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.

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. 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. 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. At relatively low concentrations, calycosin has stimulatory effects on the proliferation of MCF-7 cells, with the estrogenic effect the mechanism.