Co-localization of cortactin and phosphotyrosine identifies active invadopodia in human breast cancer cells.
ABSTRACT Invadopodia are filopodia-like projections possessing protease activity that participate in tumor cell invasion. We demonstrate that co-localization of cortactin and phosphotyrosine identifies a subset of cortactin puncta termed "invadopodial complexes" that we find to be closely associated with the plasma membrane at active sites of focal degradation of the extracellular matrix in MDA-MB-231 breast cancer cells. Manipulation of c-Src activity in cells by transfection with kinase activated c-Src(527) or kinase inactive c-Src(295) results in a dramatic increase or decrease, respectively, in the number of these structures associated with changes in the number of sites of active matrix degradation. Overexpression of kinase-inactive c-Src(295) does not prevent localization of cortactin at the membrane; however, co-localized phosphotyrosine staining is decreased. Thus, elevated phosphotyrosine at invadopodial complexes is specifically associated with the proteolytic activity of invadopodia. Further, invadopodial complexes are spatially, morphologically and compositionally distinct from focal adhesions as determined by localization of focal adhesion kinase (FAK), which is not present in invadopodial complexes. Expression of kinase-inactive c-Src(295) blocks invadopodia activity, but does not block filopodia formation. Thus, invadopodia, but not filopodia, are highly correlated with matrix invasion, and sites of invadopodial activity can be identified by the formation of invadopodial complexes.
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ABSTRACT: The leading cause of death in cancer patients is metastasis. Invasion is an integral part of metastasis and is carried out by proteolytic structures called invadopodia at the cellular level. In this introductory review, we start by evaluating the definition of invadopodia. While presenting the upstream signaling events involved, we integrate current models on invadopodia. In addition, we discuss the significance of invadopodia in 2D and 3D and in vivo. We finally point out technical challenges and conclude with open questions in the field.Turkish Journal of Biology 11/2014; 38(6):740-747. · 1.22 Impact Factor
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ABSTRACT: Tks5 (tyrosine kinase substrate with 5 SH3 domains) is an adaptor protein which cooperates with Src tyrosine kinase to promote the formation of protease-enriched, actin-based projections known as invadopodia, which are utilized by invasive cancer cells to degrade the extracellular matrix (ECM). We previously identified a Src-Tks5-Nck pathway which promotes invadopodium formation and ECM proteolysis in melanoma and breast cancer cells. We therefore sought to investigate the significance of Tks5 expression in human cancers. This was undertaken retrospectively through an immunohistochemical evaluation in tissue microarray cores and through data mining of the public database, Oncomine. Here we showed that Tks5 was expressed at higher levels in the microarray cores of breast, colon, lung and prostate cancer tissues compared to the levels in normal tissues. Importantly, mining of Oncomine datasets revealed a strong correlation between Tks5 mRNA overexpression in a number of cancers with increased metastatic events and a poorer prognosis. Collectively, these findings suggest a clinical association of Tks5 expression in human cancers. It identifies the importance for further investigations in examining the full potential of Tks5 as a relevant prognostic marker in a select number of cancers which may have implications for future targeted therapies.Oncology reports. 07/2014;
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ABSTRACT: Melanoma is one of the most deadly cancers because of its high propensity to metastasis, a process that requires migration and invasion of tumor cells driven by the regulated formation of adhesives structures like focal adhesions (FAs) and invasive structures like invadopodia. FAK, the major kinase of FAs, has been implicated in many cellular processes, including migration and invasion. In this study, we investigated the role of FAK in the regulation of invasion. We report that suppression of FAK in B16F10 melanoma cells led to increased invadopodia formation and invasion through Matrigel, but impaired migration. These effects are rescued by FAK WT but not by FAK(Y397F) reexpression. Invadopodia formation requires local Src activation downstream of FAK and in a FAK phosphorylation-dependant manner. FAK deletion correlates with increased phosphorylation of Tks-5 (tyrosine kinase substrate with five SH3 domain) and reactive oxygen species production. In conclusion, our data show that FAK is able to mediate opposite effects on cell migration and invasion. Accordingly, beneficial effects of FAK inhibition are context dependent and may depend on the cell response to environmental cues and/or on the primary or secondary changes that melanoma experienced through the invasion cycle.Cell Death & Disease 08/2014; 5:e1379. · 5.18 Impact Factor