Breast cancer is a leading cause of
cancer death among women, and the failure of normal apoptosis has been proved in the development of
breast cancer. The
phytoestrogen,
calycosin, is extracted from Chinese medical herb
Radix astragali. We recently reported that
calycosin successfully stimulated proliferation of ER-positive MCF-7 human
breast cancer cells at low concentration. In the present study, we assessed the proapoptotic function of
calycosin in MCF-7 cells at high concentration in vitro, as well as the possible mechanism of its effect. MCF-7 cells were treated with different concentrations of
calycosin, and then detected by MTT assay for cellular viability, Hoechst assay, and flow cytometry for apoptosis. RASD1 is identified as a Ras-family member and a regulator in MAPK-mediated cascade leading to cell proliferation or apoptosis. To provide insight into the functions of RASD1 signaling pathway in
calycosin-induced apoptosis, the expression of Bcl-2, Bax, and RASD1 in
calycosin-treated cells were determined by Western blot assay. The results showed that high concentrations of
calycosin significantly suppressed the proliferation of MCF-7 cells and promoted cell apoptosis. Moreover, compared with control group, the expression of Bcl-2 decreased with
calycosin in MCF-7 cells, while Bax increased, which was significantly correlated with elevated expression of RASD1. Together, we present evidence that at relatively high concentration
calycosin triggered cell apoptosis through the mitochondrial apoptotic pathway by upregulating RASD1. And for the first time, this study revealed that
calycosin may have potential as a therapeutic agent for the treatment of
breast cancer.