Danshen extract inhibits proliferation of breast cancer cells via modulation of Akt activity and p27 level

Abstract

Danshen (Salvia miltiorrhiza) is widely used in traditional Chinese medicine, often in combination with other herbs. Remedies containing Danshen extracts are used traditionally to treat a diversity of ailments, particularly cardiac and vascular disorders such as atherosclerosis or blood clotting abnormalities. In an attempt to check the effect of Danshen extract on proliferation of breast cancer cells, we treated Danshen extract to human breast cancer cell line, MCF-7 cells (HER2 low) and MCF-7 HER2 cells which were engineered to express HER2 using retroviral expression vector. HER2 is a transmembrane receptor tyrosine kinase and normally involved in the signal transduction pathways leading to tumor cell proliferation. MTT (3-(4,5-dimethylthiazol-2-yl)2,5-diphenyltetrazolium bromide) assays and cell proliferation assays revealed that Danshen extract strongly inhibited proliferation of both MCF-7 vec (vector control) cells and MCF-7 HER2 cells. Flow cytometry analyses indicated that Danshen treatment induces cell cycle delay in G1 phase. Forced expression of HER2 was shown to confer resistance to Danshen-induced inhibition of cell proliferation and cell cycle delay, suggesting that oncogenic HER2 is responsible for the resistance to pharmacological effect of Danshen. Western blot analyses showed that Danshen treatment induced down-regulation of Akt phosphorylation and increase in protein level of p27 both in MCF-7 vec and MCF-7 HER2 cells. Nevertheless, MCF-7 HER2 cells were more resistant to Danshen-induced inhibition of Akt phosphorylation and p27 up-regulation.