Flt-1 is required for PlGF-induced p38 phosphorylation, PlGF and Flt-1 were both important in promoting CRC cancer cell migration/invasion. siRNA (30 pmole/ml) inhibited Flt-1 expression and migratory ability in LoVo-PlGF cells as monitored by quantitative PCR (A) and migration assay (B). (C) Knockdown Flt-1 significantly attenuated p38 phopsphorylation in LoVo-PlGF. (D, E). The invasion ability of CRC cells decreased when PlGF was inhibited by siRNA. * indicated as P < 0.05.