MTOR and acute lymphoblastic leukemia: PI3K–mTOR signalling allows the proper development of T cells and promotes the survival of developing T cells.59 PI3K pathway mutations are more prevalent in TAL1 cases in a T-ALL setting.18 Constitutive activation of the PI3K–mTOR pathway is commonly associated with inhibitory mutations to PTEN (~20%), PIK3R1 (~6%), and AKT1 (~2%) as well as deletion of the phosphatase PTPN2 (~5%).18,60–62