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The constitutive activation of the phosphatidylinositol 3-kinase (PI3K)/Akt pathway commonly occurs in cancers and is a crucial event in tumorigenesis. Chronic myelogenous leukemia (CML) is characterized by a reciprocal chromosomal translocation (9;22) that generates the Bcr-Abl fusion gene. The PI3K/Akt pathway is activated by Bcr-Abl chimera protein and mediates the leukemogenesis in CML. However, the mechanism by which Bcr-Abl activates the PI3K/Akt pathway is not completely understood. In the present study, we found that pleckstrin homology domain leucine-rich repeat protein phosphatases 1 and 2 (PHLPP1 and PHLPP2) were depleted in CML cells. We investigated the interaction between PHLPPs and Bcr-Abl in CML cell lines and Bcr-Abl+ progenitor cells from CML patients. The Abl kinase inhibitors and depletion of Bcr-Abl induced the expression of PHLPP1 and PHLPP2, which dephosphorylated Ser-473 on Akt1, -2, and -3, resulting in inhibited proliferation of CML cells. The reduction of PHLPP1 and PHLPP2 expression by short interfering RNA in CML cells weakened the Abl kinase inhibitor-mediated inhibition of proliferation. In colony-forming unit-granulocyte, erythroid, macrophage, megakaryocyte; colony-forming unit-granulocyte, macrophage; and burst-forming unit-erythroid, treatment with the Abl kinase inhibitors and depletion of Bcr-Abl induced PHLPP1 and PHLPP2 expression and inhibited colony formation of Bcr-Abl+ progenitor cells, whereas depletion of PHLPP1 and PHLPP2 weakened the inhibition of colony formation activity by the Abl kinase inhibitors in Bcr-Abl+ progenitor cells. Thus, Bcr-Abl represses the expression of PHLPP1 and PHLPP2 and continuously activates Akt1, -2, and -3 via phosphorylation on Ser-473, resulting in the proliferation of CML cells.
Fusion Proteins, bcr-abl, Nuclear Proteins, HL-60 Cells, U937 Cells, Gene Expression Regulation, Neoplastic, Phosphatidylinositol 3-Kinases, Cell Line, Tumor, Leukemia, Myelogenous, Chronic, BCR-ABL Positive, Phosphoprotein Phosphatases, Humans, Protein Isoforms, Phosphorylation, K562 Cells, Proto-Oncogene Proteins c-akt, Cell Proliferation
Fusion Proteins, bcr-abl, Nuclear Proteins, HL-60 Cells, U937 Cells, Gene Expression Regulation, Neoplastic, Phosphatidylinositol 3-Kinases, Cell Line, Tumor, Leukemia, Myelogenous, Chronic, BCR-ABL Positive, Phosphoprotein Phosphatases, Humans, Protein Isoforms, Phosphorylation, K562 Cells, Proto-Oncogene Proteins c-akt, Cell Proliferation
citations This is an alternative to the "Influence" indicator, which also reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically). | 26 | |
popularity This indicator reflects the "current" impact/attention (the "hype") of an article in the research community at large, based on the underlying citation network. | Top 10% | |
influence This indicator reflects the overall/total impact of an article in the research community at large, based on the underlying citation network (diachronically). | Top 10% | |
impulse This indicator reflects the initial momentum of an article directly after its publication, based on the underlying citation network. | Top 10% |