title: Survival of acute myeloid leukemia cells requires PI3 kinase activation.
abstract: The mechanisms that regulate the growth and survival of acute myeloid leukemia (AML) cells are largely unknown. We hypothesized that constitutive activation of phosphatidyl-inositide 3 kinase (PI3 kinase) could regulate survival in primary cells from patients with AML. Here we demonstrate that Akt, a critical substrate of PI3 kinase, is activated in AML blasts. In a short-term culture system, most AML patient samples showed a dose-dependent decrease in survival after incubation with the PI3 kinase inhibitor LY294002. This decrease in survival was partially due to the induction of apoptosis. Furthermore, we have shown that p70 S6 kinase and 4EBP-1, downstream mediators of Akt signaling, also are phosphorylated in AML blasts. Phosphorylation of these proteins is inhibited by the mTOR inhibitor RAD001. Incubation of AML blasts with RAD001 induces only a small decrease in survival of the cells; however, when combined with Ara-C, RAD001 enhances the toxicity of Ara-C. These results demonstrate that constitutive activation of the PI3 kinase pathway is necessary for the survival of AML blasts and that targeting of this pathway with pharmacologic inhibitors may be of clinical benefit in treatment of AML.
authors.affiliation: Division of Hematology and Oncology, University of Pennsylnvania, Philadelphia, PA 19104, USA.
authors.forename: Qing
authors.initials: Q
authors.lastname: Xu
authors.forename: Serge-Emile
authors.initials: SE
authors.lastname: Simpson
authors.forename: Timothy J
authors.initials: TJ
authors.lastname: Scialla
authors.forename: Adam
authors.initials: A
authors.lastname: Bagg
authors.forename: Martin
authors.initials: M
authors.lastname: Carroll
mesh_terms: D000208:Acute Disease; D000818:Animals; D002470:Cell Survival / Q000187:drug effects; D003561:Cytarabine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D004789:Enzyme Activation / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D000068338:Everolimus; D006801:Humans; D007951:Leukemia, Myeloid / Q000209:etiology* / Q000473:pathology*; D051379:Mice; D016513:Mice, SCID; D009374:Neoplasms, Experimental / Q000188:drug therapy / Q000473:pathology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D015398:Signal Transduction; D020123:Sirolimus / Q000031:analogs & derivatives / Q000494:pharmacology; D014183:Transplantation, Heterologous
chemical_list: D003561:Cytarabine; D004791:Enzyme Inhibitors; D000068338:Everolimus; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D020123:Sirolimus; C494918:AKT1 protein, human