Figure 4

Activation of integrin β1 and ERK1/2 is essential for syntenin-induced migration and invasion. (A) Silencing of syntenin in MDA-MB-231HM cells inhibited active integrin β1 expression and phosphorylation of ERK1/2, but had no effects on JNK and p38. (B) Overexpression of syntenin increased active integrin β1 expression and ERK1/2 phosphorylation in 231-SYN cells. The activation of ERK1/2 was analyzed with Western blot by using phosphor-specific antibodies. (C) Integrin β1 functional blocking antibody blocked both active integrin β1 expression and ERK1/2 phosphorylation. Cells were treated with integrin β1 or nonspecific IgG for 1 hour before protein extraction. (D) ERK1/2 inhibitor U0126 blocked activation of ERK1/2. Cells were pretreated with dimethylsulfoxide (DMSO) or 20 µM U0126 (U0126) for 2 hours before protein extraction. (E, F) U0126 effectively reduced the migration and invasion of breast cancer cells. GAPDH was used as loading control. Data are expressed as means of triplicate samples from three independent experiments; bars, SD. **P < 0.01; ***P < 0.001.