Abstract
Natural compounds derived from plants have been an important source of numerous clinically useful anticancer agents. Nevertheless, limited studies indicate that xanthohumol (XN), a major prenylated flavonoid in hop plants (Humulus lupulus), may possess anticarcinogenic properties. The purpose of the present study was to clarify the antitumorigenic effects and the underlying mechanism of XN on breast cancer in vivo and in vitro. A 4T1 breast tumor mouse model was used in the present study to investigate XN suppression of tumor growth as detected by tumorigenicity assays in vivo. In addition, in vitro studies revealed that XN significantly decreased cell viability, induced G0/G1 cell cycle arrest and apoptosis in MCF-7 and MDA-MB-231 cells, as confirmed by an MTT assay, flow cytometry and western blot analysis, indicating anticarcinogenic activity of XN against breast cancer. Furthermore, immunohistochemistry was performed to confirm the inactivation of the Notch signaling pathway, Notch 1 and Ki-67, in vivo; consistently, XN caused decreased activation of the Notch signaling pathway and apoptotic regulators B-cell lymphoma-2 (Bcl-2), Bcl-extra large and caspase 3, as determined by western blot analysis in vitro. This study suggests that XN may potentially be useful as a chemopreventive agent during breast hyperplasia and carcinogenesis, acting via the regulation of Notch associated apoptotic regulators in vivo and in vitro.