Project description:The present experiments were performed to determine the roles of estrogen receptors M-NM-1 and M-NM-2 (ERM-NM-1 and ERM-NM-2) in normal and neoplastic development in the mouse mammary gland. In wild-type mice, in vivo administration of estradiol (E) + progesterone (P) stimulated mammary ductal growth and alveolar differentiation. Mammary glands from mice in which the ERM-NM-2 gene has been deleted (M-NM-2ERKO mice) demonstrated normal ductal growth and differentiation in response to E + P. By contrast, mammary glands from mice in which the ERM-NM-1 gene has been deleted (M-NM-1ERKO mice) demonstrated only rudimentary ductal structures that did not differentiate in response to E + P. EGF demonstrates estrogen-like activity in the mammary glands of M-NM-1ERKO mice: treatment of M-NM-1ERKO mice with EGF + P (without E) supported normal mammary gland development, induced expression of progesterone receptor (PR), and increased levels of G- protein-coupled receptor (GPR30) protein. Mammary gland development in M-NM-2ERKO mice treated with EGF + P was comparable to that of wild-type mice receiving EGF + P; EGF had no statistically significant effects on the induction of PR or expression of GPR30 in mammary glands harvested from either wild-type mice or M-NM-2ERKO mice. In vitro exposure of mammary glands to 7,12-dimethylbenz[a]anthracene (DMBA) induced preneoplastic mammary alveolar lesions (MAL) in glands from wild-type mice and M-NM-2ERKO mice, but failed to induce MAL in mammary glands from M-NM-1ERKO mice. Microarray analysis of DMBA-treated mammary glands identified 28 functional pathways whose expression was significantly different in M-NM-1ERKO mice versus both M-NM-2ERKO and wild-type mice; key functions that were differentially expressed in M-NM-1ERKO mice included cell division, cell proliferation, and apoptosis. The data demonstrate distinct roles for ERM-NM-1 and ERM-NM-2 in normal and neoplastic development in the mouse mammary gland, and suggest that EGF can mimic the ERM-NM-1-mediated effects of E in this organ. Gene expression of mammary gland organ culture and DMBA-induced lesions from 4 mouse strains.

Project description:Clinical studies have revealed that social support improves the outcome of cancer patients while epidemiological studies suggest that social isolation increases the risk of death associated with several chronic diseases. However, the precise biological consequences of an unfavorable social environment have not been defined. To do so, robust, reproducible pre-clinical models are needed to study the mechanisms whereby an adverse environment impacts on gene expression and cancer biology. Because random assignment of inbred laboratory mice to well-defined social environments allows accurate and repeated measurements of behavioral and endocrine parameters, transgenic mice provide a pre-clinical framework with which to begin to determine gene-environment mechanisms. In this study, we found that female C3(1)/SV40 T-antigen mice deprived of social interaction from weaning exhibited increased expression of genes encoding key metabolic pathway enzymes in the pre-malignant mammary gland. Chronic social isolation was associated with upregulated fatty acid synthesis and glycolytic pathway gene expression - both pathways known to contribute to increased breast cancer growth. Consistent with the expression of metabolic genes, isolated mice subsequently developed significantly larger mammary gland tumors compared to group-housed mice. Endocrine evaluation confirmed that isolated mice developed a heightened corticosterone stress response compared to group-housed mice. Together, these transdisciplinary studies show for the first time that an adverse social environment is associated with altered mammary gland gene expression and tumor growth. Moreover, the identification of specific alterations in metabolic pathways favoring tumor growth suggests potential molecular biomarkers and/or targets (e.g. fatty acid synthesis) for preventive intervention in breast cancer. Experiment Overall Design: SV40 Tag mice we isolated or grouped at weaning. Mouse mammary glands were rapidly excised at necropsy and immediatley flash frozen to detect difference in gene expression between thoraci MG from isolated versus group-housed female mice.

Project description:Background: The differential expression pattern of microRNAs (miRNAs) during mammary gland development might provide insights into their role in regulating the homeostasis of the breast epithelium. Our aim was to analyse these regulatory functions by deriving a comprehensive tissue-specific combined miRNA and mRNA expression profile of post-natal mouse mammary gland development. We measured the expression of 318 individual murine miRNAs by bead-based flow-cytometric profiling of whole mouse mammary glands throughout a 16-point developmental time course, including juvenile, puberty, mature virgin, gestation, lactation, and involution stages. In parallel whole-genome mRNA expression data were obtained. Results: One third (n = 102) of all murine miRNAs analysed were present during mammary gland development. MicroRNAs were represented in seven temporally co-expressed clusters, which were enriched for both miRNAs belonging to the same family and breast cancer-associated miRNAs. Global miRNA and mRNA expression was significantly reduced during lactation and the early stages of involution after weaning. For most detected miRNA families we did not observe systematic changes in the expression of predicted targets. For miRNA families whose targets did show significant changes, we observed inverse patterns of miRNA and target expression. The datasets are made publicly available and the combined expression profiles represent an important community resource for mammary gland biology research. Conclusions: MicroRNAs were expressed in co-regulated clusters during mammary gland development. Breast cancer-associated miRNAs were significantly enriched in these clusters. The mechanism and functional consequences of this miRNA co-regulation and its correlation with mRNA expression provide new avenues for research into mammary gland biology and generates candidates for functional validation. Developmental time course over 17 time points with 2-3 independent biological replicates per time point and four pairs of technical replicates, 48 samples in total

Project description:This is a genome-wide approach to identifying genes persistently induced in the mouse mammary gland by acute whole body low dose ionizing radiation (10cGy), 1 and 4 weeks after exposure. Gene expression that is modified under these parameters were compared between Tgfb1 wild type and heterozygote littermates in order to determine which genes induced or repressed by radiation were mediated via Tgfb1 status. Differential gene expression was analyzed in Tgfb1 heterozygote and wild type littermate 4th mammary glands, after whole body exposure to an acute dose of 10cGy ionizing radiation. Estrus cycle was normalized in all mice two days prior to irradiation by injection with an estrogen and progesterone mixture. It is widely believed that the carcinogenic action of ionizing radiation is due to targeted DNA damage and resulting mutations, but there is also substantial evidence that non-targeted radiation effects alter epithelial phenotype and the stromal microenvironment. Activation of transforming growth factor beta 1 (TGFbeta) is a non-targeted radiation effect that mediates cell fate decisions following DNA damage and regulates microenvironment composition; it could either suppress or promote cancer. Gene expression profiling shown herein demonstrates that low dose radiation (10 cGy) elicits persistent changes in Tgfb1 wild type and heterozygote murine mammary gland that are highly modulated by TGFbeta. We asked if such non-targeted radiation effects contribute to carcinogenesis by using a novel radiation chimera model. Unirradiated Trp53 null mammary epithelium was transplanted to the mammary stroma of mice previously exposed to a single low (10 -100 cGy) radiation dose. By 300 days, 100% of transplants in irradiated hosts at either 10 or 100 cGy had developed Trp53 null breast carcinomas compared to 54% in unirradiated hosts. Tumor growth rate was also increased by high, but not low, dose host irradiation. In contrast, irradiation of Tgfb1 heterozygote mice prior to transplantation failed to decrease tumor latency, or increase growth rate at any dose. Host irradiation significantly reduced the latency of invasive ductal carcinoma compared to spindle cell carcinoma, as well as those tumors negative for smooth muscle actin in wild type but not Tgfb1 heterozygote mice. However, irradiation of either host genotype significantly increased the frequency of estrogen receptor negative tumors. These data demonstrate two concepts critical to understanding radiation risks. First, non-targeted radiation effects can significantly promote the frequency and alter the features of epithelial cancer. Second, radiation-induced TGFbeta activity is a key mechanism of tumor promotion. Keywords: Differential gene expression after low dose irradiation Two genotypes: TGBbeta1 heterozygote and wildtype mouse mammary glands. Two time points post-10cGy-irradiation per genotype (1 week, 4 weeks); control time point was 1 week post-sham-irradiation. Two or three replicates per time point.

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Mouse adult mammary development

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