PTEN and glioblastoma: The various biomarkers, the use of which has become routine when clinically diagnosing glioblastoma patients, include O6-methylguanine DNA methyltransferase (MGMT) (21–24), IDH (25–28), EGFR (29–31), TERT (32–34), tumor suppressor protein (TP53) (9, 35), and phosphatase and tensin homolog (PTEN) (36, 37).