Objective：To investigate the inhibitory effect of let-7a on human breast cancer cells in vitro and its possible mechanism.
Methods：Human breast cancer MCF-7 cells were transfected with let-7a(experimental group) and siRNA(siRNA group) and lipofectamine(control group) by using lipofectamineTM2000. The cell transfection efficiency was observed by fluorescence microscope, cell proliferation inhibitory rate was measured using CCK-8 assay, mRNA expression of IMP-1 of each group was detected using semi-quantitive reverse transcription-polymerase chain reaction(RT-PCR), and the level of IMP-1 protein expressions was measured by Western blot 48 hours after transfection.
Results：The cell transfection was efficiency and no significant difference between the let-7a group and siRNA group. Let-7a inhibited the proliferation of MCF-7 cells in a dose-and time-dependent manner(both P＜0.05). Apoptotic index in let-7a group was obviously higher than that in the siRNAgroup and control groups(both P＜0.05). The expression of IMP-1 mRNA in let-7a group was significantly lower than those in the siRNA group and control group（P＜0.01）. Expression of IMP-1 protein in MCF-7 cells was confirmed and it was clear that the specific band in let-7a group was obviously weaker than that in siRNA group and control groups.
Conclusions： let-7a can inhibit the proliferation of MCF-7 cells by reducing the IMP-1 gene expression in vitro.