Shugan Liangxue Decoction (舒肝凉血方) Down-Regulates Estrogen Receptor α Expression in Breast Cancer Cells

Objective To observe the effect of Shugan Liangxue Decoction (舒肝凉血方, SGLXD) on estrogen receptor α (ERα) in human breast cancer cells. Methods The effect of SGLXD (0.85–5.10 mg/mL) on the proliferation of breast cancer cells were evaluated by 3-(4,5-dimethyl-2-thiazolyl)-2,5-diphenyl-2-H-tetrazolium bromide (MTT) assay. The nuclear ERα protein levels in MCF-7, T47D and ZR-75-1 cells which treated by SGLXD for 24 h were examined by western blot and immunofluorescence assay. MCF-7 and MDA-MB-231 cells were treated by 17β-estradiol (E2) with or without SGLXD, for 24 h, and the E2 targeted genes c-myc and bcl-2 protein product was evaluated by western blot. Results SGLXD showed dose-dependent inhibition on the proliferation of MCF-7, T47D and ZR-75-1 cells, but did not inhibit the proliferation of MDA-MB-231 cells. Furthermore, the promotive effect on cell growth induced by E2 was also significantly inhibited by SGLXD treatment. With the treatment of 1.70, 3.40, 5.10 mg/mL SGLXD, the nuclear ERα protein level was reduced to 88.1%, 70.4% and 60.9% in MCF-7 cells, and was decreased to 43.0%, 38.4% and 5.9% in ZR-75-1 cells as compared with the control group. In T47D cells, the nuclear ERα protein was down-regulated to 51.3% and 4.3% by 3.40 and 5.10 mg/mL SGLXD treatment. The down-regulative effect of SGLXD on nuclear ERα was confirmed by immunofluorescence assay. SGLXD decreased the protein product of c-myc and bcl-2. Conclusions SGLXD may exhibit selective inhibition effect on the proliferation of ER positive breast cancer cells. SGLXD reduced the nuclear ERα expression and the protein product of E2 target gene c-myc and bcl-2.