Digging a little deeper: The stages of invadopodium formation and maturation

Invadopodia are actin-rich protrusions that degrade the extracellular matrix and are required for penetration through the basement membrane, stromal invasion and intravasation. Invadopodia are enriched in actin regulators, such as cortactin, cofilin, N-WASp, Arp2/3 and fascin. Much of the work to date has centered around identifying the proteins involved in regulating actin polymerization and matrix degradation. Recently, there have been significant advances in characterization of the very early stages of invadopodium precursor assembly and the role of adhesion proteins, such as beta 1 integrin, talin, FAK and Hic-5, in promoting invadopodium maturation. This review summarizes these findings in the context of our current model of invadopodial function and highlights some of the important unanswered questions in the field. (C) 2014 The Authors. Published by Elsevier GmbH.