In PTEN-deficient solid cancers (of the brain, breast and prostate), isoform specific RNA interference identified PI3Kβ as essential for cellular growth [53], but in PTEN deficient T-ALL subtype specific in vitro inhibition of PI3Kβ failed to effectively inhibit downstream signaling of the PI3K/AKT/mTOR network [54]. Here, AKT1 is linked to acute lymphoblastic leukemia.