G P Zhang1, D Han, G Liu, S G Gao, X Q Cai, R H Duan, X S Feng. 1. Department of Oncology, Cancer Institute, First Affiliated Hospital of Henan University of Science and Technology, Luoyang, China.
Abstract
OBJECTIVE: Soy isoflavone is associated with modification of breast cancer risk. Effects of dietary isoflavone on breast tissue carcinogenesis under varying endogenous oestrogen contexts were investigated. METHODS: Five-week-old mouse mammary tumour virus (MMTV)-erbB2 female transgenic mice (n = 180) were divided into three equal groups: low-, normal- and high-oestrogen groups. Each group was then subdivided into an experimental group (given soybean feed) and a control group (given control feed). RESULTS: In the high-oestrogen environment, breast cancer incidence was significantly lower in the experimental versus the control group, whereas in the low-oestrogen environment, breast cancer incidence was significantly higher in the experimental versus the control group. There were no between-group differences in mean breast tumour latency, mean largest tumour diameter and breast tumour tissue vascular endothelial growth factor levels. CONCLUSIONS: Dietary soy isoflavones promote breast cancer at low oestrogen levels but inhibit breast cancer at high oestrogen levels. This effect may only occur during the initiation stage of breast cancer.
OBJECTIVE: Soy isoflavone is associated with modification of breast cancer risk. Effects of dietary isoflavone on breast tissue carcinogenesis under varying endogenous oestrogen contexts were investigated. METHODS: Five-week-old mouse mammary tumour virus (MMTV)-erbB2 female transgenic mice (n = 180) were divided into three equal groups: low-, normal- and high-oestrogen groups. Each group was then subdivided into an experimental group (given soybean feed) and a control group (given control feed). RESULTS: In the high-oestrogen environment, breast cancer incidence was significantly lower in the experimental versus the control group, whereas in the low-oestrogen environment, breast cancer incidence was significantly higher in the experimental versus the control group. There were no between-group differences in mean breast tumour latency, mean largest tumour diameter and breast tumour tissue vascular endothelial growth factor levels. CONCLUSIONS: Dietary soy isoflavones promote breast cancer at low oestrogen levels but inhibit breast cancer at high oestrogen levels. This effect may only occur during the initiation stage of breast cancer.