(a) Primary siRNA screening analysis. MDA-MB-231 cells reverse transfected with siRNA pools against MT1-MMP, TKS5, or each human RAB GTPase were plated on fluorescein-labeled-gelatin coated optical microplates. Degradation activity was measured by counting the number of cells degrading gelatin identified as dark black foci (similar results were obtained by measuring the area of degradation/number of cells). The inset shows representative images of degraded Oregon green gelatin (upper panels) and merged images with TRITC-phalloidin (red) and DAPI (blue) in scrambled siRNA (NC), or siRNA against RAB28 or RAB42 transfected cells (lower panel). Data are means ± SEM of 3 independent experiments. Bar, 50 µm. 