OLIG2 and glioblastoma: The tumor core areas exhibited higher immunoreactivity to hypoxic and mesenchymal GBM markers (HIF1α, YKL-40, p-65 NF-κB and ALDH1A3)30–33 (Figs. 3f and S3b), while the edge regions had higher levels of proneural markers PDGFRA and Olig2 (Fig. S3b).