IDH1 and glioblastoma: To date, a variety of molecular biomarkers have been identified in GBM, including O6-methylguanine DNA methyltransferase (MGMT) gene promoter methylation, isocitrate dehydrogenase 1/2 (IDH1/2) mutations, telomerase reverse transcriptase (TERT) gene promoter mutations, and EGFR amplification or mutation.