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.
Project description:The mouse mammary gland undergoes severe morphological changes during each pregnancy cycle. These are controlled by epithelial as well as stromal factors, including fibroblasts. This project aimed to identify factors that are expressed in mammary fibroblasts during early pregnancy (day3) when the first morphological changes become microscopically visible.
Project description:Here, we show that functional loss of a single gene is sufficient to confer constitutive milk protein production and protection against mammary tumor formation. Caveolin-3 (Cav-3), a muscle-specific caveolin-related gene, is highly expressed in striated and smooth muscle cells. We demonstrate that Cav-3 is also expressed in myoepithelial cells within the mammary gland. To determine if genetic ablation of Cav-3 expression affects adult mammary gland development, we next studied the phenotype(s) of Cav-3 (-/-) null mice. Interestingly, detailed analysis of Cav-3 (-/-) virgin mammary glands shows dramatic increases in ductal thickness, side-branching, and the development of extensive lobulo-alveolar hyperplasia, akin to the changes normally observed during pregnancy and lactation. Analysis by genome-wide expression profiling reveals the upregulation of gene transcripts associated with pregnancy/lactation, mammary stem cells, and human breast cancers, consistent with a constitutive lactogenic phenotype. The expression levels of three key transcriptional regulators of lactation, namely Elf5, Stat5a, and c-Myc are also significantly elevated. Experiments with pregnant mice directly show that Cav-3 (-/-) mice undergo precocious lactation. Finally, using orthotopic implantation of a transformed mammary cell line (known as Met-1), we demonstrate that virgin Cav-3 (-/-) mice are dramatically protected against mammary tumor formation. Interestingly, Cav-3 (+/-) mice also show similar protection, indicating that even reductions in Cav-3 levels are sufficient to render these mice resistant to tumorigenesis. Thus, Cav-3 (-/-) mice are a novel preclinical model to study the protective effects of a constitutive lactogenic microenviroment on mammary tumor onset and progression. Our current studies have broad implications for using the lactogenic micro-environment as a paradigm to discover new therapies for the prevention and/or treatment of human breast cancers. Most importantly, a lactation-based therapeutic strategy would provide a more natural and nontoxic approach to the development of novel anti-cancer therapies. Experiment Overall Design: All WT and Cav-3 knockout (KO) mice used in this study were in the FVB/N genetic background. 4-month old virgin female mice were utilized in a micro array study between 3 wildtype and 3 Caveolin-3 knock-out mammary glands.
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.
Project description:Here, we show that functional loss of a single gene is sufficient to confer constitutive milk protein production and protection against mammary tumor formation. Caveolin-3 (Cav-3), a muscle-specific caveolin-related gene, is highly expressed in striated and smooth muscle cells. We demonstrate that Cav-3 is also expressed in myoepithelial cells within the mammary gland. To determine if genetic ablation of Cav-3 expression affects adult mammary gland development, we next studied the phenotype(s) of Cav-3 (-/-) null mice. Interestingly, detailed analysis of Cav-3 (-/-) virgin mammary glands shows dramatic increases in ductal thickness, side-branching, and the development of extensive lobulo-alveolar hyperplasia, akin to the changes normally observed during pregnancy and lactation. Analysis by genome-wide expression profiling reveals the upregulation of gene transcripts associated with pregnancy/lactation, mammary stem cells, and human breast cancers, consistent with a constitutive lactogenic phenotype. The expression levels of three key transcriptional regulators of lactation, namely Elf5, Stat5a, and c-Myc are also significantly elevated. Experiments with pregnant mice directly show that Cav-3 (-/-) mice undergo precocious lactation. Finally, using orthotopic implantation of a transformed mammary cell line (known as Met-1), we demonstrate that virgin Cav-3 (-/-) mice are dramatically protected against mammary tumor formation. Interestingly, Cav-3 (+/-) mice also show similar protection, indicating that even reductions in Cav-3 levels are sufficient to render these mice resistant to tumorigenesis. Thus, Cav-3 (-/-) mice are a novel preclinical model to study the protective effects of a constitutive lactogenic microenviroment on mammary tumor onset and progression. Our current studies have broad implications for using the lactogenic micro-environment as a paradigm to discover new therapies for the prevention and/or treatment of human breast cancers. Most importantly, a lactation-based therapeutic strategy would provide a more natural and nontoxic approach to the development of novel anti-cancer therapies.
Project description:Changes in mammary cell behavior mediating normal breast development during pregnancy and lactation are poorly understood due to limited availability of breast biopsies during this time. Human milk contains a hierarchy of cells including stem cells, mature milk producing cells (lactocytes) and myoepithelial cells. Here we non-invasively sampled the total epithelial cell population of the lactating mammary gland from mature HM collected from healthy mother/infant dyads during the first year postpartum, and explored temporal changes in the mammary cell transcriptome using RNA sequencing. Comparisons were done with mammary secretions from late pregnancy from the same women and with purchased resting mammary tissue. Distinct gene signatures were found for the different mammary developmental stages examined. Cell adhesion pathways were differentially regulated between the resting gland and pregnancy, whereas immune cell signaling and morphogenesis/cancer pathways differed between lactation and pregnancy or the resting gland, respectively. The transcriptome of lactation remained consistent in the first year postpartum in these successfully lactating women. The gene signatures characteristic of HM cells confirmed lactation genes previously reported in animal models and the HM fat globule. This study identifies key genes and molecular pathways undergoing controlled regulation as the mammary gland transitions from a quiescent into a functional organ, providing experimental targets for the molecular investigation of mammary gland pathologies.
Project description:Mammary gland development: cross-species analysis of the mammary gland transcriptome in pregnant or lactating wild type female Sprague Dawley rats.
Project description:Early full-term pregnancy affords lifetime protection against development of breast cancer. Parity-induced protection can be reproduced in a carcinogen-induced rat mammary carcinoma model. The molecular mechanisms of parity-induced protection against carcinogenic stimuli in rat mammary glands have not been fully characterized. In order to gain a better understanding of these molecular mechanisms, we performed gene expression analyses in parous and age-matched virgin (AMV) mammary glands of Lewis rats before and after carcinogen (N-methyl-N-nitrosourea; MNU) treatment.