Effects of Combined Soy Isoflavone Extract and Docetaxel Treatment on Murine 4T1Breast Tumor Model

Emergence of drug resistance has brought major problems in chemotherapy. Using nutrients in combination with chemotherapy could be beneficial forimprovement of sensitivity of tumors to drug resistance. Soybean-derived isoflavones have been suggested as chemopreventive agents for certain types of cancer, particularlybreast cancer. In this study, the synergistic effects of soy isoflavone extract in combination with docetaxel in murine 4T1 breast tumor model were investigated. In this study, mice were divided into 4 groups (15 mice per group) of control, the dietary Soy Isoflavone Extract (SIE, 100 mg/kg diet), the Docetaxel (DOCE, 10 mg/kg) injection and the combination of dietary soy isoflavone extract and intravenousdocetaxel injection (DOCE+SIE). After 3 injections of docetaxel (once a week), 7 mice were sacrificed to analyze MKI67 gene and protein expressions and the rest weremonitored for diet consumption, tumor growth and survival rates. In DOCE+SIE group, diet consumption was significantly higher than DOCE group. While lifespan showed a trend towards improvement in DOCE+SIE group, nosignificant difference was observed among the 4 studied groups. Tumor volume was not significantly affected in treated groups. A lower but not significant MKI67 protein expression was detected in western blot in DOCE+SIE group. The mRNA expression was not significantly different among groups. The results suggest that the combination of soy isoflavone as an adjunct to docetaxel chemotherapy can be effective in improving diet consumption in breast cancer.