Objective  To study the biological properties of microRNA(miRNA)-21 expression in esophageal squamous cell carcinoma.  

 Methods  MiRNA-21 sense expression vector, miRNA-21 empty vector and miRNA-21 inhibitor were transfected and detected by fluorescence Real-time PCR. The normal cells of esophageal squamous cell carcinoma TE-1 were used as the control group, and the transfection result  were detected. The cell proliferation activity was detected by cell counting kit-8(CCK-8), and the apoptosis ability was detected by flow cytometry. The invasion ability and migration ability of TE-1 cells were observed by Transwell chamber and scratch test. Changes in the sensitivity of TE-1 cells to radiotherapy were observed by colony formation experiments. The data were analyzed using SPSS 19.0 software.   Results  The result  of Real-time PCR showed that the expression level of miRNA-21 in TE-1 cells was significantly decreased after transfected with miRNA-21 inhibitor (P<0.05). Compared with the normal cell growth group, positive control group and negative control group, the proliferation of TE-1 cells was reduced and apoptosis was accelerated after transfection with miRNA-21 inhibitor (P<0.05). In addition, the ability of cell invasion and migration in the experimental inhibition group was decreased. Clone formation assays showed that inhibition of miRNA-21 expression significantly increased the sensitivity of TE-1 cells to radiation.   Conclusion  Down-regulation of miRNA-21 reduces the proliferation, invasion, migration and sensitivity of radiotherapy in esophageal squamous cell carcinoma TE-1 cells, and is a potential target for the future treatment of esophageal cancer.