MMP inhibition blocks fibroblast-dependent skin cancer invasion, reduces vascularization and alters VEGF-A and PDGF-BB expression.

Tumor invasion requires intense interactions with stromal cells and a profound extracellular matrix remodelling by matrix metalloproteinases (MMPs). Here, we assessed the specific contribution of fibroblasts to tumor invasion, MMPs, tissue inhibitors of MMPs and angiogenesis-related cytokine expression in organotypic cultures of highly malignant HaCaT-ras A-5RT3 cells, with and without MMP inhibition. Collagen degradation, the hallmark of tumor invasion, was dependent on fibroblasts and active MMP-2. Additionally, MMP blockade down-regulated VEGF-A and up-regulated PDGF-BB. These results were paralleled in xenotransplants in vivo, demonstrating strong inhibitory effects of MMP blockade on tumor invasion and vascularization, as shown by the almost complete absence of VEGF-A and MMP-14 and by the decrease in relative blood volume. MMP blockade also increased the fraction of mature vessels, as demonstrated by an increased mean tumor vessel diameter and a higher ratio of Ng2-positive vessels. Thus, this study highlights the importance of targeting the tumor stroma to defeat cancer.