An integrin-linked machinery of cytoskeletal regulation that enables experimental tumor initiation and metastatic colonization.

ABSTRACT

Recently extravasated metastatic cancer cells use the Rif/mDia2 actin-nucleating/polymerizing machinery in order to extend integrin ß1-containing, filopodium-like protrusions (FLPs), which enable them to interact productively with the surrounding extracellular matrix; this process governs the initial proliferation of these cancer cells. Here, we identify the signaling pathway governing FLP lifetime, which involves integrin-linked kinase (ILK) and ß-parvin, two integrinactin-bridging proteins that block cofilin-mediated actin-filament severing. Notably, the combined actions of Rif/mDia2 and ILK/ß-parvin/cofilin pathways on FLPs are required not only for metastatic outgrowth but also for primary tumor formation following experimental implantation. This provides one mechanistic explanation for how the epithelial-mesenchymal transition (EMT) program imparts tumor-initiating powers to carcinoma cells, since it enhances FLP formation through the activation of ILK/ß-parvin/cofilin pathway.