MiR-335 promotes cell proliferation by inhibiting MEF2D and sensitizes cells to 5-Fu treatment in gallbladder carcinoma

OBJECTIVE: Gallbladder carcinoma is a malignant tumor in the bile duct with poor prognosis. Although aberrant expression of miR-335 has been reported in the tumor tissues of gallbladder carcinoma, the biological role of miR-335 was still largely unknown. This study was intended to explore the role of miR-335 in the progression of gallbladder carcinoma. PATIENTS AND METHODS: The gallbladder carcinoma cell lines GBC-SD and SGC-996 were used in our study. MiR-335 mimic, miR-335 inhibitor, and si-myocyte enhancer factor 2D (MEF2D) were transfected into gallbladder carcinoma cells, respectively. (3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay analysis was used to determine cell viability. The colony formation was also analyzed. Cell cycle progression was determined using flow cytometer. To verify the target gene of miR-335, the luciferase assay was used. RESULTS: MiR-335 overexpression inhibited cell viability and colony formation of GBC-SD and SGC-996 cells. The percentage of cells in first gap phase (G1)/resting phase (GO) was significantly increased, and the expression of cell division cycle 2 (cdc2) and cell division cycle 25 (cdc25) was decreased after miR-335 was over-expressed, indicating its role in inducing the cell cycle arrest of GBC-SD and SGC-996 cells. MEF2D was up-regulated in gallbladder cancer and associated with tumor size and clinical stage. Down-regulation of MEF2D inhibited cell viability and colony formation, induced cell cycle arrest in G1/GO phase, and decreased the expression of cdc2 and cdc25 in GBC-SD and SGC-996 cells. Bioinformatics analysis by TargetScan and luciferase assay verified that MEF2D could be targeted by miR-335. Importantly. the effects of miR-335 inhibitor on cell growth were rescued by small interfering RNA of MEF2D (siMEF2D) in GBC-SD and SGC-996 cells. Besides. miR-335 overexpression increased cell sensitivity to 5-Fluoracil (Fu) treatment and decreased the expression levels of ATP-binding cassette transporter B1 (ABCB1) and ATP-binding cassette G2 (ABCG2) in GBC-SD and SGC-996 cells. CONCLUSIONS: MiR-335 participates in the progression of gallbladder carcinoma by targeting MEF2D. MiR-335 may be a potential therapeutic target for gallbladder carcinoma.