FAK balances invadopodia, which promote movement, and focal adhesions that help cells cling to a surface, according to paper in JCB.

The focal adhesion kinase (FAK) coordinates how cancer cells move while at the same time staying attached to a surface, according to a group of investigators. They report that FAK controls movement by balancing the number of invadopodia that create a path for migration and the number of focal adhesions that hold the cell back.

It has been known that FAK spurs focal adhesions to disengage and that it is more abundant in metastatic tumors. Researchers also understood that cancer cells can send out extensions called invadopodia, which release enzymes that dissolve the extracellular matrix (ECM) and clear a path for the cell to move through. As they move, cancer cells gain traction by temporarily attaching to the ECM through focal adhesions.

The current study, published online April 13 in the Journal of Cell Biology, sought to understand whether FAK also regulates invadopodia. The team removed FAK and found that breast cancer cells were much less invasive. To their surprise, however, the FAK-lacking cells sprouted extra invadopodia. The cells also sported large focal adhesions that were particularly sticky.

The group also observed that in FAK-lacking cells, FAK’s helper protein, Src, localized near invadopodia.  Src usually works with FAK to phosphorylate tyrosines in proteins like paxillin, which then disassemble the focal adhesion. Instead, the scientists found that in cells missing FAK, the phosphorylated proteins accumulated in invadopodia. 

The next question, the researchers say, is how FAK and Src integrate these events to promote invasion.

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