Abstract:Objective To explore the effects of circBIRC6 on the proliferation, cell cycle and apoptosis of gastric cancer cells and its possible mechanism. Methods The specimens of cancer tissues and para-cancerous tissue were collected in 53 patients with gastric cancer treated in Xiaogan Central Hospital Affiliated to Wuhan University of Science and Technology from January 2020 to May 2020. RT-qPCR was used to detect the expression of circBIRC6 and miR-449b-5p in gastric cancer tissues, para-cancerous tissues, human gastric mucosal epithelial cells GES1, and human gastric cancer cells lines (SNU-1, AGS and HS-746T). SNU-1 cells were taken as the research objects and were divided into si-NC group, si-circBIRC6 group, miR-NC group, miR-449b-5p group, si-circBIRC6+anti-miR-NC group and si-circBIRC6+anti-miR-449b-5p group. Proliferation, cell cycle and apoptosis of SNU-1 cells were detected by cell counting kit-8 (CCK-8) and flow cytometry assays, respectively. The dual luciferase reporter experiment was conducted to detect the effect of miR-449b-5p overexpression on luciferase activity of wild-type vector WT-circBIRC6. Western blot was used to detect the expression of cleaved caspase-3 protein. Results Compared with para-cancerous tissues, the expression of circBIRC6 in gastric cancer tissues was increased significantly(P＜0.05), while the expression of miR-449b-5p was decreased (P＜0.05). Compared with GES1 cells, the expressions of circBIRC6 in SNU-1, AGS, and HS-746T cells significantly increased (P<0.05), and the expression of miR-449b-5p decreased (P<0.05). Compared with those in si-NC group, the cell viability and the proportion of S-phase cells were decreased (P＜0.05), while the proportion of cells in the G0/G1 phase, the rate of apoptosis and the protein level of cleaved caspase-3 were increased in si-circBIRC6 group (P＜0.05). Compared with those in miR-NC group, the cell viability and the S-phase cell ratio decreased (P＜0.05), and the G0/G1 phase cell ratio, cell apoptosis rate and the protein level of cleaved caspase-3 significantly increased in miR-449b-5p group (P<0.05). Overexpression of miR-449b-5p significantly reduced the luciferase activity of WT-circBIRC6 (P<0.05). Compared with those in si-circBIRC6+anti-miR-NC group, the cell viability and the S-phase cell ratio were increased (P＜0.05), while G0/G1 phase cell ratio, cell apoptosis rate and protein level of cleaved caspase-3 were decreased in si-circBIRC6+anti-miR-449b-5p group (P<0.05).Conclusions Interfering with the expression of circBIRC6 could inhibit the proliferation and cell cycle progression and induce apoptosis of gastric cancer cells by up-regulating the expression of miR-449b-5p.