Ginsenoside Rh2 inhibits breast cancer cell growth via ER beta-TNF alpha pathway

Ginsenoside Rh2 is one of rare panaxidiols extracted from Panax ginseng and a potential estrogen receptor ligand that exhibits moderate estrogenic activity. However, the effect of Rh2 on growth inhibition and its underlying molecular mechanism in human breast cells are not fully understood. In this study, we tested cell viability by MTT and colony formation assays. Cell growth and cell cycle were determined to investigate the effect of ginsenoside Rh2 by flow cytometry. The expressions of estrogen receptors (ERs), TNF alpha, and apoptosis-related proteins were detected by qPCR and western blot analysis. The mechanisms of ER alpha and ER beta action were determined using transfection and inhibitors. Antitumor effect of ginsenoside Rh2 against MCF-7 cells was investigated in xenograft mice. Our results showed that ginsenoside Rh2 induced apoptosis and G1/S phase arrest in MCF-7 cells. Treatment of cells with ginsenoside Rh2 down-regulated protein levels of ER alpha, and up-regulated mRNA and protein levels of ER beta and TNF alpha. We also found that ginsenoside Rh2-induced TNF alpha over-expression is through up-regulation of ER beta initiated by ginsenoside Rh2. Furthermore, ginsenoside Rh2 induced MCF-7 cell apoptosis via estrogen receptor beta-TNF alpha pathway in vivo. These results demonstrate that ginsenoside Rh2 promotes TNF alpha-induced apoptosis and G1/S phase arrest via regulation of ER beta.