Abstract
In the present study, we aimed to elucidate the mechanism responsible for constitutive NF-kappaB DNA-binding activity in AML cells. Intervening in aberrant signaling pathway provides a rational approach for in vivo targeting of AML cells. Constitutive NF-kappaB DNA-binding activity was observed in 16 of 22 (73%) investigated AML cases and was, in general, associated with resistance to spontaneous apoptosis. Indeed, inhibition of NF-kappaB activity by the NF-kappaB inhibitor SN-50 peptide resulted in enhanced chemotherapy-induced apoptosis. In the majority of cases, constitutive NF-kappaB activity was mediated by a Ras/PI3 kinase (PI3-K)/protein kinase B (PKB)-mediated pathway. The PI3-K inhibitor Ly294002 and the Ras inhibitor L-744832 both inhibited PKB phosphorylation and NF-kappaB DNA-binding activity. The constitutive activation of Ras GTP-ase was caused by mutations in the gene encoding for N-Ras in 29% of the cases. The constitutive NF-kappaB activity could so far not be ascribed to the autocrine production of growth factors or to mutations in the Flt3 receptor, since anti-GM-CSF, -IL-1, -IL6, -TNFalpha or the tyrosine kinase inhibitor AG1296 did not affect the NF-kappaB DNA-binding activity. The present study demonstrates that Ras activation is an important pathway for triggering the NF-kappaB pathway in AML cells.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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Acute Disease
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Apoptosis
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Chromones / pharmacology
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DNA, Neoplasm / metabolism
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Enzyme Activation
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Enzyme Inhibitors / pharmacology
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Genes, Reporter
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Growth Substances / metabolism
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Humans
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Leukemia, Myeloid / classification
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Leukemia, Myeloid / genetics
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Leukemia, Myeloid / metabolism*
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Methionine / analogs & derivatives*
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Methionine / pharmacology
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Mitogen-Activated Protein Kinase 1 / metabolism
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Mitogen-Activated Protein Kinase 3
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Mitogen-Activated Protein Kinases / metabolism
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Morpholines / pharmacology
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Mutation
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NF-kappa B / metabolism*
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Oncogene Protein p21(ras) / metabolism*
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Phosphatidylinositol 3-Kinases / metabolism*
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Phosphoinositide-3 Kinase Inhibitors
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Phosphorylation
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Protein Serine-Threonine Kinases*
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Proto-Oncogene Proteins / metabolism*
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Proto-Oncogene Proteins c-akt
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Receptor Protein-Tyrosine Kinases / metabolism
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Signal Transduction*
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Transcription, Genetic
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Transfection
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Tumor Cells, Cultured
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fms-Like Tyrosine Kinase 3
Substances
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Chromones
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DNA, Neoplasm
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Enzyme Inhibitors
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Growth Substances
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L 744832
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Morpholines
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NF-kappa B
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Phosphoinositide-3 Kinase Inhibitors
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Proto-Oncogene Proteins
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2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one
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Methionine
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FLT3 protein, human
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Receptor Protein-Tyrosine Kinases
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fms-Like Tyrosine Kinase 3
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Protein Serine-Threonine Kinases
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Proto-Oncogene Proteins c-akt
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Mitogen-Activated Protein Kinase 1
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Mitogen-Activated Protein Kinase 3
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Mitogen-Activated Protein Kinases
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Oncogene Protein p21(ras)