Neovascularization plays a substantial role in the regulation of invasion of glioblastoma. However, the underlying molecular basis remains largely unknown. Both vascular endothelial growth factor a (VEGFa) and matrix metalloproteinases 2 (MMP2) are essential for cancer neovascularization and cancer invasion in that they promote endothelial mitogenesis and permeability, and promote extracellular matrix degradation, respectively. In the current study, we found strong positive correlation of VEGFa and phosphorylated MMP2 levels in the glioblastoma from the patients. Thus, we used a human glioblastoma line, A-172, to examine the interaction of VEGFa and MMP2. We found that overexpression of VEGFa in A-172 cells increased MMP2 levels, while inhibition of VEGFa in A-172 cells decreased MMP2 levels. On the other hand, forced changes in MMP2 levels in A-172 cells did not affect VEGFa levels. These data suggest that VEGFa may regulate MMP2 in glioblastoma, while MMP2 did not appear to affect VEGFa levels. We then examined the signaling pathways involved in the regulation of MMP2 levels by VEGFa. Application of a specific extracellular-related kinase 1/2 (ERK1/2) inhibitor, but not application of either an protein kinase B (Akt) inhibitor, or a Jun N-terminal kinase (JNK) inhibitor to VEGFa-overexpressing A-172 cells substantially abolished the effect of VEGFa on MMP2 activation, suggesting that VEGFa may increase MMP2 levels via ERK/mitogen-activated protein kinase (MAPK), but not phosphatidylinositol 3-kinase (PI3K) or JNK signaling pathways in glioblastoma. Moreover, adapted VEGFa levels were found to directly and positively affect the glioblastoma development in an intracranial glioblastoma implantation model. Taken together, our data suggest that anti-VEGFa treatment in glioblastoma may inhibit neovascularization not only by VEGFa itself but also by its regulatory effect on MMP2.
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