Integrin β1 mediates PRL-3-induced ERK1/2 activation. (A) Knockdown of integrin β1 abolished PRL-3-induced ERK1/2 phosporylation. LoVo-P cells were treated with siRNA against integrin β1 or control for 72 h, and then lysates (50 μg of protein) were subjected to Western blot to analyze the expression of p-ERK1/2, ERK1/2, Myc-tag (for Myc-PRL-3), integrin β1, and β-actin (B) U0126 inhibited PRL-3-induced ERK1/2 phosporylation in a dose-dependent manner. Twenty-four hours after plating, LoVo-C and LoVo-P cells were treated with indicated concentration of U0126 for 1 h, and their lysates (50 μg of protein) were analyzed for p-ERK1/2, ERK1/2 and Myc-tag (for Myc-PRL-3) by Western blot. (C) and (D) Inhibition of ERK1/2 activity by U0126 abolished PRL-3-induced cell motility and invasion. LoVo-C and LoVo-P cells were treated with 10 μM of U0126 for 1 h, and then subjected to motility and invasion assays as described in Figure 2B and 2C, respectively. Values were the total number of stained cells. The experiments were repeated at least three times independently. Error bars represent standard errors of the mean value (*, P < 0.05).