Medium conditioned by heparanase high myeloma cells enhances endothelial invasion via activity of VEGF. (A) Endothelial cells were seeded on the top well of an invasion chamber coated with Matrigel and conditioned medium from either HPSE-low or HPSE-high cells was added to the lower well of the chamber in the presence or absence of a VEGF function blocking antibody. Data are mean ± SD from 3 independent experiments. *P < .001 vs HPSE-low without addition of anti-VEGF. **P < .01 vs HPSE-high. (B) VEGF stimulates ERK activation in endothelial cells. Serum-starved endothelial cells were incubated with conditioned medium from HPSE-high myeloma cells in the presence of VEGF function blocking antibody (Ab-3) or an isotype-matched control antibody. After 15 minutes, whole-cell lysates were prepared and subjected to immunoblotting for p-ERK and t-ERK. (C) VEGF levels are elevated in conditioned medium from HPSE-high cells and a portion of the VEGF associates with syndecan-1. HPSE-low or HPSE-high CAG cells were plated at equal density in complete RPMI medium. After 48 hours, conditioned media were harvested, and the level of VEGF was determined before and after immunodepletion of syndecan-1 (IP SDC1) from the medium (values represent means of triplicate determination ± SD). *P < .001 vs HPSE-low. **P < .001 vs HPSE-high.