This analysis identified a number of proteins that have not only been associated with tumor cell invasion/migration in general but also that of GBM cells including osteopontin [38], IL-6 [39], IL-8 [40] MCP-1 [41], VEGF [42], IGFBP-2 [43], GDNF [39], HGF [44], TGFB1 [45] and TGFB2 [39]. Here, GDNF is linked to glioblastoma.