Nuclear factor-kappaB is constitutively active in C-cell carcinoma and required for RET-induced transformation.
Specific point mutations of the RET proto-oncogene have been demonstrated to be responsible for multiple endocrine neoplasia (MEN) types 2A and 2B, for familial medullary thyroid carcinoma (MTC) syndromes, as well as for sporadic MTC. Here we show that nuclear factor (NF)-kappaB is activated in RET-associated C-cell carcinoma specimens. TT cells, a human MTC cell line expressing MEN 2A type RET, display transcriptionally active RelA(p65) in the nucleus. NF-kappaB activity in these cells is attributable to constitutive IkappaB kinase (IKK) activity and high turn over of IkappaBalpha. RET harboring the mutations C634R (MEN 2A) or M918T (MEN 2B), in contrast to wild-type RET, activates a NF-kappaB-dependent reporter construct upon transient transfection in HeLa cells. We show that the prototype RET mutation C634R enhances phosphorylation of IkappaBalpha by IKKbeta but not by IKKalpha. RET-induced NF-kappaB and IKKbeta activity requires Ras function but does neither involve the classical mitogen-activated protein kinase kinase/extracellular signal-regulated kinase nor the phosphoinositide 3-kinase/Akt pathways. In contrast, RET-induced NF-kappaB activity is dependent on Raf and MEKK1. Inhibition of constitutive NF-kappaB activity results in cell death of TT cells and blocks focus formation induced by oncogenic forms of RET in NIH 3T3 cells. These results suggest that RET-mediated carcinogenesis critically depends on IKK activity and subsequent NF-kappaB activation.
Ludwig
L
L
Department of Internal Medicine I, University of Ulm, Robert-Koch-Street 8, D-89081 Ulm, Germany.
Kessler
H
H
Wagner
M
M
Hoang-Vu
C
C
Dralle
H
H
Adler
G
G
Böhm
B O
BO
Schmid
R M
RM
D016475:3T3 Cells; D000111:Acetylcysteine / Q000031:analogs & derivatives* / Q000494:pharmacology; D000818:Animals; D017209:Apoptosis / Q000502:physiology; D018276:Carcinoma, Medullary / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D002467:Cell Nucleus / Q000378:metabolism; D002471:Cell Transformation, Neoplastic; D004273:DNA, Neoplasm / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism / Q000502:physiology; D019281:Dimerization; D029721:Drosophila Proteins; D005347:Fibroblasts / Q000166:cytology; D006801:Humans; D051550:I-kappa B Kinase; D020672:I-kappa B Proteins; D020935:MAP Kinase Signaling System / Q000502:physiology; D051379:Mice; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000502:physiology*; D051096:Proto-Oncogene Proteins c-ret; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics / Q000502:physiology*; D015398:Signal Transduction / Q000502:physiology; D013964:Thyroid Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D051996:Transcription Factor RelA; D014158:Transcription, Genetic / Q000502:physiology; D014407:Tumor Cells, Cultured; D018631:ras Proteins / Q000502:physiology
D004273:DNA, Neoplasm; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D020672:I-kappa B Proteins; C000715470:MAS1 protein, human; D016328:NF-kappa B; C000606204:NFKBIA protein, human; C000606205:Nfkbia protein, mouse; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D051996:Transcription Factor RelA; C067713:lactacystin; D000072000:NF-KappaB Inhibitor alpha; D051096:Proto-Oncogene Proteins c-ret; D020794:Receptor Protein-Tyrosine Kinases; C416649:Ret protein, Drosophila; C494999:Ret protein, mouse; D017346:Protein Serine-Threonine Kinases; C496559:CHUK protein, human; C496564:Chuk protein, mouse; D051550:I-kappa B Kinase; C496560:IKBKB protein, human; C496565:IKBKE protein, human; C496562:Ikbkb protein, mouse; C496566:Ikbke protein, mouse; D020928:Mitogen-Activated Protein Kinases; D018631:ras Proteins; D000111:Acetylcysteine