Abstract: Objective: To investigate the effect of miR-302b-3p on the proliferation and apoptosis of the esophageal cancer EC-109 cells,and to elucidate the related mechanism of miR-302b-3p inhibiting the proliferation and inducing apoptosis of the EC-109 cells. Methods: The esophageal cancer EC-109 cells and normal esophageal epithelium HET-1A cells were cultured in vitro.The expression levels of miR-302b-3p in the EC-109 cells and HET-1A cells were detected by real-time fluorescence quantitative PCR method.The EC-109 cells were transfected instantaneously and divided into blank control group(non-transfection),miR-NC group (transfected with negative control of miR-302b-3p mimics),miR-302b-3p group (transfected with miR-302b-3p mimics),anti-miR-NC group (transfected with negative control of miR-302b-3p inhibitor) and anti-miR-302b-3p group (transfected with miR-302b-3p inhibitor).The viabilities of the EC-109 cells in various groups were detected by MTT assay;the percentages of EC-109 cells at different cell cycles and the apoptotic rates of EC-109 cells were detected by flow cytometry;the expression levels of CyclinD1,CDK2,Bax,and Cleaved caspase-3 in the EC-109 cells in various groups were detected by Western blotting method;the luciferase activities of EC-109 cells in various groups were detected by double luciferase reporter gene assay and Western blotting method was used to detect the expression level of epithelial cell transformation sequence 2(ECT2) protein in the EC-109 cells in various groups. Results: Compared with the HET-1A cells,the expression level of miR-302b-3p in the EC-109 cells was significantly decreased (P<0.05). Compared with blank control group,the viability of EC-109 cells,the percentage of cells at S phase and the expression levels of CyclinD1 and CDK2 protein in the EC-109 cells in miR-302b-3p group were significantly decreased(P<0.05),while the percentage of the cells at G₀/G₁ phase,the apoptotic rate,and the expression levels of Bax and Cleaved caspase-3 proteins in the EC-109 cells were significantly increased(P<0.05).Compared with anti-miR-NC group, the cell viability,the percentage of the cells at S phase and the expression levels of Cyclin D1 and CDK2 protein in the EC-109 cells in anti-miR-302b-3p group were significantly increased(P<0.05),and the percentage of the cells at G₀/G₁ phase,the apoptotic rate and the expression levels of Bax and Cleaved caspase-3 proteins in the EC-109 cells were significantly decreased (P<0.05).Compared with miR-NC+ECT2-WT group,the luciferase activity of the EC-109 cells in miR-302b-3p+ECT2-WT group was decreased(P<0.05);compared with anti-miR-NC+ECT2-WT group,the luciferase activity of the EC-109 cells in anti-miR-302b-3p+ECT2-WT group was increased(P<0.05). Conclusion: miR-302b-3p can inhibit the proliferation and induce the apoptosis of EC-109 cells,and its mechanism may be related to the targeting regulation of ECT2 protein expression.

Key words: miR-302b-3p, esophageal neoplasms, cell proliferation, apoptosis, epithelial cell transformation sequence 2 gene