Silencing of IKKε expression reduces basal NF-κB transcriptional activity in SK-BR-3 cells and MCF-7 cells. Twenty-four hours after the siRNA transfection, (a) SK-BR-3 cells and (b) MCF-7 cells were co-transfected with the NF-κB Met Luc2 reporter vector, which contains the NF-κB promoter element upstream of the luciferase gene, and the β-galactosidase reporter vector as an internal control. The expression of luciferase was used to monitor the transcriptional activity of NF-κB. The relative luciferase activity was normalized with the β-galactosidase expression. Result representative of three independent experiments. * P < 0.05. NC, negative control siRNA; RLU, Relative Luminescence Unites.