MTOR and central nervous system cancer: Interestingly, metabolites and enzymes that are components of this metabolism promote and enhance glioma cell malignancy and induce the activation of signaling pathways, including tyrosine kinase receptors (TKR)/PI3K/AKT/mTOR, TKR/Ras/RAF/MAPK/ERK and transcriptional factors (HIF-1, p53, and c-myc).