Ginkgetin induces cell death in breast cancer cells via downregulation of the estrogen receptor

Ginkgetin is a natural biflavonoid isolated from the leaves of Ginkgo biloba, and is characterized by its anti-inflammatory and anti-viral activities. Although numerous studies state that it has also antitumor activity, the anti-proliferative effect of ginkgetin and the underlying mechanism in breast cancer cells have not yet been investigated. In the present study, ginkgetin inhibited the cell viability of MCF-7 and T-47D cells dose-dependently, and suppressed the expression of the estrogen receptor (ER) at the mRNA and protein levels. Among the targets of the ER, 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase 3 (PFKFB3), cyclin D1 and survivin were also downregulated by ginkgetin treatment. The anti-proliferative effects of ginkgetin were sufficient to suppress the growth by estradiol stimulation. However, ginkgetin did not significantly affect the viability of MDA-MB-231 cells, which are ER-negative cells. Furthermore, the knockdown of the ER and an inhibitor of PFKFB3 significantly sensitized MCF-7 and T-47D cells to ginkgetin. These findings suggest that ginkgetin induces cell death in ER-positive breast cancer cells via the inhibition of ER expression and that it is a promising agent for breast cancer treatment.