Inhibition by DHMEQ of NF-κB in rheumatoid arthritis fibroblast-like synoviocytes. Nuclear extracts were obtained from unstimulated and tumor necrosis factor (TNF)-α-stimulated rheumatoid arthritis (RA) fibroblast-like synoviocytes (FLS) and nuclear factor-κB (NF-κB) DNA-binding activity was examined by electrophoretic mobility shift assays. For supershift assays, the DNA-protein mixture was incubated with antibodies to p65, p50, or p52 before electrophoresis. To confirm the specificity of the assay, 100-fold excess of unlabeled NF-κB probe was included as a competitor. To assess whether dehydroxymethylepoxyquinomicin (DHMEQ) inhibits NF-κB activation in RA FLS, the cells were incubated with DHMEQ for 20 minutes before the stimulation with TNF-α. Data shown are representative of three independent experiments.