Mir-25 Promotes Metastasis of Esophageal Cancer by Targeting BTG2

At present times, various kinds of literature have suggested the miR-25 acts as an oncogene in various types of human malignancies and until now, very less work has been performed pertaining to the role of miR-25 in esopharyngeal cancer. This study was performed to confirm that miR-25 is overexpressed in esophageal squamous cell carcinoma (ESCC) tumor tissue as a prognostic biomarker and to clarify the mechanism of miR-25. The expression levels of miR-25 and BTG2 were detected in esophageal squamous cell carcinoma tumor tissue. A stably knocked-down miR-25 cell line (miR-25KD) was established in esophageal squamous cell carcinoma cell lines. Moreover, a CCK-8 assay was performed for determining the role of miR-25 in proliferation. The Transwell assays were organized to detect metastasis. Later, a gene profiling study was carried out to identify the gene expression pertaining to tumor progression. The expression of miR-25 in the esophageal cancer tissues was much higher compared with that in paracarcinoma tissues (6.42 +/- 4.28 VS 3.36 +/- 2.63, p<0.001). A high level of miR-25 was identified to be correlated with postoperative metastasis (chi(2)=8.187, p =0.004). BTG2 levels were significantly lower in tumor tissues (3.24 +/- 2.79) than those in adjacent non-tumor tissues (1.96 +/- 1.56 VS 2.64 +/- 1.41, p<0.001). Negative signs of BTG2 were also associated with postoperative metastasis (chi(2)=7.766, p=0.005). Besides, BTG2-negative cancer tissues are often accompanied by increased miR-25 expression levels (chi(2)=18.379, p<0.001). Patients with high miR-25 levels were found with worse overall survival (OS) (chi(2)=6.906, p=0.009) and metastasis-free survival (MFS) (chi(2)=4.991, p=0.025). Patients with positive BTG2 had better OS (chi(2)=12.917, p <0.001) and MFS (chi(2)=14.173, p<0.001). Knockdown of miR-25 helped to inhibit the proliferation and metastatic ability of esophageal cancer cells. Also, MiR-25 inhibits the expression of BTG2 directly. Results also show that miR-25 also helps to suppress the expression of vimentin and increase the expressions of E-cadherin and BTG2. MiR-25 promotes ESCC progression by directly inhibiting the expression of BTG2. MiR-25 and BTG2 can be utilized as prognostic biomarkers.