Knockdown of endogenous Notch1 inhibits Rac1 activity and cell migration. ICC-9810 cells were transfected with Notch1 siRNA or scramble siRNA (Control) (A). The ICN is sensitive to gamma-secretase inhibitor. Western blot analysis was employed to the ICN expression of ICC-9810 cells treatmented with 1 μmol/L of GSI. The results confirmed that ICN was induced at the protein level within 24 hours of exposure to the GSI but not by the DMSO control. Forty-eight hours after transfection, cell migration (B and C) and the Rac1 activity (D) were examined. *P < 0.05 vs. scramble siRNA-transfected cells. The data are expressed as the mean ± SD of three independent experiments.