Cited research: J. Cell Biol. doi:10.1083/jcb.200909113 (2010)

In order to spread, or metastasize, tumour cells must break through the basement membrane that separates the tumour from the underlying tissue. Using in vitro assays to mimic this invasion, Marie Schoumacher and Danijela Vignjevic of the Curie Institute in Paris and their co-workers surmised that the process occurs in stages. First, finger-like protrusions called invadopodia form at the tumour-cell surface and punch a hole through the basement membrane. These then elongate before leading the cells into the tissue beneath.

The team used molecular markers and selective gene silencing to identify three classes of protein filaments that drive this process. Actin filaments, which are known to help other cells migrate, are vital for the first stage. As the invadopodia elongate, other protein filaments — microtubules and vimentin intermediate filaments — help the actin network to further lengthen the protrusions.