Figure 3.

Protease activity during invasion of MDA-MB-231 cells into 30-μm-thick Matrigel networks. Cells were transfected with the MT1-MMP FRET biosensor to detect the activity of MT1-MMP at the cell surface. High FRET ratio indicates active MTI-MMPs at the cell surface. (A) MT1-MMP activity map for cells invading 30-μm -thick Matrigel for low (ϕ_3D < 10°) and high (ϕ_3D > 20°) angles of 3D indentation. The MMP inhibitor GM6001 was used as a control (left). (B) The mean FRET ratios for the cells shown in A. These ratios were found to be significantly lower for cells at low ϕ_3D than for those at high ϕ_3D. ^∗∗p < 0.05, calculated using Student’s t-test (n > 12). (C) Fluorogenic peptide assay for broad-spectrum secreted proteases measured at 405 nm wavelength is shown for negative controls (NC), 231, and positive controls (PC). Negative controls indicate growth medium collected from acellular Matrigel, and positive controls indicate growth medium collected from acellular Matrigel containing bovine collagenase IV, whereas 231 indicates medium collected from Matrigel networks with invading MDA-MB-231 cells (ϕ_3D > 20°). ^∗∗p < 0.005, calculated based on one-way analysis of variance followed by the Bonferroni posttest (n = 3). Error bars indicate the mean ± SD. To see this figure in color, go online.