Overexpression of Notch1 activated Rac1 and promoted cell migration. (A) ICC-9810 cells were transfected with empty vector or Notch1, respectively. 48 h after transfection, the amount of active GTP-bound Rac1 was determined by antibodies specific for Rac1. (B) For Boyden chamber motility assay, cells were seeded onto the filter in the upper compartment of the chamber and incubated for 18 h. Cells passing through the pores were counted in five non-overlapping × 40 fields and photographed. *P < 0.05 vs vector transfected cells. (C) The activity of Rac1 after transfection 48 h. (D) The number of cells penetrated through the chamber in Migration assay. Notch1 transfected cells high expressed Notch1 compared with the cells in the control group. The number of cells penetrated through the chamber increased obviously. To prove that the increase of cells penetrated through the chamber was caused by the ability of cell migration, rather than cell proliferation, we also employed BrdU incorporation analysis to assay for cell proliferation. *P < 0.05 vs vector transfected cells. Data are expressed as mean ± SD of three independent experiments.