Germacrone Inhibits Estrogen Receptor α-Mediated Transcription in MCF-7 Breast Cancer Cells

Estrogen receptor (ER) alpha-positive breast cancer cells regulate the expression of estrogen-responsive genes, which are involved in cell proliferation, differentiation, and cell cycle progression. Clinically, the inhibition of ER alpha-mediated gene expression in breast cancer cells has long been considered an effective way to prevent the development and progression of cancer. Germacrone, a terpenoid compound isolated from Rhizoma curcuma, has been known to have antitumor activity in various human cancer cell lines. However, the mechanism by which germacrone inhibits the proliferation of breast cancer cells is still unclear. Here, we demonstrated that germacrone inhibits ER alpha-mediated gene expression at the transcriptional level in MCF-7 cells. Germacrone inhibits the recruitment of ER alpha to the estrogen response element on chromatin and consequently compromises the binding of switch/sucrose non-fermentable chromatin remodeling complex and RNA polymerase II to target gene promoter, thereby inhibiting the estrogen-induced chromatin accessibility. In addition, germacrone efficiently potentiates the antitumor activity of methotrexate and 5-fluorouracil. Our results not only provide substantial molecular mechanism of germacrone on ER alpha-mediated signaling in breast cancer cells but also demonstrate the benefits of germacrone as a combination therapy with other drugs for the treatment of breast cancer. Copyright (C) 2016 John Wiley & Sons, Ltd.