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Tamoxifen induces pleiotrophic changes in mammary stroma resulting in extracellular matrix that suppresses transformed phenotypes.

ABSTRACT: The functional unit of the mammary gland has been defined as the epithelial cell plus its microenvironment, a hypothesis that predicts changes in epithelial cell function will be accompanied by concurrent changes in mammary stroma. To test this hypothesis, the question was addressed of whether mammary stroma is functionally altered by the anti-oestrogen drug tamoxifen.Forty female rats at 70 days of age were randomised to two groups of 20 and treated with 1.0 mg/kg tamoxifen or vehicle subcutaneously daily for 30 days, followed by a three-day wash out period. Mammary tissue was harvested and effects of tamoxifen on mammary epithelium and stroma determined.As expected, tamoxifen suppressed mammary alveolar development and mammary epithelial cell proliferation. Primary mammary fibroblasts isolated from tamoxifen-treated rats displayed a three-fold decrease in motility and incorporated less fibronectin in their substratum in comparison to control fibroblasts; attributes indicative of fibroblast quiescence. Immunohistochemistry analysis of CD68, a macrophage lysosomal marker, demonstrated a reduction in macrophage infiltration in mammary glands of tamoxifen-treated rats. Proteomic analyses by mass spectrometry identified several extracellular matrix (ECM) proteins with expression levels with tamoxifen treatment that were validated by Western blot. Mammary tissue from tamoxifen-treated rats had decreased fibronectin and increased collagen 1 levels. Further, ECM proteolysis was reduced in tamoxifen-treated rats as detected by reductions in fibronectin, laminin 1, laminin 5 and collagen 1 cleavage fragments. Consistent with suppression in ECM proteolysis with tamoxifen treatment, matrix metalloproteinase-2 levels and activity were decreased. Biochemically extracted mammary ECM from tamoxifen-treated rats suppressed in vitro macrophage motility, which was rescued by the addition of proteolysed collagen or fibronectin. Mammary ECM from tamoxifen-treated rats also suppressed breast tumour cell motility, invasion and haptotaxis, reduced organoid size in 3-dimensional culture and blocked tumour promotion in an orthotopic xenograft model; effects which could be partially reversed by the addition of exogenous fibronectin.These data support the hypothesis that mammary stroma responds to tamoxifen treatment in concert with the epithelium and remodels to a microenvironment inhibitory to tumour cell progression. Reduced fibronectin levels and reduced ECM turnover appear to be hallmarks of the quiescent mammary microenvironment. These data may provide insight into attributes of a mammary microenvironment that facilitate tumour dormancy.

SUBMITTER: Hattar R

PROVIDER: S-EPMC2687708 | biostudies-literature | 2009

REPOSITORIES: biostudies-literature

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Tamoxifen induces pleiotrophic changes in mammary stroma resulting in extracellular matrix that suppresses transformed phenotypes.

Hattar Rhonda R Maller Ori O McDaniel Shauntae S Hansen Kirk C KC Hedman Karla J KJ Lyons Traci R TR Lucia Scott S Wilson R Storey RS Schedin Pepper P

Breast cancer research : BCR 20090127 1

<h4>Introduction</h4>The functional unit of the mammary gland has been defined as the epithelial cell plus its microenvironment, a hypothesis that predicts changes in epithelial cell function will be accompanied by concurrent changes in mammary stroma. To test this hypothesis, the question was addressed of whether mammary stroma is functionally altered by the anti-oestrogen drug tamoxifen.<h4>Methods</h4>Forty female rats at 70 days of age were randomised to two groups of 20 and treated with 1.0 ...[more]

PMID: 19173736

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Project description:BACKGROUND:In utero endocrine disruption is linked to increased risk of breast cancer later in life. Despite numerous studies establishing this linkage, the long-term molecular changes that predispose mammary cells to carcinogenic transformation are unknown. Herein, we investigated how endocrine disrupting compounds (EDCs) drive changes within the stroma that can contribute to breast cancer susceptibility. METHODS:We utilized bisphenol A (BPA) as a model of estrogenic endocrine disruption to analyze the long-term consequences in the stroma. Deregulated genes were identified by RNA-seq transcriptional profiling of adult primary fibroblasts, isolated from female mice exposed to in utero BPA. Collagen staining, collagen imaging techniques, and permeability assays were used to characterize changes to the extracellular matrix. Finally, gland stiffness tests were performed on exposed and control mammary glands. RESULTS:We identified significant transcriptional deregulation of adult fibroblasts exposed to in utero BPA. Deregulated genes were associated with cancer pathways and specifically extracellular matrix composition. Multiple collagen genes were more highly expressed in the BPA-exposed fibroblasts resulting in increased collagen deposition in the adult mammary gland. This transcriptional reprogramming of BPA-exposed fibroblasts generates a less permeable extracellular matrix and a stiffer mammary gland. These phenotypes were only observed in adult 12-week-old, but not 4-week-old, mice. Additionally, diethylstilbestrol, known to increase breast cancer risk in humans, also increases gland stiffness similar to BPA, while bisphenol S does not. CONCLUSIONS:As breast stiffness, extracellular matrix density, and collagen deposition have been directly linked to breast cancer risk, these data mechanistically connect EDC exposures to molecular alterations associated with increased disease susceptibility. These alterations develop over time and thus contribute to cancer risk in adulthood.

Project description:There is limited information on region-specific gene expression in the human corneal stroma. In this study, we aimed to investigate the expression profile of the extracellular matrix and adhesion molecules in the normal corneal stroma using laser capture microdissection (LCM) and molecular techniques.Frozen sections of human cornea without ocular disease were used to isolate the central and peripheral corneal stromal keratocytes by LCM. RNA was extracted from LCM-captured tissues and the RT2 Profiler PCR Arrays were used to examine the expression profile of extracellular matrix and adhesion molecules in the central and peripheral stroma. Real-time quantitative PCR was used to quantify gene expression. Proteomic and western blotting (WB) analyses were performed to confirm gene expression at protein level. Function association network was generated via the web tools String and Cytoscape.The gene expression profiling demonstrated that 35 out of the 84 extracellular matrix and adhesion molecules represented in the array were expressed in stromal keratocytes. Among them, 24 genes were not previously described in the corneal stroma. Two genes were found more abundantly expressed in the central stroma than in the periphery: TGFBI, COL6A2 (p < 0.05). ADAMTS13 was detected only in the central stroma. Proteomics and WB analysis confirmed the expression of 10 genes. Functional analysis revealed that most identified genes were presented in a core cluster that had multiple and strong associations with other genes.This study identified genes not previously described in the corneal stroma, revealed regional differences in gene expression between central and peripheral stroma, and also detected some interesting candidate genes that may play important roles in corneal function. These observations serve as the foundation to further investigate the molecular and cellular mechanisms regulating the pathogenesis of regional corneal stromal disorders such as keratoconus.

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Tamoxifen induces pleiotrophic changes in mammary stroma resulting in extracellular matrix that suppresses transformed phenotypes.

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Tamoxifen induces pleiotrophic changes in mammary stroma resulting in extracellular matrix that suppresses transformed phenotypes.

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