The metastasis-promoting protein S100A4 regulates mammary branching morphogenesis |
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Authors: | Andersen Kristin Mori Hidetoshi Fata Jimmie Bascom Jamie Oyjord Tove Mælandsmo Gunhild M Bissell Mina |
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Institution: | aLife Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA, USA;bDepartment of Tumor Biology, Institute for Cancer Research, Oslo University Hospital, Radiumhospitalet, Oslo, Norway;cDepartment of Biology, College of Staten Island, City University of New York, NY, USA;dDepartment of Pharmacy, Faculty of Health Sciences, University of Tromsø, Tromsø, 9037 Tromsø, Norway |
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Abstract: | High levels of the S100 calcium binding protein S100A4 also called fibroblast specific protein 1 (FSP1) have been established as an inducer of metastasis and indicator of poor prognosis in breast cancer. The mechanism by which S100A4 leads to increased cancer aggressiveness has yet to be established; moreover, the function of this protein in normal mammary gland biology has not been investigated. To address the role of S100A4 in normal mammary gland, its spatial and temporal expression patterns and possible function in branching morphogenesis were investigated. We show that the protein is expressed mainly in cells of the stromal compartment of adult humans, and during active ductal development, in pregnancy and in involution of mouse mammary gland. In 3D culture models, topical addition of S100A4 induced a significant increase in the TGFα mediated branching phenotype and a concomitant increase in expression of a previously identified branching morphogen, metalloproteinase-3 (MMP-3). These events were found to be dependent on MEK activation. Downregulation of S100A4 using shRNA significantly reduced TGFα induced branching and altered E-cadherin localization. These findings provide evidence that S100A4 is developmentally regulated and that it plays a functional role in mammary gland development, in concert with TGFα by activating MMP-3, and increasing invasion into the fat pad during branching. We suggest that S100A4-mediated effects during branching morphogenesis provide a plausible mechanism for how it may function in breast cancer progression. |
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Keywords: | S100A4 Mammary gland Branching MMP-3 TGFα |
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