Research Papers:

Novel B55α-PP2A mutations in AML promote AKT T308 phosphorylation and sensitivity to AKT inhibitor-induced growth arrest

Geoffrey Shouse _, Rosalia de Necochea-Campion, Saied Mirshahidi, Xuan Liu and Chien-Shing Chen

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Oncotarget. 2016; 7:61081-61092. https://doi.org/10.18632/oncotarget.11209

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Geoffrey Shouse1, Rosalia de Necochea-Campion2, Saied Mirshahidi2, Xuan Liu3, Chien-Shing Chen1,2

1Division of Hematology/Oncology, Loma Linda University School of Medicine, Loma Linda, CA, USA

2Loma Linda University Cancer Center, Biospecimen Laboratory, Loma Linda University School of Medicine, Loma Linda, CA, USA

3Department of Biochemistry, University of California, Riverside, Riverside, CA, USA

Correspondence to:

Geoffrey Shouse, email: [email protected]

Keywords: acute myeloid leukemia, AKT, protein kinase B, B55α, protein phosphatase 2A

Received: February 21, 2016     Accepted: July 27, 2016     Published: August 11, 2016


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.

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