MiR-21 Regulated STAT3 Expression In Human Breast Cancer MCF-7 Cells

Objective: To identify expressions of miR-21 and STAT3 in human breast cancer MCF-7 cells and explore the role of miR-21 which may regulate expression of STAT3.Methods:MCF-7 cells were cultured(37 °C,5% CO2)in DMEM medium containing10% inactivated fatal bovine serum.On the forth day,culture medium was changed and floating cells were removed.Adherent cells gaining 80% confluence were passaged with the use of 0.25% trypsin.Cell morphology was observed by phase contrast microscope and the expression of STAT3 in MCF-7 cells was determined by immunofluorescence cytochemistry.MiR-21 which may regulate expression of STAT3 was predicted by miRanda and Target Scan.After transfection of miR-21 mimics into cells,the expressions of miR-21 and STAT3 were determined by q RT-PCR and western blot in the mimics group and the control group.Results: MCF-7 cells displayed short pyramidal morphology with uniform distribution under the phase contrast microscope.The expression of STAT3 was positive by immunofluorescence cytochemistry.To find the role of miR-21 targeting STAT3 3'UTR,we predicted using miRanda and Target Scan.miR-21 had one target site broadly conserved among vertebrates on STAT3 m RNA 3'UTR.MiRanda showed the mir SVR score of miR-21 was-0.7660 and Target Scan displayed seed match of miR-21 was 7mer-m8 and context+ score percentile was 95.Those all indicated miR-21 was well complementary with the target site of STAT3 gene.The result of q RT-PCR showed that expression of miR-21 in the mimics group was(21.08±7.48)fold higher than that in the control group(P<0.05)and expression of STAT3 m RNA in the mimics group was(0.4997±0.0862)fold lower than that in the control group(P<0.05).The result of western blot showed expression of STAT3 protein in the mimics group was(0.46±0.11)lower than that(0.83±0.17)in the control group(P<0.05).Over-expression of miR-21 down-regulated expression of STAT3 m RNA and protein.Conclusion: MiR-21 may negatively regulate STAT3 expression in human breast cancer MCF-7 cells.