However, it is also likely that tumor cell–microenvironment interactions will have an impact on subtype status and thus tumor aggressiveness in GBM, similar to what has been found for epithelial tumors.35 In this report, we provide evidence for this hypothesis by demonstrating that TGF-β, well known for its ability to induce EMT in epithelial cancers, can induce a ZEB1-dependent mesenchymal transdifferentiation in GBM. This evidence concerns the gene TGFB1 and glioblastoma.