Multiple domains of cortactin are important for matrix degradation by invadopodia. (A) Western blot of whole-cell lysates from MTLn3 cells transfected with ctrl or cortactin siRNA blotted for cortactin and β-actin. (B) Representative image of cells treated with ctrl or cortactin siRNA and stained for cortactin and F-actin to visualize invadopodium precursors (arrowheads). Bar, 10 μm. (C) Quantification of the percentage of cells that form invadopodium precursors and (D) the degradation area in cells treated with ctrl or cortactin siRNA. (E) Quantification of the number of invadopodium precursors per cell and (F) percentage of cells that form invadopodium precursors in cortactin mutant stable cell lines. P values are compared with WT and graphs show combined data from three independent experiments. (G) Quantification of the Alexa 568-FN degradation area/field normalized to WT cortactin. P values are compared with WT and n = number of fields scored: >80 from more than three independent experiments.