title: A novel NF-kappa B-inducing kinase-MAPK signaling pathway up-regulates NF-kappa B activity in melanoma cells.
abstract: Constitutive activation of NF-kappa B is an emerging hallmark of various types of tumors including breast, colon, pancreatic, ovarian, and melanoma. In melanoma cells, the basal expression of the CXC chemokine, CXCL1, is constitutively up-regulated. This up-regulation can be attributed in part to constitutive activation of NF-kappa B. Previous studies have shown an elevated basal I kappa B kinase (IKK) activity in Hs294T melanoma cells, which leads to an increased rate of I kappa B phosphorylation and degradation. This increase in I kappa B-alpha phosphorylation and degradation leads to an approximately 19-fold higher nuclear localization of NF-kappa B. However, the upstream IKK kinase activity is up-regulated by only about 2-fold and cannot account for the observed increase in NF-kappa B activity. We now demonstrate that NF-kappa B-inducing kinase (NIK) is highly expressed in melanoma cells, and IKK-associated NIK activity is enhanced in these cells compared with the normal cells. Kinase-dead NIK blocked constitutive NF-kappa B or CXCL1 promoter activity in Hs294T melanoma cells, but not in control normal human epidermal melanocytes. Transient overexpression of wild type NIK results in increased phosphorylation of extracellular signal-regulated kinases 1 and 2 (ERK1/2), which is inhibited in a concentration-dependent manner by PD98059, an inhibitor of p42/44 MAPK. Moreover, the NF-kappa B promoter activity decreased with overexpression of dominant negative ERK expression constructs, and EMSA analyses further support the hypothesis that ERK acts upstream of NF-kappa B and regulates the NF-kappa B DNA binding activity. Taken together, our data implicate involvement of I kappa B kinase and MAPK signaling cascades in NIK-induced constitutive activation of NF-kappa B.
authors.affiliation: Department of Veterans Affairs, Nashville, Tennessee 37212, USA.
authors.forename: Punita
authors.initials: P
authors.lastname: Dhawan
authors.forename: Ann
authors.initials: A
authors.lastname: Richmond
mesh_terms: D021581:Active Transport, Cell Nucleus; D002460:Cell Line; D004247:DNA / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005419:Flavonoids / Q000494:pharmacology; D006801:Humans; D020935:MAP Kinase Signaling System; D008545:Melanoma / Q000201:enzymology / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D008954:Models, Biological; D009154:Mutation; D016328:NF-kappa B / Q000378:metabolism*; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D015398:Signal Transduction; D013997:Time Factors; D014162:Transfection; D014407:Tumor Cells, Cultured; D015854:Up-Regulation
chemical_list: D004791:Enzyme Inhibitors; D005419:Flavonoids; D016328:NF-kappa B; D004247:DNA; D020928:Mitogen-Activated Protein Kinases; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one