A: Western blots from xenograft tissues. Changes in the protein expression of metalloproteinases MMP-9 and MMP-2 and of the transcription factor EGR-1 in xenograft tissues of the six treatment groups. B: Densitometry data of proteins exemplified in Figure 5A. Quantitative densitometry data were generated from triplicate western blots for the determination of MMP-9, MMP-2 and EGR-1in xenograft tissues. The differences among treatment groups were significant (p < 0.001 by Kruskal-Wallis ANOVA). Gemcitabine treatment alone reduced the protein expression of MMP-2 and EGR-1. Simultaneous treatment with nicotine abrogated these responses and additionally increased MMP-9 expression above control levels. GABA showed strong inhibiting effects on all three proteins as a single agent and in combination with gemcitabine. ★Significantly ( p < 0.01 by Mann–Whitney test) different from controls. ✖Significantly (p < 0.01 by Mann–Whitney test) different from gemcitabine alone. Significantly ( < 0.01 by Mann–Whitney test) different from treatment with gemcitabine plus nicotine.