Silencing of Smurf2 inhibits focus formation. Forty-eight hours after the siRNA transfection, (A) MDA-MB-231 cells and (B) MCF-7 cells were seeded in six-well plates, and the medium was changed every 2 days. Cells cultured for 14 days were washed twice with 1xPBS, fixed by 4% paraformaldehyde, and stained with 0.5% crystal violet. Images of the colonies were obtained with a digital camera. (C), (D) Foci containing ≥50 cells were counted for MDA-MB-231 and MCF-7 cells and the result represented as mean ± standard deviation (n = 3). *P < 0.05 compared with control siRNA. NC-Negative control without siRNA.