HIF1A and glioblastoma: In brief, the HIF1α signalling pathway, EGFR tyrosine kinase inhibitor resistance pathway and PI3K–AKT signalling pathway regulate GBM progression under hypoxia through the HIF1α/HIF2α–EGF/EGFR–PI3K/AKT–mTOR–HIF1α network with positive feedback (Fig. 6F).