Abstract
Transforming growth factor-β (TGFβ) is a potent regulator of tumorigenesis, although mechanisms defining its tumor suppressing and tumor promoting activities are not understood. Here we describe phosphoproteome profiling of TGFβ signaling in mammary epithelial cells, and show that 60 identified TGFβ-regulated phosphoproteins form a network with scale-free characteristics. The network highlighted interactions, which may distribute signaling inputs to regulation of cell proliferation, metabolism, differentiation and cell organization. In this report, we identified two novel and TGFβ-dependent phosphorylation sites of 14-3-3σ, i.e. Ser69 and Ser74. We observed that 14-3-3σ phosphorylation is a feed-forward mechanism in TGFβ/Smad3-dependent transcription. TGFβ-dependent 14-3-3σ phosphorylation may provide a scaffold for the formation of the protein complexes which include Smad3 and p53 at the Smad3-specific CAGA element. Furthermore, breast tumor xenograft studies in mice and radiobiological assays showed that phosphorylation of 14-3-3σ at Ser69 and Ser74 is involved in regulation of cancer progenitor population and radioresistance in breast cancer MCF7 cells. Our data suggest that TGFβ-dependent phosphorylation of 14-3-3σ orchestrates a functional interaction of TGFβ/Smad3 with p53, plays a role in the maintenance of cancer stem cells and could provide a new potential target for intervention in breast cancer.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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14-3-3 Proteins / metabolism*
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Animals
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Biomarkers, Tumor / metabolism*
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Breast Neoplasms / genetics
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Breast Neoplasms / metabolism
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Cell Line
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Exonucleases / metabolism*
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Exoribonucleases
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Female
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Gene Expression Regulation* / drug effects
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Heterografts
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Humans
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MCF-7 Cells
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Mice
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Models, Biological
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Neoplastic Stem Cells / drug effects
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Neoplastic Stem Cells / metabolism
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Phosphoproteins / metabolism
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Phosphorylation / drug effects
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Protein Binding
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Protein Interaction Maps
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Proteome
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Radiation Tolerance*
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Signal Transduction / drug effects
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Smad3 Protein / metabolism
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Transcription, Genetic*
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Transcriptional Activation
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Transforming Growth Factor beta1 / metabolism*
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Transforming Growth Factor beta1 / pharmacology
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Tumor Suppressor Protein p53 / metabolism
Substances
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14-3-3 Proteins
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Biomarkers, Tumor
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Phosphoproteins
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Proteome
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Smad3 Protein
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Transforming Growth Factor beta1
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Tumor Suppressor Protein p53
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Exonucleases
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Exoribonucleases
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SFN protein, human
Grants and funding
Works in Souchelnytskyi group are supported by Karolinska Biomics Center, Dep. of Oncology-Pathology, Karolinska Institute, Radiumhemmet Research Funds, Karolinska University Hospital, the Swedish Cancer Society (CF), the Swedish Research Council (VR), INTAS, FEBS, EU RTN EpiPlast Carcinoma, Eurocan Platform and UICC. Works in Dubrovska group are supported by the German Federal Ministry of Education and Research (Grant-No. 03Z1NN11). This study was supported in part by Susan G. Komen for the Cure Grant PDF0707903 (to A.D). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.