Fig. 3. Tumor invasion is not enhanced by cell surface MMP9 activity. (A) Cell surface-associated MMP9 activity was measured using the fluorogenic substrate M-2055 in intact MCF-7 cells transfected with the MMP9 forms. The fluorescence increment in mock-transfected cells was considered as 1. Data represent mean±s.e.m. of triplicates in one representative experiment of three performed. (B) MMP9-GPI-expressing (a) and MMP9-LDL-expressing (b) MCF-7 cells were incubated with DQ-gelatin and in situ gelatin degradation analyzed by confocal microscopy. Specificity was determined by preincubation of cells with GM6001 (c). Scale bar, 10 µm. (C) Tumor cell intravasation was evaluated by quantitative PCR of human DNA purified from CAM inoculated with MMP9-expressing MCF-7 cells. Data represent the percentage of intravasated human cells in each sample (mock n=21, MMP9-wt n=18, MMP9-GPI n=27 and MMP9-LDL n=22). Mean values for mock transfected, MMP9-wt-, MMP9-GPI- and MMP9-LDL-expressing MCF-7 cells were 0.013, 0.368, 0.057 and 0.016%, respectively (^**P<0.05).