Article

Co-localization of cortactin and phosphotyrosine identifies active invadopodia in human breast cancer cells

Department of Oncology, Lombardi Comprehensive Cancer Center, Georgetown University Medical School, Washington, DC 20057-1469, USA.
Experimental Cell Research (Impact Factor: 3.37). 06/2006; 312(8):1240-53. DOI: 10.1016/j.yexcr.2005.12.012
Source: PubMed

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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    • "Invadopodia are relatively dynamic, actin rich, proteolytic cellular structures formed by invasive cancer cells (Bowden et al., 2006; Buccione et al., 2009; Linder, 2009; Linder and Aepfelbacher, 2003) (Figure 2). Invadopodia can be from a few hundred nanometers to several microns wide and can be up to 8 micrometers if the underlying matrix is thick enough (Baldassarre et al., 2003). "
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    • "Maybe that is one of the reasons why SFN inhibited cell migration and invasion in U87MG and U373MG cells. Studies showed that CD44 was related to the pseudopodia formation [45], [46], and CD44 participated in many important cellular processes, including adhesion and motility [47]. CD44v6 is an important member of the cell adhesion molecule CD44 family, and plays a crucial role in tumor invasion [48]. "
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    • "It was thought that actin activity marks the initial stage of invadopodia formation, whereas MMP secretion occurs at the later mature stage of invadopodia activity (Murphy and Courtneidge, 2011). Actin organization in invadopodia can be studied by fluorescence localization of cortactin and F-actin (Bowden et al., 2006; Clark et al., 2007; Eckert et al., 2011; Oser et al., 2009). "
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