Fra-1/AP-1 induces EMT in mammary epithelial cells by modulating Zeb1/2 and TGFβ expression

Area of Science:

• Oncology
• Molecular Biology
• Cell Biology

Background:

• Epithelial-to-mesenchymal transition (EMT) is crucial for development and cancer progression.
• The AP-1 transcription factor Fra-1 is linked to tumorigenesis and EMT in breast cancer.
• Fra-1 expression inversely correlates with distant-metastasis-free survival in breast cancer patients.

Purpose of the Study:

• To investigate the role and evolutionary conservation of Fra-1 in driving EMT.
• To elucidate the molecular mechanisms by which Fra-1 induces EMT and promotes tumor cell invasion.
• To assess the therapeutic potential of targeting Fra-1-mediated pathways.

Main Methods:

• Ectopic expression of Fra-1 in mouse mammary epithelial cells (EpH4).
• Analysis of epithelial and mesenchymal markers, cell proliferation, motility, and invasiveness.
• Molecular analyses including gene expression, promoter binding assays, and reporter assays.
• Inhibition of TGFβ signaling and silencing of Zeb1/Zeb2.

Main Results:

• Ectopic Fra-1 expression induced a mesenchymal phenotype, increasing proliferation, motility, and invasiveness.
• Fra-1 upregulated Tgfβ1, Zeb1, Zeb2, and Slug, and directly bound to tgfb1, zeb2, and zeb1 regulatory regions.
• Silencing Zeb1 or Zeb2 restored epithelial phenotype and reduced tumorigenesis, while TGFβ inhibition had a moderate effect.

Conclusions:

• Fra-1 drives EMT by altering the expression of key EMT-related transcription factors, conferring invasive and tumorigenic properties.
• Fra-1's function in EMT is evolutionarily conserved between human and mouse cells.
• Fra-1's direct regulation of tgfb1, zeb1, and zeb2 provides a basis for preclinical studies and therapeutic strategies targeting cancer metastasis.