Silencing of Smurf2 expression inhibits migration and invasion abilities of MDA-MB-231 and MCF-7 cells. Cell migration was determined using Boyden transwell chambers. Forty-eight hours after the transfection with siRNA, (A) MDA-MB-231 cells and (B) MCF-7 cells were suspended in serum-free medium and seeded on 24-well transwell plates. Cells migrated though pores to the bottom surface of the transwell were fixed with with 10% formaldehyde, and stained with 0.5% crystal violet and counted. Six random microscopic fields were counted for each group. Cell invasion was assayed in transwell coated with Matrigel. Invaded cells were fixed, stained and counted. Six random microscopic fields were counted for each group. All experiments were performed in triplicates and repeated three times. Significant reduction of migration and invasion was observed after silencing Smurf2 expression in MDA-MB-231 and MCF-7 cells. (C), (D) The number of migrated or invaded cells of MDA-MB-231 and MCF-7 were counted from five or six randomly selected fields in a blind way and the result represented as mean ± standard deviation (n = 3). *P < 0.05 compared with control siRNA. NC, negative control without siRNA.