Calycosin Stimulates Proliferation of Estrogen Receptor-Positive Human Breast Cancer Cells Through Downregulation of Bax Gene Expression and Upregulation of Bcl-2 Gene Expression at Low Concentrations

Background: Calycosin is one of main components in the herb Radix astragali and is considered a typical phytoestrogen. It has either estrogenic or antiestrogenic effects that mainly depend on estrogen levels in vivo. This study investigated the effects and mechanisms of calycosin on estrogen receptor (ER)–positive human breast cancer (MCF-7) cells in vitro. Methods: ER-positive MCF-7 cells were treated with different concentrations of calycosin. Effects of calycosin on the proliferation of ER-positive MCF-7 cells were determined by the MTT assay. Apoptosis in these treated cells was examined by flow cytometry. The mRNA and protein levels of Bcl-2 and Bax in these treated cells were also determined by reverse-transcription polymerase chain reaction and immunohistochemical staining, respectively. Results: Compared with the vehicle control, calycosin stimulated proliferation of ER-positive MCF-7 cells at low concentrations (2, 4, and 8 µmol/L). Furthermore, at these concentrations, calycosin decreased the percentage of early apoptosis in MCF-7 cells, downregulated mRNA and protein levels of Bax, and upregulated those of Bcl-2 at low concentrations. On the other hand, calycosin at higher concentrations (16 and 32 µmol/L) inhibited cell proliferation. Conclusion: At relatively low concentrations, calycosin has stimulatory effects on the proliferation of MCF-7 cells, with the estrogenic effect the mechanism.