Fig. 3. Transient expression of Snail induces MMP-9 promoter activity and is relieved by siSnail. (A) Activity of the different constructs was analysed in MDCK-CMV cells transiently transfected with Snail cDNA (black bars) or with the empty expression vector (white bars). The effect of Snail is represented for each MMP-9 reporter as fold stimulation of the activity over the empty vector as the mean±s.d. of three independent experiments. (B) The effect of siSnail on MMP-9 promoter activity (construct I) was measured in MDCK-CMV cells growing in T24 plates, after transfection of the indicated amounts of the different vectors and compensated with the empty plasmid. Promoter activity is given as fold stimulation over that with the empty plasmid (mean±s.d. of four independent experiments). (C) Dose-dependent effect of Snail cDNA on the -389 MMP-9 (construct III) promoter activity was analysed in MDCK-CMV cells as described in A. The amount of the Snail cDNA was compensated with empty plasmid up to 1 µg of total DNA. Promoter activity is given as fold stimulation over that obtained in the absence of Snail cDNA. The small panel at the top shows the dose-dependent effect of the empty plasmid on the activity of this promoter construct. Values are the mean±s.d. of three independent experiments.