OBJECTIVETo investigate the effects of microRNA(miRNA)-29b on the proliferation and migration of breast cancer cells and its molecular mechanism.

METHODSThe recombinant lentiviral expression vector (lenti-miRNA-29b) was constructed and transfected into 293T cells to obtain lentivirus particles that were used to infect breast cancer MCF-7 cells. Transfection efficiency of lenti-miRNA-29b in MCF-7 cells was identified by the expression of green fluorescent protein (GFP). The expression of miRNA-29b was detected by real-time PCR. The cell proliferation and migration were detected by CCK8 assay and Transwell assay, respectively. The bioinformatics softwares were used to predict and screen the downstream target genes regulated by miRNA-29b, which were verified by double luciferase reporter gene assay, RT-PCR and Western blot. The effects of screened target gene RTKN on the growth and migration of MCF-7 cells were verified by RTKN siRNA.

RESULTSRecombinant lentiviral expression vector of miRNA-29b were successfully constructed. About 90% and 60% of the breast cancer cells showed green fluorescence in lenti-miRNA-29b and lenti-miRNA-NC groups, respectively. The expression of miRNA-29b in lenti-miRNA-29b group increased significantly compared with the lenti-miRNA-NC group and blank control group (all<0.05); the proliferation and migration ability of MCF-7 cells significantly reduced compared with the control group (all<0.05). The screening with bioinformatics softwares found that the 3'UTR coding region RTKN had the binding site to miRNA-29b; the dual luciferase reporter gene assay showed that the luciferase activity decreased significantly after the MCF-7 cells were co-transfected with wild type RTKN-WT-3'UTR and miRNA-29b mimics report gene vector (<0.05). The RTKN proteins in MCF-7 cells were significantly decreased after transfection with siRNA-RTKN, and the proliferation and migration ability of MCF-7 cells were significantly reduced (all<0.05).

CONCLUSIONSMiRNA-29b can inhibit the proliferation, invasion and metastasis of breast cancer cells by inhibiting the expression of RTKN.