IFITM1 knockdown decreases migration and invasion in AI-resistant MCF-7:5C breast cancer cells. (A) MCF-7:5C cells were transfected with control siRNA (siCon) or IFITM1 siRNA (siIFITM1) for 24 hours and knockdown of IFITM1 protein expression was confirmed by Western blot (right panel) and real-time PCR analyses (left panel). Standard deviations are shown. **P <0.01 versus siCon. (B and C) The effect of IFITM1 knockdown on cell migration (B) and invasion (C) was assessed by transwell migration assay and matrigel invasion assay. Cells that invaded through the Matrigel-coated transwells were fixed, stained, visualized by light microscopy and photographed. Quantitation of the Transwell assay is also shown (B, right panel). Ten random fields were counted per insert at 20X. **P <0.01. (D) Effect of IFITM1 knockdown on cell viability in resistant MCF-7:5C cells. Cells were transfected with siCon or siIFITM1 for 24 hours, then DNA content of cells was analyzed using flow cytometry as described in the Methods section. The arrow is sub G1 phase apoptosis. MTT assay (bottom panel) was also performed in the IFITM1-knockdown cells at 24 hours. All the illustrated data are expressed as mean values of three independent experiments. Standard deviations are shown. AI, aromatase inhibitor; IFITM1, interferon induced transmembrane protein1; MTT, 3-(4,5-dimethylthiazol-2-Yl)-2,5-diphenyltetrazolium bromide.