Objective    To construct the IRF-4 binding protein (IBP) eukaryotic expression vector for RNA interference and to observe its effect on proliferation and invasion of MDA-MB-231 breast cancer cells.     Methods    Four pairs of recombinant vectors were designed and established using IBP as the target gene and plasmid pcDNA

TM

6.2-GW/EmGFPmiR as the vector

and the sequence of DNA was identified. After the recombinant plasmid was transfected into the cultured MDA-MB-231 cells

the most efficient expression vector was chosen to establish cell lines. Inhibitory effect of recombinant plasmid on expression of

IBP mRNA and protein was detected by real-time PCR and Western blotting

respectively. The inhibitory effect of recombinant plasmid on cell growth was detected by MTT assay. The invasion of MDA-MB-231 cells was identified by cell invasion assay.     Results    The sequence of recombinant plasmid was consistent with that of the designed vector. The expression of IBP mRNA and protein was decreased about 70% in recombinant expression vector transfected into MDA-MB-231 cells. The proliferation of breast cancer cells was reduced with the decreased expression of IBP (P0. 05). The invasion assay demonstrated that the number of breast cancer cells was significantly lower in transfection group than in non-transfected and blank control groups (25±7 vs 67±6 and 68±5

P0.05).     Conclusion    Down-regulation of IBP expression can significantly decrease the proliferation and invasion of breast cancer cells.