Constitutive activation of NF-kappaB in Ki-ras-transformed prostate epithelial cells.
The signaling pathway responsible for the activation of nuclear factor-kappaB (NF-kappaB) by oncogenic forms of Ras remains unclear. Both, the transactivation and DNA binding activities of NF-kappaB, were increased in 267B1 human prostate epithelial cells transformed by viral Kirsten-ras (267B1/Ki-ras cells) compared with those in the parental cells. This increased NF-kappaB activity was attributed to a heterodimeric complex of p50 and p65 subunits. Although the abundance of the inhibitor protein IkappaBbeta was higher in 267B1/Ki-ras cells than in 267B1 cells, an electrophoretic mobility-shift assay suggested that IkappaBalpha is responsible for the activation of NF-kappaB in the former cells. Consistent with this notion, the phosphorylation of IkappaBalpha appeared increased in 267B1/Ki-ras cells, and the proteasome inhibitor I abolished the constitutive activation of NF-kappaB in these cells. The expression of dominant negative mutants of either NIK (NF-kappaB-inducing kinase) or IKKbeta (IkappaB kinase beta) inhibited the activity of NF-kappaB in 267B1/Ki-ras cells. Furthermore, chemical inhibitors specific for Ras activation, sulindac sulfide and farnesytranferase inhibitor I, markedly reduced IkappaBalpha phosphorylation and NF-kappaB activation in the Ki-ras-transformed cells while transfection of these cells with NIK or IKKbeta counteracted the inhibitory effect on NF-kappaB activation. These results suggest that oncogenic Ki-Ras induces transactivation of NF-kappaB through the NIK-IKKbeta-IkappaBalpha pathway.
Kim
Bo-Yeon
BY
Department of Radiation Medicine, Georgetown University School of Medicine, Washington DC 20007, USA.
Gaynor
Richard B
RB
Song
Kyung
K
Dritschilo
Anatoly
A
Jung
Mira
M
D002471:Cell Transformation, Neoplastic; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000378:metabolism; D024202:Electrophoretic Mobility Shift Assay; D004847:Epithelial Cells / Q000378:metabolism* / Q000473:pathology*; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D020672:I-kappa B Proteins; D008297:Male; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B / Q000378:metabolism*; D015689:Oncogene Protein p21(ras) / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D011467:Prostate / Q000378:metabolism* / Q000473:pathology*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D000097782:NF-kappaB-Inducing Kinase
D004268:DNA-Binding Proteins; D020672:I-kappa B Proteins; D000072000:NF-KappaB Inhibitor alpha; D016328:NF-kappa B; D015689:Oncogene Protein p21(ras); D017346:Protein Serine-Threonine Kinases; D000097782:NF-kappaB-Inducing Kinase; C083487:I kappa B beta protein; C000606204:NFKBIA protein, human