Uterine adenocarcinoma in mice treated neonatally with genistein

The developing fetus is uniquely sensitive to perturbation with estrogenic chemicals. The carcinogenic effect of prenatal exposure to diethylstilbestr ol (DES) is the classic example, Because phytoestrogen use in nutritional a nd pharmaceutical applications for infants and children is increasing, we i nvestigated the carcinogenic potential of genistein, a naturally occurring plant estrogen in soy, in an experimental animal model previously reported to result in a high incidence of uterine adenocarcinoma after neonatal DES exposure. Outbred female CD-1 mice were treated on days 1-5 with equivalent estrogenic doses of DES (0.001 mg/kg/day) or genistein (50 mg/kg/day), At 18 months, the incidence of uterine adenocarcinoma was 35% for genistein an d 31% for DES, These data suggest that genistein is carcinogenic if exposur e occurs during critical periods of differentiation. Thus, the use of soy-b ased infant formulas in the absence of medical necessity and the marketing of soy products designed to appeal to children should be closely examined.