Fig. 6. Doxycycline abolishes MMP9-wt-enhanced tumor angiogenesis. (A) Gelatinolytic activity in crude tumor extracts (left) and sera (right) from untreated (–Dox) or doxycycline-treated mice (+Dox). Solid and open arrowheads indicate migration of proMMP9 and MMP9 forms, respectively, according to the activity detected in HT-1080 medium (H). (B) MMP9 activity was measured in tumor extracts using DQ-gelatin as substrate. Values represent the mean±s.e.m. obtained in triplicates of two samples per group. The value obtained in untreated samples was considered as 100% (^**P<0.05). (C) Average tumor size at 17 weeks. The difference between–Dox (n=6) and +Dox (n=8) tumors was statistically significant (^**P<0.05). (D) Tumor growth kinetics in the same mice as in C, over a 17-week period. Mean values±s.e.m. are represented. (E) Anti-CD31 staining of sections from tumors in–Dox and +Dox-treated mice. Magnificatiox400. (F) Vascular perimeter estimated as the percentage of CD31-stained area. The value obtained for–Dox samples was considered as 100.