Constitutive NF-kappaB DNA-binding activity in AML is frequently mediated by a Ras/PI3-K/PKB-dependent pathway.
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.
Division of Hematology, Department of Medicine, University of Groningen, The Netherlands.
K U
KU
Birkenkamp
M
M
Geugien
H
H
Schepers
J
J
Westra
H H
HH
Lemmink
E
E
Vellenga
D000208:Acute Disease; D017209:Apoptosis; D002867:Chromones / Q000494:pharmacology; D004273:DNA, Neoplasm / Q000378:metabolism; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D017930:Genes, Reporter; D006133:Growth Substances / Q000378:metabolism; D006801:Humans; D007951:Leukemia, Myeloid / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D008715:Methionine / Q000031:analogs & derivatives* / Q000494:pharmacology; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D009025:Morpholines / Q000494:pharmacology; D009154:Mutation; D016328:NF-kappa B / Q000378:metabolism*; D015689:Oncogene Protein p21(ras) / Q000378:metabolism*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism; D015398:Signal Transduction; D014158:Transcription, Genetic; D014162:Transfection; D014407:Tumor Cells, Cultured; D051941:fms-Like Tyrosine Kinase 3
D002867:Chromones; D004273:DNA, Neoplasm; D004791:Enzyme Inhibitors; D006133:Growth Substances; D008715:Methionine; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D009025:Morpholines; D016328:NF-kappa B; D015689:Oncogene Protein p21(ras); D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D020794:Receptor Protein-Tyrosine Kinases; D051941:fms-Like Tyrosine Kinase 3; C096898:L 744832; C085911:2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one; C497970:FLT3 protein, human