NEONATAL GENISTEIN CHEMOPREVENTS MAMMARY-CANCER

We have investigated the potential of genistein, an estrogenic compone nt of soy, when administered neonatally, to manifest a protective effe ct against chemically induced mammary cancer. Female Sprague-Dawley ra ts were treated on Day 2, 4, and 6 postpartum with genistein or dimeth ylsulfoxide (vehicle). To induce mammary carcinogenesis, all animals w ere subsequently exposed on Day 50 postpartum to dimethylbenz(a)anthra cene. Animals treated neonatally with genistein had increased latency and reduced incidence and multiplicity of mammary tumors compared with vehicle-treated animals. Cell differentiation studies in mammary whol e mounts revealed that neonatal genistein treatment resulted in decrea sed numbers of terminal end buds and increased numbers of lobular stru ctures. A precocious maturation of undifferentiated terminal end buds to more differentiated lobules may account for neonatal genistein trea tment protecting against chemically induced mammary cancer.