TP53 and glioblastoma: Several mechanisms underlying TMZ resistance in GBM have been described, including the expression of the repair enzyme O-6-methylguanine-DNA-methyltransferase (MGMT) [19, 20], loss of p53 function [21], selection of pre-existing TMZ-resistant cells [3], mitochondrial adaptive response [22], and dysregulation of glucose transporters and drug metabolism [23].