Matrigel penetration does not require MMP-mediated proteolysis. Transwell membranes coated with Matrigel (1.0 μg/mm2) were biotinylated prior to seeding of cells. Membranes were and fixed and stained with FITC-streptavidin at assay termination. Representative areas recorded at 16× magnification are shown. A, Control membrane (no cells applied) reveals the Matrigel pools within and occludes the transwell pores, in a similar manner to the collagen I matrix. B, Confocal microscopy of biotinylated Matrigel-coated transwells indicates HEY and ES-2 cell perforation of Matrigel-plugged transwell pores is unaffected by MMP blockade (GM6001). A magnified view of the transwell pores is provided above. C, Transwell Matrigel penetration was not prevented by MMP inhibition. Cell quantification was performed 55 hrs after seeding. Bars represent the mean ± S.E. *Significantly different from control (p < 0.05; 2-tailed t-test).