Vascular endothelial growth factor-regulated ovarian cancer invasion and migration involves expression and activation of matrix metalloproteinases

Vascular endothelial growth factor (VEGF) expression is elevated in primary ovarian tumors and metastases. We examined the effect of VEGF on epithelial ovarian cancer (EOC) in vitro invasion and migration and underlying mechanisms. Using the Matrigel invasion assay and colloidal gold phagokinetic track assay, we found that VEGF induced EOC DOV13 invasion and migration in a matrix metalloproteinase (MMP)-dependent manner. Using Western blotting, we show that VEGF, at 20-80 ng/ml, induced secretion of pro-MMP-7 and pro-MMP-9 and activation of pro-MMP-2 in DOV13 conditioned medium in a concentration-dependent manner. However, gelatinolytic activity and total MMP-7 protein in DOV13 conditioned medium reached the maximum upon VEGF treatment at 20-40 ng/ml and decreased at higher-concentration VEGF treatment (80 ng/ml), as shown by DQ-gelatin degradation assay and ELISA. In addition to the effect on MMP secretion/activation, VEGF stimulated secretion of TIMP-2; and blocking TIMP-2 activity by an anti-TIMP-2 MAb significantly increased VEGF (80 ng/ml)-induced DOV13 invasion (p < 0.05), suggesting that VEGF may regulate MMP-2 activity in DOV13 conditioned medium through TIMP-2. Using real-time PCR, we found that VEGF, at 20 ng/ml, significantly increased the expression of VEGFR-1 and VEGFR-2 by approximately 4-fold and 31-fold, respectively, compared to untreated control (p < 0.05). However, the inducing effect of VEGF on VEGFR-2 expression and the internal expression of VEGF121 in DOV13 cells decreased with increasing of VEGF concentration, suggesting the existence of a negative feedback regulatory mechanism. In summary, our results indicate that VEGF may regulate EOC invasion and migration through VEGFR-mediated secretion and activation of MMPs. (c) 2005 Wiley-Liss, Inc.