Effects of soy isoflavone extracts on the growth of estrogen-dependent human breast cancer (MCF-7) tumors implanted in ovariectomized nude mice

In this study,we explored the effects of soy isoflavone extracts on the growth of estrogen-dependent human breast cancer (MCF-7) tumors implanted in ovariectomized athymic mice. The ovariectomized athymic mice were implanted with MCF-7 cells. They were fed with low,moderate and high doses of soy isoflavone extracts,at dietary concentrations of 6.25,12.5 and 25 g/kg,respectively. The expression of ki-67 was detected by immunohistochemistry. The pS2 expression in tumors was analyzed by real-time PCR. Estrogen level in the serum was measured by chemiluminescence enzyme immunoassay. Com-pared with the control group,dietary soy isoflavone extracts had a significant stimulatory effect on MCF-7 tumor growth in mice (P < 0.05). The ki-67 and pS2 mRNA expressions in tumors were signifi-cantly increased by 6.25 and 12.5 g/kg dose of soy isoflavone extracts (P < 0.05). And,estrogen level in serum of 6.25 and 12.5 g/kg dose groups was higher than that of control group (P > 0.05). In conclusion,in the tested dietary concentration range soy isoflavone extracts had a stimulatory effect on tumor growth. 6.25 and 12.5 g/kg doses of soy isoflavone extracts can increase the cell proliferation in tumors and induce estrogen-responsive pS2 expression.