The developing fetus is uniquely sensitive to long-term imprinting effects of estrogenic chemicals that are known to have profound effects on adult disease susceptibility. Genistein, a naturally occurring isoflavone found in soy, is recognized as a dietary estrogen as it interacts with both estrogen receptor (ER)-alpha and ER-beta. Human exposure to genistein is predominantly through dietary consumption of soy products, however, its use as nutritional supplements and pharmaceutical agents has dramatically increased due to the presumed beneficial effects of phytoestrogens in preventing cardiovascular diseases and cancer. Ironically, the potential deleterious effects of dietary estrogens, especially if exposure occurs during critical stages of development, remain poorly understood. Of concern are the well-documented carcinogenic effects of prenatal exposure to diethylstilbestrol (DES) and the wide exposure of infants and children to soy-based formulas. We have developed a mouse model to investigate the potential adverse effects of exposing the developing routine neonate to genistein. Outbred female CD-1 mice were treated on days 1-5 with equivalent estrogenic doses of genistein (50 mg/kg/day) or DES (0.001 mg/kg/day) dissolved in corn oil, or corn oil alone (control), and sacrificed at varying ages. A 35% and 31% incidence of uterine adenocarcinoma were found in aged mice neonatally treated with genistein (50 mg/kgf day) and DES (0.001mg/kg/day), respectively. A higher dose of DES (lmg/kg/day) caused a 95% incidence of the cancer. In this proposal, we will test the hypothesis that neonatal exposure to estrogenic compounds induces 1) aberrant methylation of 5'CpG islands of specific genes, and 2) that these changes persist in adult uterine tissues leading to """"""""permanent"""""""" changes in gene expression profiles in the adult uterus, resulting in a higher propensity for uterine tumorigenesis in this mouse model.
In Aim 1, we will use a highly innovative technology (methylation-sensitive DNA fingerprinting or MS-AP-PCR) to identify genes that are hyper- or hypomethylated in neonatal and adult uteri from mice neonatally exposed to DES or genistein as compared to control (unexposed) animals.
In Aim 2, we will perform global gene profiling analyses to identify gene sets that are up - or down - regulated in adult uteri from animals exposed neonatally to estrogens when compared to those without exposure. By comparing the results obtained from Aim 1 and Aim 2 we expect to establish a link between hyper- (silencing) or hypo- (release from silencing) of specific genes induced by neonatal estrogen exposure that are of relevancy to cancer susceptibility and development in the adult uteri, Results from these studies are expected to enhance our understanding of the mechanistic basis of adult diseases caused by developmental exposure to dietary estrogens. Future studies along this line of investigation will address impacts of other environmental estrogens.
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