To further validate these findings, we performed western blotting of ten GBM primary cell cultures, which confirmed expression of MDK in GBM cells (Fig. 2b, Supplementary Figs. 3 and 4), as well as western blotting of macrophages and macrophages stimulated with GBM-conditioned media, both with no signs of MDK expression (Supplementary Fig. 4). Here, MDK is linked to glioblastoma.