MicroRNA-449a Inhibits Proliferation and Induces Apoptosis by Directly Repressing E2F3 in Gastric Cancer

Background: MicroRNA-449a is a tumor suppressor that is down-regulated in multiple tumors types. However, the role of miR-449a in gastric cancer (GC) remains largely unknown. Methods: MiR-449a expression was up-regulated using miR-449a mimics, and the role of miR-449a in GC was assessed using cell viability and apoptosis assays. miR-449a target genes were confirmed using luciferase activity, RT-PCR and western blot assays. Results: miR-449a was downregulated in gastric cancer cell lines and gastric cancer tissues. Restoration of miR-449a expression inhibited gastric cancer cell proliferation and colony formation. Significant G0/G1 arrest was observed in gastric cancer cells transfected with miR-449a mimics. Furthermore, combination therapy with miR-449a with cisplatin displayed greater anti-tumor effects than treatment with cisplatin alone. We also identified E2F3 (E2F transcription factor 3), an important transcription factor involved in the proliferation and metastasis of tumor cells, as a direct target gene of miR-449a. Furthermore, silencing E2F3 elicits similar a repressive effect as overexpression of miR-449a in gastric cancer cells, and E2F3 overexpression rescued the repressing effects of miR-449a mimics. Conclusions: This study indicates that the miR-449a/E2F3 axis plays an important role in proliferation and apoptosis in gastric cancer. Therefore, miR-449a represents a novel target for gastric cancer therapy