MTOR and glioblastoma: Although genes related to polyamine catabolism, such as SAT1, AOC1, RACK1, and PAOX, showed the highest expression in GBM tissues and the lowest expression in normal tissues, most of the polyamine biosynthesis-related genes had remarkably increased expression levels in GBM samples, except methylthioadenosine phosphorylase (MTAP), AZIN2, AZIN1, SMOX, MTOR, and MYC. The expression of polyamine transport-related genes increased or decreased with the increasing degree of malignancy (Figures 1A, B).