A selective small molecule NF-κB inhibitor from a high-throughput cell based assay for “AP-1 hits”

NSC 676914 has been identified as a selective NF-κB inhibitor that does not inhibit cell proliferation. This compound was originally identified in a high-throughput cell based assay for AP-1 inhibitors using synthetic compound libraries and the NCI natural product repository. NSC 676914 shows activity against NF-κB (Nuclear factor kappa B) in luciferase reporter assays at concentrations much less than the IC 50 for AP-1. An SRE (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 TPA-induced IκB-α phosphorylation and translocation of p65/50 to the nucleus, but not the processing of p52 from p100, suggesting inhibition of NF-κB regulator IKKβ rather than IKKα. Inhibition of NF-κB activation occurred as a consequence of blocking phosphorylation of IKK. Induction of IκB-α phosphorylation by TPA was diminished by pretreatment of NSC 676914 even at 1.1 µM. In contrast, kinases JNK and ERK1&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-κB for cancer treatment or prevention.