title: Novel B55α-PP2A mutations in AML promote AKT T308 phosphorylation and sensitivity to AKT inhibitor-induced growth arrest.
abstract: Activation of the Protein Kinase B (PKB), or AKT pathway has been shown to correlate with acute myeloid leukemia (AML) prognosis. B55α-Protein Phosphatase 2A (PP2A) has been shown to dephosphorylate AKT at Thr-308 rendering it inactive. In fact, low expression of the PP2A regulatory subunit B55α was associated with activated phospho-AKT and correlated with inferior outcomes in AML. Despite this fact, no studies have specifically demonstrated a mechanism whereby B55α expression is regulated in AML. In this study, we demonstrate novel loss of function mutations in the PPP2R2A gene identified in leukemic blasts from three AML patients. These mutations eliminate B55α protein expression thereby allowing constitutive AKT activation. In addition, leukemic blasts with PPP2R2A gene mutation were more sensitive to treatment with the AKT inhibitor MK2206, but less responsive to the PP2A activator FTY720. Using leukemia cell lines, we further demonstrate that B55α expression correlates with AKT Thr-308 phosphorylation and predicts responsiveness to AKT inhibition and PP2A activation. Together our data illustrate the importance of the B55α-PP2A-AKT pathway in leukemogenesis. Screening for disruptions in this pathway at initial AML diagnosis may predict response to targeted therapies against AKT and PP2A.
authors.affiliation: Division of Hematology/Oncology, Loma Linda University School of Medicine, Loma Linda, CA, USA.
authors.forename: Geoffrey
authors.initials: G
authors.lastname: Shouse
authors.affiliation: Loma Linda University Cancer Center, Biospecimen Laboratory, Loma Linda University School of Medicine, Loma Linda, CA, USA.
authors.forename: Rosalia
authors.initials: R
authors.lastname: de Necochea-Campion
authors.affiliation: Loma Linda University Cancer Center, Biospecimen Laboratory, Loma Linda University School of Medicine, Loma Linda, CA, USA.
authors.forename: Saied
authors.initials: S
authors.lastname: Mirshahidi
authors.affiliation: Department of Biochemistry, University of California, Riverside, Riverside, CA, USA.
authors.forename: Xuan
authors.initials: X
authors.lastname: Liu
authors.affiliation: Division of Hematology/Oncology, Loma Linda University School of Medicine, Loma Linda, CA, USA.|Loma Linda University Cancer Center, Biospecimen Laboratory, Loma Linda University School of Medicine, Loma Linda, CA, USA.
authors.forename: Chien-Shing
authors.initials: CS
authors.lastname: Chen
mesh_terms: D045744:Cell Line, Tumor; D049109:Cell Proliferation; D002470:Cell Survival; D003062:Codon; D004791:Enzyme Inhibitors / Q000494:pharmacology; D000068876:Fingolimod Hydrochloride / Q000494:pharmacology; D015973:Gene Expression Regulation, Leukemic; D006575:Heterocyclic Compounds, 3-Ring / Q000494:pharmacology; D006801:Humans; D016130:Immunophenotyping; D015470:Leukemia, Myeloid, Acute / Q000188:drug therapy / Q000235:genetics*; D009154:Mutation; D010766:Phosphorylation; D054648:Protein Phosphatase 2 / Q000235:genetics*; D051057:Proto-Oncogene Proteins c-akt / Q000037:antagonists & inhibitors / Q000235:genetics*
chemical_list: D003062:Codon; D004791:Enzyme Inhibitors; D006575:Heterocyclic Compounds, 3-Ring; C548887:MK 2206; C494918:AKT1 protein, human; D051057:Proto-Oncogene Proteins c-akt; C517189:PPP2CA protein, human; D054648:Protein Phosphatase 2; D000068876:Fingolimod Hydrochloride
keywords: AKT; B55α; acute myeloid leukemia; protein kinase B; protein phosphatase 2A