Most cancer related deaths are due to the spread of a primary tumour and the formation of secondary metastases. Invasion of malignant cells through tissues is a fundamental step in the metastatic cascade that is reliant on the degradation of the extracellular matrix (ECM). Several invasive neoplasms, including melanoma and breast carcinoma, possess dynamic actin-based membrane protrusions called invadopodia that release extracellular proteases which degrade the ECM. Invadopodia formation is initiated by adhesion of malignant cells to the ECM and activation of proteins and lipids involved in signal transduction, cytoskeletal remodelling, vesicular trafficking and ECM proteolysis. Central to invadopodia formation is the SRC tyrosine kinase. Knockdown or inhibition of SRC or several downstream substrates that SRC phosphorylates blocks invadopodia formation, while overexpression of SRC strongly enhances invadopodia formation. The perceived importance of SRC in cancer, particularly cancer invasion, is reflected by the fact that many SRC inhibitors are now in clinical development as cancer therapies. We hypothesized that unknown SRC targets could be present in invadopodia and that targeting of these molecules could provide a valuable strategy to block cancer invasion. Using a proteomic screen to identify SRC substrates and confocal microscopy and RNA interference to identify proteins that localise to and are required for invadopodia formation, we have identified several candidate molecules of interest. One of these, Inv1 is an adaptor protein involved in actin cytoskeletal dynamics and has further been shown to be up-regulated in the metastases of a range of malignancies. Remarkably, despite being identified on the basis of its elevated tyrosine phosphorylation almost 20 years ago, the significance and location of Inv1 tyrosine phosphorylation sites remained unknown. We now show that Inv1 is phosphorylated on six tyrosine residues upon SRC activation. Our studies are addressing the functional requirement for these tyrosine phosphorylation sites in invadopodia regulation.