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Mammary Gland Morphological and Gene Expression Changes Underlying Pregnancy Protection of Breast Cancer Tumorigenesis

ABSTRACT: Pregnancy has been shown to decrease the risk of mammary carcinogenesis in human rretrospective epidemiological studies. In rodents, pregnancy prior to carcinogen administration or after carcinogen challenge has also been shown to reduce the incidence of palpable carcinomas. In this study our objective to determine the underlying genomic signature of the pregnancy and reproductive hormones on the mammary gland that contribute to the protection against mammary gland carcinogenesis. We used the rat microarray technology to observe total transcriptome changes after the pregnancy and exogenous reproductive hormone stimulation of the mammary gland.

ORGANISM(S): Rattus norvegicus

PROVIDER: GSE32125 | GEO | 2011/09/15

SECONDARY ACCESSION(S): PRJNA147429

REPOSITORIES: GEO

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Mammary Gland Morphological and Gene Expression Changes Underlying Pregnancy Protection of Breast Cancer Tumorigenesis

Project description:Pregnancy has been shown to decrease the risk of mammary carcinogenesis in human rretrospective epidemiological studies. In rodents, pregnancy prior to carcinogen administration or after carcinogen challenge has also been shown to reduce the incidence of palpable carcinomas. In this study our objective to determine the underlying genomic signature of the pregnancy and reproductive hormones on the mammary gland that contribute to the protection against mammary gland carcinogenesis. We used the rat microarray technology to observe total transcriptome changes after the pregnancy and exogenous reproductive hormone stimulation of the mammary gland. Fifteen 3 month old post-pubertal virgin Lewis rats were randomly assigned to three groups (5 rats per group): control (C), pregnancy (P) and hormone treatment (H). The P group animals had a full-term pregnancy (21-23 days) and rats in the group H were implanted subcutaneously on the dorsal midline with two silastic capsules [(0.078 inch inner diameter, 0.125 inch outer diameter) x 2 cm long; Dow Corning, Midland, MI) filled separately with 100 μg ethynyl estradiol (Sigma, St. Louis, MO) packed in a cellulose matrix (Sigma) and 30 mg of megesterol acetate (Sigma) for 21 days. The control animals had neither the hormone treatment nor being pregnant. The animals in C and P groups were also implanted with sham capsules filled with cellulose matrix only. The capsules were surgically implanted at the beginning of the experiment and removed from all animals after 21 days except that the capsules were removed from the P group following parturition (21-23 days). The delivered pups in the P group were euthanized within 4-6 hours of delivery to avoid suckling. After the removal of capsules all groups were rested a total of ~49 days before euthanasia. All animals were euthanized during metestrus stage, determined by vaginal cytology and total RNA was extracted from the mammary gland tissues using Trizol reagent.

2011-09-14 | E-GEOD-32125 | biostudies-arrayexpress

An epigenetic memory of pregnancy in the mouse mammary gland

2015-05-15 | GSE67386 | GEO

Pregnancy-associated alterations in DNA methylation patterns of mammary epithelial stem cells [reproductive stages]

Project description:Mammary gland development and luminal differentiation occur largely postnatally during puberty and pregnancy. We found that pregnancy had the most significant effects on stem cells, inducing a distinct epigenetic state that remained stable through life. Mammary glands were collected from different reproductive stages to purify different epithelium cell types, which were used for RNA extraction and hybridization on Affymetrix microarrays.

2015-01-22 | E-GEOD-54147 | biostudies-arrayexpress

An epigenetic memory of pregnancy in the mouse mammary gland

Project description:Pregnancy is the major modulator of mammary gland activity. It induces a tremendous expansion of the mammary epithelium and the generation of alveolar structures for milk production. Anecdotal evidence from multiparous humans indicates that the mammary gland may react less strongly to the first pregnancy than it does to subsequent pregnancies. Here we verify that the mouse mammary gland responds more robustly to a second pregnancy, indicating that the gland retains a long-term memory of pregnancy. A comparison of genome-wide profiles of DNA methylation in isolated mammary cell types revealed substantial and long lasting alterations. The majority of these alterations affect sites occupied by the Stat5a transcription factor and mark specific genes that are upregulated during pregnancy. We postulate that the epigenetic memory of a first pregnancy primes the activation of gene expression networks that promote mammary gland function in subsequent reproductive cycles. More broadly, our data indicate that physiological experience can broadly alter epigenetic states, functionally modifying the capacity of the affected cells to respond to later stimulatory events. Mammary gland cells (six distinct cell types) from nulliparous and parous female mice were FACS-sorted using a combination of cell surface markers. Genomic DNA was bisulfite converted and used to obtain genome-wide DNA methylation profiles. The current work focuses on the analysis of the first 12 samples (GSM1646785-96) and uses the other two samples to confirm some properties of the analysis results based on samples 1-12. Consequently, samples GSM1646797, GSM1646798 were analyzed in a much more limited manner compared to the other 12 samples, generating two plots included in the associated manucript.

2015-05-15 | E-GEOD-67386 | biostudies-arrayexpress

Expression data from mammary gland during pregnancy and lactation of CBA/CaH, QSi5 and Advanced Intercross Line (AIL; CBA/CaH X QSi5, the 14th generation)

Project description:Previously we have shown significant differences in lactation performance, mammary gland histology and expression profiles of mammary transcriptome during peak-lactation (lactation day 9; L9) between the ordinary CBA/CaH (CBA) and the superior QSi5 strains of mice. In the present study, we compared mammary gland histology between CBA and QSi5 at mid-pregnancy (pregnancy day 12; P12). We assessed lactation performance during the first 8 days of lactation of the 13th - 14th generation of the Advanced Intercross Line (AIL) (CBA X QSi5) mice. We utilized an integrative approach to analyzing mammary microarray expression profiles of CBA and QSi5 at P12 and CBA, AIL and QSi5 at L9. The inguinal mammary glands of CBA/CaH and QSi5 during mid-pregnancy (Pregnancy day 12; P12), and the glands of CBA/CaH, AIL and QSi5 during peak lactation (Lactation day 9; L9) were collected and total RNA was extracted for Affymetrix microarray (mouse genome 430 2) assay

2013-01-22 | E-GEOD-32020 | biostudies-arrayexpress

Pregnancy-associated alterations in DNA methylation patterns of mammary epithelial stem cells [inhibitor study]

Project description:Mammary gland development and luminal differentiation occur largely postnatally during puberty and pregnancy. To explore the role of DNA methylation in luminal cell differentiation and pregnancy-induced changes, we determined the genome-wide DNA methylation and gene expression profiles of mammary epithelial stem, luminal progenitor, and mature luminal cells at different reproductive stages. We found that pregnancy had the most significant effects on stem cells, inducing a distinct epigenetic state that remained stable through life. Integrated analysis of gene expression, DNA methylation, and histone modification profiles revealed cell type and reproductive stage-specific changes in molecular signatures. We also identified p27 and TGFβ signaling as key regulators of luminal progenitor cell proliferation based on their expression patterns and by the use of explant cultures. Our results suggest relatively minor changes in DNA methylation during luminal cell differentiation as compared to the significant effects of pregnancy on mammary epithelial stem cells. Mammary glands were collected from mice treated with DNA methylation inhibitor 5-azacytidine (AzaC) and histone deacetylase inhibitor valproic acid (VPA) at non-pregnant and pregnant stages for RNA extraction and hybridization on Affymetrix microarrays.

2015-01-22 | E-GEOD-54148 | biostudies-arrayexpress

Pregnancy-associated alterations in DNA methylation patterns of mammary epithelial stem cells [inhibitor study]

2015-01-22 | GSE54148 | GEO

Expression data from mammary gland during pregnancy and lactation of CBA/CaH, QSi5 and Advanced Intercross Line (AIL; CBA/CaH X QSi5, the 14th generation)

2013-01-22 | GSE32020 | GEO

Prenatal exposure to bisphenol A, genistein and indole-3-carbinol on early mammary gland development and carcinogenesis in female Sprague-Dawley offspring

Project description:Rodent studies have indicated that gestational and perinatal bisphenol A (BPA) exposure increase the risk of developing breast cancer during adulthood. In contrast, some dietary compounds such as genistein (GEN) and indole 3-carbinol (I3C) present potential protective effects against inducing hormone-dependent cancers, including that of the mammary gland. Thus, we aimed to evaluate the role of these dietary compounds on early mammary gland development and carcinogenesis in female Sprague-Dawley offspring. Pregnant Sprague-Dawley (SD) rats were treated with BPA at 25 or 250µg/kg b.w./day by gavage from gestational day (GD) 10 to 21 with or without dietary GEN (250 mg/kg chow, ~5.5 mg/kg b.w./day) or I3C (2000 mg/kg chow, ~45.0 mg/kg b.w./day). At post-natal day (PND) 21, some female offspring from different litters were euthanized for mammary gland development and gene expression analyses while other female offspring received a single dose of N-methyl-N-nitrosourea (MNU) for mammary carcinogenesis initiation. The findings this study indicated the prenatal exposure to BPA, GEN and I3C did not significantly alter ductal elongation, number of terminal end buds (TEB) or cell proliferation, and estrogen receptor alpha (ER-α) immunostaining expression in epithelial mammary cells at PND 21. BPA treatment modulated the expression of several genes, but these changes were not associated with a dose dependent response. Dietary GEN and I3C treatment causally and consistent with the mammary gland structures outcomes. Besides, maternal BPA exposure associated with dietary GEN and I3C did not alter the susceptibility to the mammary cancer development in adulthood when the carcinogen was administered in a window of immature mammary gland development.

2016-06-03 | GSE68973 | GEO

Mammary gland development: cross-species analysis of the mammary gland transcriptome in pregnant or lactating wild type female Sprague Dawley rats.

Project description:Cross-species hybridization analysis of mammary glands during pregnancy and lactation. Results provide insight into putative conserved molecular mechanisms regulating mammary gland development. This study was performed to identify orthologous transcripts that are differentially co-expressed in the mammary gland at 2 stages of development (pregnancy and lactation) in wild type Sprague-Dawley rats.

2013-10-30 | GSE22545 | GEO

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