TERT and glioblastoma: Primary GBM is caused by several factors, including overexpression of MDM2 (Mouse double minute 2), mutation of EGFR (epidermal growth factor receptor), p16 deletion, TERT (telomerase reverse transcriptase) promoter mutation, and loss of heterozygosity of chromosome 10q holding PTEN (phosphatase and tensin Homolog) [22,23].