PTEN is a lipid phosphatase that antagonizes the PI3K-dependent phosphorylation of PtdIns4,5P2 (PIP2) into PtdIns3,4,5P3 (PIP3) needed for optimal activation of the AKT/mTOR-mediated pro-survival program [26] and is also one of the most frequently inactivated components of this pathway in T-ALL [27–30]. This evidence concerns the gene PTEN and acute lymphoblastic leukemia.