NCK1 and neoplasm: Along the same line of evidence, the phosphorylation of cortactin on tyrosine 421 is necessary for the release of cofilin from cortactin, and the recruitment of the N-WASp-activator Nck1 to invadopodia, both events relevant for actin polymerization, invadopodia maturation and ultimately tumor cell invasion [42, 44].