At the cellular level, Garros-Regulez et al. [33] proposed SOX2 upregulation via activation of GBM-specific signaling pathways that maintain the overexpression of SOX2 via transforming growth factor-beta (TGF-β), Sonic Hedgehog (SHH), epidermal growth factor receptor (EGFR), and fibroblast growth factor receptor (FGFR) pathways. Here, SHH is linked to glioblastoma.