MGMT and neoplasm: Notably, xenograft mouse models of human GBM cells have demonstrated that post-TMZ administration, the majority of residual, treatment-resistant tumor cells were fluorescently labeled GSCs with the ability to reinitiate GBM.6 In addition, CD133+ GSCs exhibit higher levels of MGMT mRNA and lower expressions of autophagy- and apoptotic-related proteins that allow them to evade conventional therapies (Figure 2).52–54