Abstract 3700: Prepubertal dietary genistein intake reduces ovarian cancer risk in BRCA+/- mice

Genistein, a soy-derived isoflavone, is thought to play a key role in the cancer-preventive activity of soy consumption. Germline mutations in BRCA1 and BRCA2 genes are known risk factors for both ovarian and breast cancers. Previously, our lab has discovered that prepubertal dietary exposure to genistein reduced 7,12-dimethylbenz(a)anthracene (DMBA)-induced mammary incidence (P = 0.029) and aggressiveness of the tumors (P < 0.001) in the WT mice, and upregulated the expression of BRCA1 in their mammary glands (P = 0.04). In this study, we investigated whether prepubertal dietary exposure to genistein reduces ovarian tumors in heterozygous BRCA+/- mice and their wild type littermates. Mice were fed a control diet AIN93G or 500 ppm genistein-supplemented diet from postnatal day (PND) 15 to PND 30, and thereafter mice received the control AIN93G diet. On PND42, control and genistein mice were primed with medroxyprogesterone acetate and, starting at PND50, administered 7,12-dimethylbenz(a)anthracene (DMBA) once a week for four weeks. Ovarian tissues were harvested at 5 months of age. Histopathology assessment shows that mice developed granulosa cell tumors. Ovarian tumor incidence in control diet fed wildtype mice was 80% and in the BRCA+/- mice 100%. The incidence dropped to 33% in the wildtype and to 50% in the BRCA+/- mice following prepubertal genistein intake. Thus, the exposure to prepubertal genistein in both BRCA+/- and WT mice significantly reduced ovarian tumor incidence, compared with their control diet fed littermates (P=0.001). The mechanisms mediating the protective effect of prepubertal genistein intake on ovarian cancer risk are being investigated.

Citation Format: E Carney, L. Hilakivi-Clarke, A. Warri, S. de Assis. Prepubertal dietary genistein intake reduces ovarian cancer risk in BRCA+/- mice. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3700. doi:10.1158/1538-7445.AM2013-3700

In utero alcohol exposure increases mammary tumorigenesis in rats

Findings in humans and animal models suggest that in utero hormonal and dietary exposures increase later breast cancer risk. Since alcohol intake by adult women consistently increases their breast cancer risk, we wondered whether maternal alcohol consumption during pregnancy increases female offspring's mammary tumorigenesis. In our study, pregnant female rats were pair-fed isocaloric diets containing either 0 (control), 16 or 25 g alcohol kg(-1) feed between days 7 and 19 of gestation. These alcohol exposures generate blood alcohol levels that correspond to low and moderate alcohol consumption and are lower than those that induce foetal alcohol syndrome. Serum oestradiol levels were elevated in pregnant rats exposed to alcohol (P<0.003). When adult, female offspring of alcohol-exposed dams developed significantly more 7,12-dimethylbenz[a]anthracene -induced mammary tumours, compared to the controls (tumour multiplicity; mean+/-s.e.m., controls: 2.0+/-0.3, 16 g alcohol: 2.7+/-0.4 and 25 g alcohol: 3.7+/-0.4; P<0.006). In addition, the mammary epithelial tree of the alcohol-exposed offspring was denser (P<0.004) and contained more structures that are susceptible for the initiation of breast cancer (P<0.001). Immunohistochemical assessment indicated that the mammary glands of 22-week-old in utero alcohol-exposed rats contained elevated levels of oestrogen receptor-alpha (P<0.04) that is consistent with the changes in mammary gland morphology. In summary, maternal alcohol intake during pregnancy increases female offspring's mammary tumorigenesis, perhaps by programming the foetal mammary gland to exhibit persistent alterations in morphology and gene expression. It remains to be determined whether an increase in pregnancy oestradiol levels mediated alcohol's effects on offspring's mammary tumorigenesis.

Maternal high n-6 polyunsaturated fatty acid intake during pregnancy increases voluntary alcohol intake and hypothalamic estrogen receptor alpha and beta levels among female offspring

Identification of nongenetic biological factors that predispose to alcohol abuse is central to attempts to prevent alcoholism. Since an exposure to estradiol in utero increases voluntary alcohol intake in adulthood, we investigated whether an increase in pregnancy estradiol levels, caused by feeding pregnant mice a high-fat corn oil diet, also influences voluntary alcohol intake among female offspring. In addition, the effect on estrogen receptor alpha (ER-alpha) and ER-beta protein levels in the brain using Western blot assay, was determined. Pregnant CD-1 mice were kept on a high n-6 polyunsaturated fatty acid (PUFA; 43% calories from corn oil) or low n-6 PUFA diet (16% calories from corn oil) throughout gestation, and switched to a Purina laboratory chow after the pups were born. When 4 months of age, the female offspring were given a choice between 5% alcohol and tap water. The offspring of high n-6 PUFA mothers voluntarily consumed more alcohol than the offspring of low n-6 PUFA mothers. ER-alpha and ER-beta protein levels in the hypothalamus were 1.5- and 2-fold higher, respectively, in the female offspring of high n-6 PUFA mothers than in the low n-6 PUFA offspring. No significant changes in the protein levels of ER-alpha and ER-beta were seen in the frontal brain. Our findings indicate that a maternal exposure to a high n-6 PUFA diet during pregnancy increases alcohol intake among female offspring. This behavioral change, together with previously observed increase in aggressiveness and reduction in depressive-like behavior in these offspring, may be linked to an increase in the hypothalamic ER-alpha and ER-beta levels.