A selective small-molecule nuclear factor-κB inhibitor from a high-throughput cell-based assay for activator protein-1 hits

NSC 676914 has been identified as a selective nuclear factor-kappa B (NF-kappa B) inhibitor that does not inhibit cell proliferation. This compound was originally identified in a high-throughput cell-based assay for activator protein-1 (AP-1) inhibitors using synthetic compound libraries and the National Cancer Institute natural product repository. NSC 676914 shows activity against NF-kappa B in luciferase reporter assays at concentrations much less than the IC50 for AP-1. A serum response element reporter used as a specificity control and indicator of cell proliferation was relatively insensitive to the compound. Pretreatment with NSC 676914 is here shown to repress 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced I kappa B-alpha phosphorylation and translocation of p65/50 to the nucleus but not the processing of p52 from p100, suggesting the inhibition of NF-kappa B regulator IKK beta rather than IKK alpha. Inhibition of NF-kappa B activation occurred as a consequence of blocking phosphorylation of IKK. Induction of I kappa B-alpha phosphorylation by TPA was diminished by pretreatment of NSC 676914 even at 1.1 mu mol/L. In contrast, kinases c-Jun-NH2-kinase and extracellular signal-regulated kinases 1 and 2, important for AP-1 activation, showed no significant repression by this compound. Furthermore, a Matrigel invasion assay with breast cancer cell lines and a transformation assay in mouse JB6 cells revealed that TPA-induced invasion and transformation responses were completely repressed by this compound. These results suggest that NSC 676914 could be a novel inhibitor having potential therapeutic activity to target NF-kappa B for cancer treatment or prevention. [Mol Cancer Ther 2009;8(3):571 - 81]