EB1 Restricts Breast Cancer Cell Invadopodia Formation and Matrix Proteolysis via FAK

Area of Science:

• Cell Biology
• Cancer Research
• Molecular Biology

Background:

• Plus-end tracking proteins (+TIPs) regulate microtubule dynamics crucial for cancer cell migration.
• The role of +TIPs in cancer cell invasion, particularly through invadopodia, remains understudied.
• Invadopodia are critical for extracellular matrix degradation and cancer metastasis.

Purpose of the Study:

• To investigate the function of End Binding protein 1 (EB1), a key +TIP, in invadopodia-mediated cancer cell invasion.
• To elucidate the molecular mechanisms by which EB1 influences invadopodia activity and extracellular matrix degradation.

Main Methods:

• RNA interference (RNAi) to silence EB1, APC, ACF7, CLASP1/2, and CLIP170 in breast cancer cells.
• Assessment of extracellular matrix degradation by cancer cells.
• Analysis of Focal Adhesion Kinase (FAK) expression and activation.
• Western blotting to detect FAK and Src protein levels and activation states.
• Overexpression of wild-type FAK and FAK mutants to assess rescue effects.

Main Results:

• EB1 silencing significantly increased matrix degradation by breast cancer cells.
• Depletion of EB1 partners APC and ACF7 mimicked the effect of EB1 knockdown on matrix degradation.
• EB1, APC, and ACF7 depletion led to decreased expression and activation of FAK.
• Overexpression of wild-type FAK, but not a Src-non-recruitable mutant, reversed the enhanced degradation caused by EB1 depletion.

Conclusions:

• EB1 acts as a negative regulator of invadopodia formation and function.
• EB1 restricts cancer cell invasion by controlling FAK expression/activation and subsequent spatial regulation of Src activity.
• Targeting EB1 may represent a therapeutic strategy to inhibit breast cancer metastasis.