Abstract
FLT3-ITD and FLT3-TKD are the most frequent tyrosine kinase mutations in acute myeloid leukemia (AML), with the former associated with poor prognosis. Here, we show that the PI3K inhibitor GDC-0941 or the Akt inhibitor MK-2206 induced apoptosis through the mitochondria-mediated intrinsic pathway more efficiently in hematopoietic 32D cells driven by FLT3-TKD (32D/TKD) than FLT3-ITD (32D/ITD), which robustly activated STAT5. The resistance to GDC-0941 and MK-2206 was gained by expression of the constitutively activated STAT5 mutant STAT5A1*6 in 32D/TKD cells, while it was abrogated by the STAT5 inhibitor pimozide in 32D/ITD cells or FLT3-ITD-expressing human leukemic MV4-11 cells. GDC-0941 or MK-2206 induced dephosphorylation of 4EBP1 more conspicuously in 32D/TKD than in 32D/ITD, which was prevented or augmented by STAT5A1*6 or pimozide, respectively, and correlated with downregulation of the eIF4E/eIF4G complex formation and Mcl-1 expression. Furthermore, exogenous expression of Mcl-1 endowed resistance to GDC-0941 and MK-2206 on 32D/TKD cells. Finally, it was confirmed in primary AML cells with FLT3-ITD that pimozide enhanced 4EBP1 dephosphorylation and Mcl-1 downregulation to augment cytotoxicity of GDC-0941. These data suggest that the robust STAT5 activation by FLT3-ITD protects cells treated with the PI3K/Akt pathway inhibitors from apoptosis by maintaining Mcl-1 expression through the mTORC1/4EBP1/eIF4E pathway.
Keywords:
AML; FLT3; MCL-1; PI3K; STAT5.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Adaptor Proteins, Signal Transducing
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Animals
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Apoptosis / drug effects
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Carrier Proteins / metabolism
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Caspase 9 / metabolism
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Cell Cycle Proteins
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Cell Line, Tumor
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Cell Proliferation
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Cell Survival
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Enzyme Activation
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Eukaryotic Initiation Factor-4E / metabolism
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Eukaryotic Initiation Factor-4G / metabolism
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Eukaryotic Initiation Factors
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Heterocyclic Compounds, 3-Ring / pharmacology
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Humans
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Indazoles / pharmacology
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Leukemia, Myeloid, Acute / pathology*
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Mice
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Mitochondria / metabolism
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Myeloid Cell Leukemia Sequence 1 Protein / metabolism*
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Phosphoinositide-3 Kinase Inhibitors
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Phosphoproteins / metabolism
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Phosphorylation / drug effects
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Pimozide / pharmacology
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Proto-Oncogene Proteins c-akt / antagonists & inhibitors
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STAT5 Transcription Factor / antagonists & inhibitors
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STAT5 Transcription Factor / genetics
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STAT5 Transcription Factor / metabolism*
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Sulfonamides / pharmacology
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TOR Serine-Threonine Kinases / metabolism
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fms-Like Tyrosine Kinase 3 / metabolism*
Substances
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2-(1H-indazol-4-yl)-6-(4-methanesulfonylpiperazin-1-ylmethyl)-4-morpholin-4-ylthieno(3,2-d)pyrimidine
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Adaptor Proteins, Signal Transducing
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Carrier Proteins
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Cell Cycle Proteins
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Eif4ebp1 protein, mouse
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Eif4g1 protein, mouse
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Eukaryotic Initiation Factor-4E
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Eukaryotic Initiation Factor-4G
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Eukaryotic Initiation Factors
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Heterocyclic Compounds, 3-Ring
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Indazoles
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MK 2206
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Mcl1 protein, mouse
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Myeloid Cell Leukemia Sequence 1 Protein
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Phosphoinositide-3 Kinase Inhibitors
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Phosphoproteins
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STAT5 Transcription Factor
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Stat5a protein, mouse
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Sulfonamides
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eIF4E protein, mouse
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Pimozide
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mTOR protein, mouse
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Flt3 protein, mouse
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fms-Like Tyrosine Kinase 3
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Proto-Oncogene Proteins c-akt
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TOR Serine-Threonine Kinases
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Caspase 9