MMP-2 and MMP-9 were essential for mediating PP4C-induced cell invasion. (A) The protein expression levels of MMP-2 and MMP-9 were detected by immunoblotting in SW480 and HT29 cells overexpressing PP4C. (B) Immunoblotting of MMP-2 and MMP-9 expression in SW620 and LOVO cells expressing lentiviral PP4C shRNA. (C, D) Conditioned medium from SW480 and HT29 cells overexpressing PP4C was collected and evaluated using the MMP gelatinase activity assay. (E, F) SW480 and HT29 cells overexpressing PP4C were pretreated with the MMP inhibitor GM6001 (25), a MMP-2 neutralizing antibody (Anti-MMP2) or a MMP-9 neutralizing antibody (Anti-MMP9) for 30 min, and the cell invasion was then determined using Matrigel invasion assay. *P < 0.05 and **P < 0.01 compared with the vector controls.