Invadopodia protrude into the matrix in CIA.

(A) MDA-MB-231 cells completely embedded in collagen I also show similar elongated morphology as in CIA. Staining of N-WASP or cortactin (green) and actin (red) show that N-WASP and filamentous actin containing structures resembling invadopodia (white arrowheads) are also present in cells migrating in a pure 3D environment. Scale bar 20 µm. (B) Z-stack projection showing invadopodia-like structures (arrowheads) localize to various positions, including the front of the invading pseudopods facing upward into the Matrigel and at the periphery and dorsal surface. Staining shows N-WASP (green), actin (red) and DAPI (blue) or cortactin (blue). See also Movie S8.