FOXD1-dependent RalA-ANXA2-Src complex promotes CTC formation in breast cancer

Area of Science:

• Oncology
• Molecular Biology
• Cancer Metastasis Research

Background:

• Early metastasis significantly worsens breast cancer (BC) prognosis.
• Circulating tumor cells (CTCs) are key precursors to metastasis and BC mortality.
• Molecular mechanisms of CTC formation in BC remain incompletely understood.

Purpose of the Study:

• To elucidate the molecular mechanisms driving circulating tumor cell (CTC) formation in breast cancer (BC).
• To investigate the role of FOXD1 in BC metastasis and CTC generation.
• To identify potential therapeutic targets for inhibiting BC metastasis.

Main Methods:

• RNA sequencing of primary BC tissues from patients with high and low CTC counts.
• In vitro and in vivo functional studies using multiple models.
• Mechanistic investigations employing luciferase reporter assays, ChIP-seq, CUT&Tag-seq, and GST-pulldown assays.
• Quantification of CTCs using CanPatrol™ and LiquidBiospy™ systems.
• In vivo treatment with an ERK1/2 inhibitor (SCH772984).

Main Results:

• Highly expressed FOXD1 in primary BC tissues correlates with increased CTCs, especially in early-stage BC.
• FOXD1 overexpression enhances BC cell migration, CTC formation, and metastasis by promoting epithelial-mesenchymal transition.
• FOXD1 directly induces RalA expression, which forms a complex with ANXA2 and Src, increasing ANXA2 phosphorylation and activating the ERK1/2 pathway.
• Inhibition of the RalA-GTP form or ERK1/2 signaling significantly reduces CTC formation and metastasis.

Conclusions:

• A FOXD1-dependent RalA-ANXA2-Src complex activates ERK1/2 signaling, promoting CTC formation and metastasis in breast cancer.
• FOXD1 shows potential as a prognostic factor for evaluating BC metastasis risk.
• The identified signaling cascade is a druggable target for overcoming CTC formation in early-stage BC.