In addition to NOX4, we used antibodies against Nestin and SOX2, which are established stem‐cell markers in GBM, and GFAP as an indicator of the astrocytic lineage in TMA1 (Fig. 1D, left); in the second TMA (Fig. 1D, right, Fig. 1E, Fig. S2) we added CD44 antibody to better identify stem cells. Here, NOX4 is linked to glioblastoma.