Anti-breast cancer potential of daidzein in rodents

Aims: This study was carried out to explore anti-breast cancer potential of isoflavone daidzein or its related compounds using appropriate animal models and their anti-tumor mechanism. Main methods: Daidzein or its major metabolite equol at a dose molar equivalent to tamoxifen [1.0 mg (2.7 mu mol)/kg or 10 mg (27 mu mol)/kg/day] was treated orally to rats bearing 7,12-dimethylbenz(a)anthracene (DMBA)-induced mammary tumors or ovariectomized athymic nude mice implanted with human MCF-7 breast cancer xenograft and an estrogen pellet. The growth of tumors was monitored for several weeks after the treatment. The cell-cycle and apoptotic stages in mammary tumors collected from rats were analyzed by now cytometry. Immunohistochemistry analysis was also used to determine the expression of caspase-3. Key findings: Oral treatment with daidzein or equol at a human equivalent dose suppressed the growth of both DMBA-induced mammary tumors and human MCF-7 breast cancer xenografts in rodents, the inhibitory activity being superior to that of genistein or tamoxifen. Strong apoptosis induced by daidzein or equol contributes to the anti-tumor potential. Significance: Daidzein and its metabolite equol showed the potential of inhibiting the growth of mammary tumors in rodents. Daidzein or equol could be used as a core structure to design new drugs for breast cancer therapy. Our results indicate that consumption of daidzein may protect against breast cancer. (c) 2012 Elsevier Inc. All rights reserved.