MTOR and glioblastoma: Taking into account that GBM is characterized by an extremely heterogeneous cell population and that GSCs are reasonably responsible for GBM recurrence, we were also interested to understand the impact of mTOR on GSCs, also in light of the recent observation that mTOR activation is responsible for the increased expression of a stem cell phenotype in tumor cells and that environmental cues might reprogram tumor cells in stem-like cells (Xia and Xu, 2015; Jhanwar-Uniyal et al., 2017).