MGMT and glioblastoma: Heterogeneous expression of several other common genes, which include isocitrate dehydrogenase (IDH1), telomerase reverse transcriptase (TERT), phosphatase and tensin homologue (PTEN), neurofibromatosis type 1 (NF1) gene and O6-methylguanine-DNA methyltransferase (MGMT), have also been described within glioblastoma tumors [9].