Background and purpose: MicroRNA-340 (miR-340) has been demonstrated to play a role of negative regulation in many kinds of tumor

however

there are few reports about the relationship between miR-340 in proliferation and apoptosis of breast cancer cell. This study was aimed to explore the effect of miR-340 on proliferation and apoptosis of breast cancer cell MDA-MB231. Methods: The pre-miR-340 or anti-miR-340 were transiently transfected into breast cancer cell MDA-MB231 with LipofectamineTM2000. miR-340 level was detected by RT-PCR. The Western blot was performed to detect the protein level of cleaved-caspase-3. The inhibition rate of cell proliferation was evaluated by MTT assay. The cell apoptosis was studied by flow cytometry. Results: The pre-miR-340 facilitated the expression of miR-340 in MDA-MB231 cells. The pre-miR-340 enhanced the protein level of cleaved-caspase-3

inhibited the proliferation of MDA-MB231 cells and increased its apoptosis. On the contrary

the expression of miR-340 was inhibited by anti-miR-340 in MDA-MB231 cells. The protein level of cleaved-caspase-3 was reduced after the antimiR-340-transfected MDA-MB231 cells. Anti-miR-340 promoted the proliferation of MDA-MB231 cells. Decreased apoptosis of MDA-MB231 cells was observed by flow cytometry. Conclusion: The overexpression of miR-340 can effectively inhibit the proliferation and increase the apoptosis of MDA-MB231 cells

which may be explained by upregulating of protein cleaved-caspase-3 level.