Importantly, this IL-8-dependent increase in nestin-positive cells directly contributed to the endothelial cell-mediated increase in GBM tumor cell invasion as inhibiting IL-8 in the 3D co-cultures significantly reduced the number of nestin-positive cells that invaded far (>400 μm) into the surrounding collagen matrix (Fig. 5b, bottom). This evidence concerns the gene CXCL8 and glioblastoma.