Tangeretin inhibits the proliferation of human breast cancer cells via CYP1A1/CYP1B1 enzyme induction and CYP1A1/CYP1B1–mediated metabolism to the product 4′ hydroxy tangeretin
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Abstract
Tangeretin is a polymethoxylated flavone with multifaceted anticancer activity. In the present study, the metabolism and further antiproliferative activity of tangeretin was evaluated in the CYP1 expressing human breast cancer cell lines MCF7 and MDA–MB–468 and the normal breast cell line MCF10A. Tangeretin was converted to 4ʹ OH tangeretin by recombinant CYP1 enzymes and in MCF7 and MDA–MB–468 cells. This metabolite was absent in MCF10A cells that did not express CYP1 enzymes. Tangeretin exhibited submicromolar IC50 (0.25±0.15 μM) in MDA–MB–468 cells, whereas it was less active in MCF7 cells (13.5±0.8 μM) and completely inactive in MCF10A cells (>100 μM). In MDA–MB–468 cells that were coincubated with the CYP1 inhibitor acacetin, an approximately 70–fold increase was noted in the IC50 (18±1.6 μM) of tangeretin. In the presence of the CYP1 inhibitor acacetin, the conversion of tangeretin to 4ʹ OH tangeretin was significantly reduced in MDA–MB–468 cells (2.55±0.19 μM vs. 6.33±0.12 μM). The mechanism of antiproliferative action involved cell cycle arrest at the G1 phase for MCF7 and MDA–MB–468 cells, whereas the cell cycle of MCF10A cells was unaffected by 10 μM of tangeretin treatment for 24 and/or 48 h. Tangeretin was further shown to induce CYP1 enzyme activity and CYP1A1/CYP1B1 protein expression in MCF7 and MDA–MB–468 cells. Taken collectively, the results suggest that tangeretin inhibits the proliferation of human breast cancer cells via CYP1A1/CYP1B1 enzyme induction and CYP1A1/CYP1B1–mediated metabolism to the product 4ʹ hydroxy tangeretin.