Inhibition of cell growth by BrMC through inactivation of Akt in HER-2/neu-overexpressing breast cancer cells.

We previously reported that chrysin (ChR) and its analogs induced cell cycle arrest and apoptosis in human estrogen receptor-positive/-negative breast cancer cells. However, it was unknown whether 8-bromo-7-methoxychrysin (BrMC), a novel synthetic ChR analog, inhibited the cell growth of human epidermal growth factor receptor 2 (HER-2)/neu-overexpressing breast cancers. In the present study, it was demonstrated that BrMC preferentially inhibited the cell viability of HER-2/neu-overexpressing MDA-MB-453 and BT-474 cells. Western blot analysis revealed that HER-2/neu expression and tyrosine phosphorylation were inhibited by BrMC in a concentration-dependent manner; whereas the proteasome inhibitor, MG-132, significantly prevented BrMC-induced HER-2/neu depletion and cell death in MDA-MB-453 cells. This directly indicated that BrMC-induced HER-2/neu depletion and cell growth inhibition was mediated by a proteasomal pathway. BrMC significantly downregulated the expression of cyclin D1, cyclin E and CDK4, followed by the suppression of protein kinase B phosphorylation and downstream effectors, GSK-3β and β-catenin. A colony formation assay also confirmed the growth-inhibitory effects of BrMC. Thus, these findings clearly demonstrate the anticancer activity of BrMC against human HER-2/neu-overexpressing breast cancer cells. Thus, these findings clearly demonstrate the anticancer activity of BrMC against human HER 2/neu-overexpressing breast cancer cells, and highlight BrMC as a promising candidate for breast cancer therapy.