Heparanase promotes endothelial cell invasion and ERK phosphorylation. (A) Cells from myeloma cell lines RPMI 8226 or MM.1S were incubated for 24 hours with rHPSE and the conditioned medium collected. Endothelial cells were then placed in the upper chamber of Matrigel invasion chambers and conditioned medium from myeloma cells placed in the lower chamber. After overnight incubation, endothelial cells that invaded through the Matrigel were fixed, stained, and counted. The control was medium that was not conditioned by cells but with addition of rHPSE. Data are mean ± SD of 3 independent experiments. *P < .01 vs medium from cells not exposed to rHPSE. (B) Medium from myeloma cells was collected 24 hours after addition of rHPSE, added to endothelial cells in culture, and cells extracted and prepared for Western blotting for p-ERK and t-ERK. Bands were scanned and densities shown as ratios of p-ERK to t-ERK.