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Updated: Aug 15, 2026

Studying TGF-β Signaling and TGF-β-induced Epithelial-to-mesenchymal Transition in Breast Cancer and Normal Cells
06:54

Studying TGF-β Signaling and TGF-β-induced Epithelial-to-mesenchymal Transition in Breast Cancer and Normal Cells

Published on: October 27, 2020

Breast cancer bone metastasis mediated by the Smad tumor suppressor pathway

Yibin Kang1, Wei He, Shaun Tulley

  • 1Cancer Biology and Genetics Program and Howard Hughes Medical Institute, Molecular Cytology Laboratory, Memorial Sloan-Kettering Cancer Center, NY 10021, USA.

Proceedings of the National Academy of Sciences of the United States of America
|September 21, 2005
PubMed

Insights

Transforming growth factor-beta (TGF-β) signaling switches from tumor suppression to promoting metastasis in breast cancer bone lesions. Smad4 activation drives IL-11 production, contributing to osteolytic bone metastasis.

Area of Science:

  • Molecular Biology
  • Oncology
  • Cancer Metastasis

Background:

  • Transforming growth factor-beta (TGF-β) signaling involves Smad transcription factors, acting as tumor suppressors by inhibiting cell proliferation.
  • Smad-independent TGF-β mechanisms are linked to tumor progression.
  • Breast cancer cells often evade TGF-β's cytostatic effects while maintaining Smad pathway function.

Purpose of the Study:

  • To investigate the role of the Smad pathway in breast cancer bone metastasis.
  • To elucidate the mechanisms by which TGF-β signaling contributes to osteolytic bone lesions.

Main Methods:

  • Immunohistochemical analysis of human breast cancer bone metastases.
  • Functional imaging of the Smad pathway in a mouse xenograft model.
  • Genetic depletion experiments to assess Smad4 function and IL-11 induction.

Main Results:

  • Evidence of active Smad signaling in both human and mouse bone-metastatic lesions.
  • Smad4 depletion inhibited osteolytic bone metastasis formation and IL-11 gene induction.
  • Activator protein-1 (AP-1) was identified as a key factor in Smad-dependent IL-11 transcription and overexpression.

Conclusions:

  • The Smad pathway switches from a tumor-suppressive role to a prometastatic function in breast cancer bone metastasis.
  • Smad4 and IL-11 are critical mediators of osteolytic bone metastasis.
  • Understanding this pathway switch offers potential therapeutic targets for breast cancer bone metastasis.

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