OBJECTIVETo investigate let-7c's effect on the proliferation of human hepatocellular carcinoma cell HCCLM3 by transient transfection and the mechanism inside.

METHODSLipofectamine 2000 was used to transfect miRNAs into HCCLM3 cells. The cells were divided into three groups, let-7c group: let-7c was transfected, negative control group: negative control miRNA was transfected, blank control group: nothing was transfected. The proliferation of HCCLM3 cells was evaluated using Cell Counting Kit-8 (CCK-8). The cell cycles of each group were assayed by flow cytometry. Western blot and Real time PCR were used to analyze the protein and mRNA expressions of cyclin D1. Statistical analysis was performed with SPSS 17.0.

RESULTSThe absorbances of let-7c group were 0.70 ± 0.05, 0.77 ± 0.09 at 48 h and 72 h after transfection, lower than that of blank control group (0.97 ± 0.10, 1.21 ± 0.12) and negative control group (0.91 ± 0.07, 1.12 ± 0.09), 48 h: F = 14.431, P < 0.05, 72 h: F = 21.146, P < 0.05. The flow cytometry at 72 h after transfection revealed that let-7c increased the percentage of cells in G1 phase. The percentage of blank control group was 43.53% ± 0.86%, the negative control group was 44.82% ± 0.77%, and the let-7c group was 54.52% ± 0.13%, F = 240.739, P < 0.05. let-7c suppressed expressions of cyclin D1 at both protein and mRNA levels. The protein levels of cyclin D1 were 0.48 ± 0.09, 0.47 ± 0.06 and 0.23 ± 0.06 (F = 11.316, P < 0.05) in blank control group, negative control group and let-7c group, respectively. The mRNA levels were 1.03% ± 0.29%, 1.01% ± 0.11% and 0.63% ± 0.14% (F=6.315, P < 0.05) in the above three groups, respectively.

CONCLUSIONLet-7c can inhibit proliferation of HCCLM3 cells and increase the proportion of cells in G1 phase. The mechanism may be that let-7c represses the expressions of cyclin D1 at both protein and mRNA levels.