxifen’s uterotrophic activity. When promising activities have been seen in these experiments with the extracts, we will then analyze the endometrial tumor growth in ovarectomized athymic nude mice, an established endometrial cancer model for studying hormonal influences. To elucidate the mechanism of interaction, we will examine the expression of estrogen sensitive genes and their corresponding proteins, which are thought to be important for tamoxifen mediated tumor promotion, in vivo and in vitro. In the second aim, we plan to analyze the effect of black cohosh or red clover on the metabolic activation and detoxification pathways of tamoxifen. Our data indicate that black cohosh and red clover have the potential to upregulate the cellular antioxidative response machinery, thus reducing the carcinogenic effect of tamoxifen’s reactive metabolites. Importantly, we also examine the influence of black cohosh and red clover on 4-hydroxytamoxifen's efficacy against estrogen carcinogenesis in breast cancer cells. Finally, analysis of the effect of the extracts or compounds on the metabolic activation of tamoxifen in collaboration with Dr. Nikolic, will ascertain whether black cohosh or red clover influence tamoxifen’s efficacy.