Abstract
Hematopoietic growth factors (HGF) are essential for proliferation and differentiation of hematopoietic precursors and activate a distinct set of JAK-STAT (Janus kinases-signal transducers and activators of transcription) proteins. Previous results from our group have shown a strong expression of JAK-STAT proteins in primary acute myelogenous leukemia (AML) blasts and AML cell lines. Here, we asked whether a constitutive activation of the JAK-STAT pathway might be involved in the pathogenesis of AML. We could demonstrate a constitutive activation of STAT1, 3 and 5 by immunoprecipitation of the tyrosine phosphorylated proteins in different human AML cell lines. Three patterns of STAT activation were found: (I) activation of only STAT1, (II) activation of STAT1 in combination with STAT3, and (III) activation of STAT1, 3 and 5. Furthermore, STAT1 and 3 formed stable heterodimers only in cell lines with constitutive STAT3 activation. In all cell lines analyzed, tyrosine phosphorylation of the four known Janus kinases could not be detected, although JAK1 was stably associated with STAT3. To further analyze whether a constitutive activation of tyrosine kinases might contribute to the autonomous growth of AML blasts, inhibitor studies were performed. The tyrphostin AG490, an inhibitor of the JAK-STAT pathway, but not A1, an inactive tyrphostin induced a time- and dose-dependent growth arrest without overt morphological signs of differentiation in AML cell lines. Our results show that STAT transcription factors are constitutively activated in human AML cell lines and might contribute to the autonomous proliferation of AML blasts. Inhibition of this pathway might be of interest for the establishment of more specific antileukemic strategies.
Publication types
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Comparative Study
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Research Support, Non-U.S. Gov't
MeSH terms
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Acute Disease
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Alternative Splicing
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Cell Division / drug effects
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DNA-Binding Proteins / chemistry
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DNA-Binding Proteins / physiology*
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Dimerization
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Enzyme Activation
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Enzyme Inhibitors / pharmacology
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Gene Expression Regulation, Leukemic*
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Granulocyte Colony-Stimulating Factor / biosynthesis
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Granulocyte Colony-Stimulating Factor / genetics
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Granulocyte-Macrophage Colony-Stimulating Factor / biosynthesis
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Granulocyte-Macrophage Colony-Stimulating Factor / genetics
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HL-60 Cells / drug effects
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HL-60 Cells / metabolism
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Humans
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Interleukin-3 / biosynthesis
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Interleukin-3 / genetics
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Interleukin-6 / biosynthesis
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Interleukin-6 / genetics
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Janus Kinase 1
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K562 Cells / drug effects
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K562 Cells / metabolism
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Leukemia, Myeloid / genetics*
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Leukemia, Myeloid / pathology
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Milk Proteins*
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Neoplasm Proteins / chemistry
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Neoplasm Proteins / physiology*
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Phosphorylation
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Protein Processing, Post-Translational
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Protein-Tyrosine Kinases / antagonists & inhibitors
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Protein-Tyrosine Kinases / physiology
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Proteins / antagonists & inhibitors
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Proteins / physiology
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STAT1 Transcription Factor
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STAT3 Transcription Factor
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STAT5 Transcription Factor
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Signal Transduction / genetics
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TYK2 Kinase
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Trans-Activators / chemistry
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Trans-Activators / physiology*
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Transcription, Genetic / physiology*
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Tumor Cells, Cultured / drug effects
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Tumor Cells, Cultured / metabolism
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Tumor Necrosis Factor-alpha / biosynthesis
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Tumor Necrosis Factor-alpha / genetics
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Tyrphostins / pharmacology
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U937 Cells / drug effects
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U937 Cells / metabolism
Substances
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DNA-Binding Proteins
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Enzyme Inhibitors
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Interleukin-3
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Interleukin-6
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Milk Proteins
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Neoplasm Proteins
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Proteins
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STAT1 Transcription Factor
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STAT1 protein, human
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STAT3 Transcription Factor
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STAT3 protein, human
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STAT5 Transcription Factor
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Trans-Activators
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Tumor Necrosis Factor-alpha
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Tyrphostins
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alpha-cyano-(3,4-dihydroxy)-N-benzylcinnamide
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Granulocyte Colony-Stimulating Factor
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Granulocyte-Macrophage Colony-Stimulating Factor
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Protein-Tyrosine Kinases
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JAK1 protein, human
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Janus Kinase 1
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TYK2 Kinase
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TYK2 protein, human