Objectives: Constitutive signaling through the phosphatidylinositol-3-kinase-Akt-mammalian target of rapamycin (PI3K-Akt-mTOR) pathway is present in acute myeloid leukemia (AML) cells. The aim of the study was to compare constitutive PI3K-Akt-mTOR activation of primary AML cells for a large group of unselected patients.
Methods: We investigated expression and phosphorylation of 18 mediators in the PI3K-Akt-mTOR main track by flow cytometry for AML cells derived from 77 patients, and compared this with global gene expression profiles, proteomic, and transcriptomic profiles, and susceptibility to antileukemic agents.
Results: Patients were divided into two main subsets showing generally high or low constitutive pathway activation. The high activation subset was characterized by decreased frequency of cells showing monocytic differentiation, increased frequency of adverse karyotypes, decreased constitutive cytokine release, and increased expression of certain integrins. Finally, the two groups differed in their expression of genes encoding regulators of protein phosphorylation, whereas phosphoproteomic analyses showed differences especially with regard to transcriptional regulation. Antiproliferative effects of pathway inhibition were generally stronger for the low phosphorylation subset.
Conclusion: The constitutive PI3K-Akt-mTOR activation differed between patients; this difference appears to be a part of complex phenotypic differences including cell communication, intracellular signaling through other pathways, and transcriptional regulation.
Keywords: Acute myeloid leukemia; Akt; PI3K; cell signaling; mTOR; phosphorylation.