MTOR and acute lymphoblastic leukemia: In all T-ALL sensitive cell lines, nelarabine treatment induced a marked decrease of phosphorylated AKT at Ser473, S6 ribosomal protein (S6RP) at Ser235/236, and GSK3β at Ser9 after 48 h of treatment, suggesting that PI3K/AKT/mTOR pathway is down-modulated by nelarabine (Fig. 2c).