CircRNA hsa_circRNA_0001776 inhibits proliferation and promotes apoptosis in endometrial cancer via downregulating LRIG2 by sponging miR-182

BACKGROUND: Endometrial cancer (EC) is a common malignancy of the female reproductive system. Circular RNAs (circRNAs) were demonstrated to exert critical roles in cancers, including EC. This study aimed to investigate the effects of hsa_circRNA_0001776 (circ_0001776) on EC. METHODS: Real-time quantitative PCR (RT-qPCR) was used to measure circ_0001776, microRNA-182 (miR-182) and leucine-rich repeats and immunoglobulin-like domains 2 (LRIG2) expression. The diagnostic and prognostic values of circ_0001776 were identified by receiver operating characteristic (ROC) curve analysis and survival analysis, respectively. RNase R digestion was used to characterize circ_0001776, and the localization of circ_0001776 was evaluated by cell fractionation assay. Then, cell counting kit-8 (CCK-8), colony formation, and flow cytometry analysis were used to detect cell proliferation and apoptosis, respectively. The real-time glycolytic rate (ECAR) and lactate production were measured by extracellular flux analysis and a lactate assay kit, respectively. Bioinformatics analysis and dual-luciferase reporter assay were used to determine the interaction among circ_0001776, miR-182 and LRIG2. The protein expression of LRIG2 was determined by western blot. Moreover, circ_0001776 overexpression vector was used to upregulate circ_0001776 expression in an animal tumor model. RESULTS: Circ_0001776 and LRIG2 were downregulated, while miR-182 was upregulated in EC tissues and cells. Low expression of circ_0001776 was correlated with the 5-year survival rate of EC patients. Upregulated circ_0001776 markedly attenuated cell proliferation and glycolysis, and enhanced cell apoptosis. Besides, circ_0001776 sponged miR-182 to regulate LRIG2 expression. Circ_0001776 could suppress EC progression by miR-182/LRIG2 axis. Furthermore, we also found that circ_0001776 significantly inhibited tumor growth in vivo. CONCLUSION: Our results confirmed that circ_0001776 inhibited EC tumorigenesis and progression via miR-182/LRIG2 axis, providing a potential therapeutic target for EC.