Project description:Global proteomic profiling of three mammary epithelial cell types in normal human breast tissue. Primary breast specimens were obtained from 10 women undergoing reduction mammoplasties. Clinical co-variates include age (28-67), hormone status (follicular, luteal, post-menopausal) and mammary epithelial cell type (basal, luminal progenitor, mature luminal).
Project description:Mammary gland homeostasis is maintained by adult tissue stem-progenitor cells residing within the luminal and basal epithelia. Dysregulation of mammary stem cells is a key mechanism for cancer development. However, stem cell characterization is challenging because reporter models using cell-specific promoters do not fully recapitulate the mammary stem cell populations. We previously found that a 270-basepair Runx1 enhancer element, named eR1, marked stem cells in the blood and stomach. Here, we identified eR1 activity in a rare subpopulation of the ERα-negative luminal epithelium in mouse mammary glands. Lineage-tracing using an eR1-CreERT2 mouse model revealed that eR1+ luminal cells generated the entire luminal lineage and milk-secreting alveoli – eR1 therefore specifically marks lineage-restricted luminal stem cells. eR1-targeted-conditional knockout of Runx1 led to the expansion of luminal epithelial cells, accompanied by elevated ERα expression. Our findings demonstrate a definitive role for Runx1 in the regulation of the eR1-positive luminal stem cell proliferation during mammary homeostasis. Our findings identify a mechanistic link for Runx1 in stem cell proliferation and its dysregulation in breast cancer. Runx1 inactivation is therefore likely to be an early hit in the cell-of-origin of ERα+ luminal type breast cancer.
Project description:Insulin like growth factor binding protein 7, Igfbp7, is a secreted protein that in addition to modulating insulin and insulin-like growth factor signaling, it acts as a tumor suppressor gene in breast and other cancers. To elucidate the role of Igfbp7 in regulating the proliferation and differentiation of mammary epithelial cells, we examined the growth and differentiation of mammary gland through different stages of its development in Igfbp7-null mice. Using transcriptome profiling in addition to functional assays we demonstrate that loss of Igfbp7 leads to diminished luminal cell differentiation and expansion of the luminal progenitors. These studies identify the endocrine factor Igfbp7, as a key regulator of luminal progenitor functions in the mammary gland. Mammary gland mRNA profiles of lactation day 3 wild type (WT) and Igfbp7-/- (KO) mice were generated by deep sequencing using SOLiD5500xl
Project description:RUNX1 encodes a RUNX family transcription factor (TF) and was recently identified as a novel mutated gene in human luminal breast cancers. We found that Runx1 is expressed in all subpopulations of murine mammary epithelial cells (MECs) except the secretory alveolar luminal cells. Conditional knockout of Runx1 in MECs by MMTV-Cre led to a decrease in luminal MECs, largely due to a profound reduction in the estrogen receptor (ER)-positive mature luminal subpopulation, a phenotype that could be rescued by loss of either Trp53 or Rb1. Mechanistically RUNX1 represses Elf5, a master regulatory TF gene for alveolar cells, and activates Foxa1, a key mature luminal TF gene involved in the ER program. Collectively, our data identified a key regulator of the ER+ luminal lineage whose disruption may contribute to development of ER+ luminal breast cancer when under the background of either TP53 or RB1 loss. Thoracic and inguinal mammary glands from 3 MMTV-Cre;Runx1L/L;R26Y and 3 MMTV-Cre;Runx1+/+;R26Y adult virgin females were dissected out, minced and digested to single cell suspension. Runx1L is the floxed conditional knockout allele of Runx1. R26Y is a conditional YFP reporter that would be turned on upon Cre-mediated recombination. FACSaria machine was used to sort out the YFP-marked luminal epithelial cell population of each of these 6 mice. Total RNA was isolated with Qiagen RNeasy kit and subsequently amplified by Nugen V2 and applied to Affymetrix mouse genome 430 2.0 arrays.
Project description:This experiment shows RNA-Seq gene expression profiles of Wild Type and Slug/Snai2-null luminal, basal, and stromal mammary cell populations from young (3 mo) and aged (12 mo) mice.
Project description:Stat1-null mice (129S6/SvEvTac-Stat1tm1Rds homozygous) uniquely develop estrogen-receptor-positive mammary tumors with incomplete penetrance and long latency. We studied the growth and development of the mammary glands in Stat1-null mice. Stat1-null MGs have faulty branching morphogenesis with abnormal terminal end buds. The Stat1-null MG also fails to sustain growth of 129S6/SvEv wild-type and null epithelium. These abnormalities are partially reversed by added progesterone and prolactin. Transplantation of wild-type bone-marrow into Stat1-null mice does not reverse the mammary gland developmental defects. Media conditioned by Stat1-null epithelium-cleared mammary fat pads does not stimulate epithelial proliferation whereas it is stimulated by conditioned media derived from either wild-type or progesterone and prolactin-treated Stat1-null epithelium-cleared mammary fat pads. Microarrays and multiplex cytokine protein assays showed that the mammary gland of Stat1-null mice had lower levels of growth factors that have been implicated in normal mammary gland growth and development. Transplanted Stat1-null tumors and their isolated cells also grow slower in Stat1-null mammary gland compared to wild-type recipient mammary gland. Stat1-null hosts responded to tumor transplants with granulocytic infiltrates while wild-type hosts show a mononuclear response. These studies demonstrate that growth of normal and neoplastic Stat1-null epithelium primarily depends on the hormonal milieu and factors, such as cytokines, from the mammary stroma.
Project description:Mammary stem and progenitor cells are essential for mammary gland homeostasis and are also candidates for cells of origin of mammary tumors. Here, we provide evidence that the protein kinase p38a is required for the differentiation of luminal progenitor cells through modulation of the transcription factors Runx1 and Foxa1. Moreover, using a mouse model for breast cancer initiated by luminal cells, we show that p38a downregulation in mammary epithelial cells reduces tumorigenesis, which correlates with reduced numbers of tumor-initiating cells. Our results identify p38a as a key regulator of luminal progenitor cell fate that facilitates mammary tumor formation.
Project description:RUNX1 encodes a RUNX family transcription factor (TF) and was recently identified as a novel mutated gene in human luminal breast cancers. We found that Runx1 is expressed in all subpopulations of murine mammary epithelial cells (MECs) except the secretory alveolar luminal cells. Conditional knockout of Runx1 in MECs by MMTV-Cre led to a decrease in luminal MECs, largely due to a profound reduction in the estrogen receptor (ER)-positive mature luminal subpopulation, a phenotype that could be rescued by loss of either Trp53 or Rb1. Mechanistically RUNX1 represses Elf5, a master regulatory TF gene for alveolar cells, and activates Foxa1, a key mature luminal TF gene involved in the ER program. Collectively, our data identified a key regulator of the ER+ luminal lineage whose disruption may contribute to development of ER+ luminal breast cancer when under the background of either TP53 or RB1 loss.
Project description:Insulin like growth factor binding protein 7, Igfbp7, is a secreted protein that in addition to modulating insulin and insulin-like growth factor signaling, it acts as a tumor suppressor gene in breast and other cancers. To elucidate the role of Igfbp7 in regulating the proliferation and differentiation of mammary epithelial cells, we examined the growth and differentiation of mammary gland through different stages of its development in Igfbp7-null mice. Using transcriptome profiling in addition to functional assays we demonstrate that loss of Igfbp7 leads to diminished luminal cell differentiation and expansion of the luminal progenitors. These studies identify the endocrine factor Igfbp7, as a key regulator of luminal progenitor functions in the mammary gland.