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SECOND INTERNATIONAL SYMPOSIUM
ON THE ROLE OF SOY
IN PREVENTING AND TREATING CHRONIC DISEASESeptember 15-18, 1996
Brussells, Belgium
SCIENTIFIC PROGRAM
(Oral Abstracts)Soy and Cancer
Soy Consumption and Cancer Risk : Human StudiesThe Effects of Soy Supplementation on Epithelial Proliferation in The Normal Human Breast
1McMichael-Phillips, D.F., 2Harding, C., 3Morton, M., 1Potten, C.S. and 2Bundred, N.J.1Dept. Epithelial Biology, Paterson Institute for Cancer Research, Christie Hospital NHS Trust, Manchester, M20 9BX. 2Dept. Surgery, University Hospital of South Manchester, Manchester, M20 8LR. 3Tenovus Institute, UWCM, Cardiff, CF4 4XX. 4Dept. Medical Oncology, Christie Hospital NHS Trust, Manchester. M20 9BX.
A high dietary intake of soy (i.e., in Japan and Singapore) has been associated with a reduction in the incidence of breast cancer in premenopausal women. Phytoestrogens present in soy inhibit human breast cancer cell proliferation in vitro and breast cancer development in animal models, but no data exist for their effects on the normal human breast. The aim of this study was to examine the effect of dietary soy supplementation on the proliferation rate of premenopausal normal breast epithelium. Women (n=29) with benign or malignant breast disease were randomized either to placebo or to 60g soy (containing 45mg isoflavones) supplement taken daily over 14 days. Biopsies of normal breast were labeled with 3H thymidine to detect the number of cells in S-phase and immunocytochemically stained for the proliferation antigen, Ki67. The phytoestrogens genistein, daidzein, equol, enterolactone and enterodiol were measured in serum and urine samples obtained from women before and after supplementation. Levels of the isoflavones, genistein and daidzein increase significantly (p=<0.01) in the soy group at 14 days. Results show a strong correlation between the Ki67 and thymidine labeling index (TLI, P=0.9492, P=<0.001). A significant increase in the proliferation rate of breast lobular epithelium after 14 days soy supplementation, when both day of cycle and age of patient were taken into consideration has been demonstrated (p=0.01). Short-term dietary soy stimulates breast proliferation (perhaps acting as an oestrogen agonist) and further studies are required to determine the effect of long-term supplementation on the pituitary gland and breast.
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