EPO and glioblastoma: Besides increasing their migratory ability to survive the adverse hypoxic conditions, GBM cells implement several other changes, such as (i) switching from aerobic to anaerobic metabolism [22,23]; (ii) promoting the selection and maintenance of the more aggressive glioblastoma stem cells [24,25,26]; (iii) upregulating a second form of HIF, HIF-2, which increases erythropoietin production in the kidney and liver, resulting in increased hemoglobin synthesis [27] and endowing GBM cells with properties that help them to evade apoptotic death [28].