GSC functions are largely mediated by several deregulated signaling pathways, such as MEK/ERK [296], Notch [297], NF-κB [298], Hh [299], WNT/β-catenin [300], PI3K/AKT/mTOR [301], JAK-STAT [302,303], retinoblastoma protein (Rb), receptor tyrosine kinase (RTK) [304], transforming growth factor-β (TGF-β), platelet-derived growth factor [305,306], and PTEN [307], resulting in an aberrant expression of downstream signature molecules that drive radioresistance and recurrence of GBM. The gene discussed is MTOR; the disease is glioblastoma.