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OBJECTIVE To figure out the possible role and mechanism of circ-DB in the pathogenesis of gastric cancer (GCa). PATIENTS AND METHODS 32 cases of postoperative GCa tissue samples and adjacent ones were collected and divided into groups of ≥ 5 cm and < 5 cm according to tumor diameter. Circ-DB, microRNA-34a, and MET expressions were detected by real time-quantitative PCR (RT-qPCR) in GCa tissues and adjacent tissues. To determine the main mode of action of circ-DB, the subcellular localization of circ-DB was examined by dividing the cells into the nucleus and cytoplasmic fractions. The binding of microRNA-34a to circ-DB was demonstrated by a Dual-Luciferase reporter gene assay. The expression of circ-DB in HGC-27 and AGS cells was overexpressed and knocked down to evaluate the migration function of the cells by transwell. The protein expression of MET, as well as the target gene of microRNA-34a, was detected by Western blot. RESULTS The expression of circ-DB and MET in GCa tissues was significantly higher than that in the corresponding adjacent tissues. Circ-DB was positively correlated with MET expression, while microRNA-34a expression was negatively correlated with circ-DB and MET expression. Circ-DB was mainly located in the cytoplasm, and the Dual-Luciferase reporter gene demonstrated that microRNA-34a can bind to circ-DB. The down-regulation of circ-DB expression inhibited the migration of HGC-27 and AGS cells. In vitro cell experiments showed that low expression of circ-DB inhibited cell migration, which could be recovered by the co-transfection with microRNA-34a inhibitor. CONCLUSIONS Circ-DB may regulate MET level through microRNA-34a and affect the proliferative ability and migration of GCa cells.