Differences in the mechanisms of action of BDE-47 and its metabolites on OVCAR-3 and MCF-7 cell apoptosis.

Data concerning possible carcinogenic action of polybrominated diphenyl ethers (PBDEs) in hormone-dependent tissues are limited. Our earlier studies showed that 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) stimulated OVCAR-3 and MCF-7 cell proliferation, while its hydroxylated metabolites (5-OH-BDE-47 and 6-OH-BDE-47) increased estrogen receptors protein expression and extracellular signal-regulated kinase 1/2 and protein kinase Cα phosphorylation in these cell lines. In addition to cell proliferative disorder, a failure in the regulation of apoptosis can also lead to the formation and development of tumors. Therefore, in the present study, we investigated the effect of BDE-47 and its metabolites (2.5-50 ng ml-1 ) on the expression of apoptosis regulatory genes and proteins, caspase-8 and -9 activity and DNA fragmentation induced by extracellular signal-regulated kinase inhibitor (PD098059) and protein kinase Cα inhibitor (Gӧ 6976) in ovarian (OVCAR-3) and breast (MCF-7) cancer cells. In OVCAR-3 cells, BDE-47 upregulated expression of most of the investigated genes and increased protein expression of tumor necrosis factor (TNF)-α, TNF receptor 1, caspase-6, Bcl-xl and caspase-8 activity. Whereas in MCF-7 cells, BDE-47 resulted in the downregulation of most of the investigated genes, and decreased caspase-8 and -9 activity. In both OVCAR-3 and MCF-7 cells, the expression of most of the investigated genes were downregulated by metabolites. Exposure of OVCAR-3 cells to 5-OH-BDE-47 corresponded with a decrease in the protein expression of caspase-6, caspase-9 and Bcl-xl and treatment with 6-OH-BDE-47 decreased Bcl-xl and TNF receptor 1 expression in OVCAR-3 cells and caspase-9 expression in MCF-7 cells. Hydroxylated metabolites of BDE-47 have strong inhibitory effects on apoptosis in ovarian and breast tumor cells and thus should be considered potential carcinogens in hormone-dependent cancers. Copyright © 2016 John Wiley & Sons, Ltd.