Assay results.

<p>MDA-MB-231 cells transfected with GFP-tagged constitutively active Src exert nearly twice as much total force on the gels via the collagen network as MDA-MB-231s transfected with GFP-tagged wild-type Src (A, p<0.005), while both cell populations travelled at similar speed (F) and with similar migration persistence (G). Compared with the same cell type transfected with GFP-tagged wild-type Src, MDA-MB-231 cells transfected with GFP-tagged constitutively active Src produce extensions that are longer in space (D, p<0.01 E, p<0.00001), and last longer in time (C, p<0.00005) while the number of cells studied was not sufficient to show a difference in overall number of extensions (B). Total stress at each time point was calculated as the sum of the magnitudes of each 3D stress vector calculated on the gel surface, and then averaged over time for the graph. Migration persistence was calculated as total displacement divided by path arclength of the each cell track. Extensions were considered to be cell membrane protrusions that visible in fluorescence that extended for at least 10 µm beyond the presumed cell body, and were measured manually to within the nearest 5 µm. The heavy line is mean, the thinner line median, the box represents the standard deviation, bars represent the full range except for outliers, dots represent outliers. Twenty-one GFP-wt-Src cells and Twenty-four GFP-ca-Src cells were analyzed.