FGFR1 and glioblastoma: While GC1 and GC2 reflect clinically relevant MGMT-unmethylated GBM subtypes, additional studies across a broader panel of primary GSCs and patient-derived xenografts are needed to confirm the generalizability of these findings and to better define the subset of GBM patients most likely to benefit from FGFR1-targeted radiosensitization.