Silencing of IKKε expression inhibits migration and invasion abilities of SK-BR-3 cells and MCF-7 cells. Cell migration was determined using Boyden transwell chambers. Forty-eight hours after the transfection with siRNA, (a) SK-BR-3 cells and (b) MCF-7 cells were suspended in serum-free medium and seeded on 24-well transwell plates. RPMI-1640 with 10% FBS was incubated in the lower chamber as the chemoattractant. Cells migrated though pores to the bottom surface of the transwell were fixed with 10% buffered formalin, stained with 0.2% crystal violet and counted. Six random microscopic fields were counted for each group. Cell invasion was assayed in transwell coated with Matrigel. Cells crossed the Matrigel-coated filter were fixed, stained and counted. Representative pictures of the bottom surface are shown. Six random microscopic fields were counted for each group. The results presented are an average of six random microscopic fields from three independent experiments. Significant reduction of migration and invasion was observed after silencing IKKε expression in SK-BR-3 cells and MCF-7 cells. *P < 0.05. NC, negative control siRNA.