EIF4A3-Mediated circ_0008126 Inhibits the Progression and Metastasis of Gastric Cancer by Modulating the APC/β-Catenin Pathway.

Background: Mounting evidence exhibits circRNAs as critical regulators in the progression of many tumors. The regulatory function and potential mechanism by which circ_0008126 in gastric cancer (GC) is unknown.

Methods: To validate and analyze the expression levels and clinical values of circ_0008126 in GC patients, the biological phenotypes of circ_0008126 in GC were investigated in vitro and in vivo. The roles and effects of circ_0008126 on miR-502-5p, EIF4A3, and APC in GC cells were explored using rescue experiment, RNA stability assay, RNA pull-down, dual-luciferase reporter, RNA immunoprecipitation (RIP), RNA FISH, immunofluorescence (IF), and TOP/Flash and FOP/Flash assays.

Results: Circ_0008126 expression levels were prominently down-regulated in GC tissues and cells. Importantly, low expression of circ_0008126 was relevant to the more lymphatic metastasis, advanced TNM stage, and poor survival period in patients with GC. Functionally, circ_0008126 inhibited GC cell proliferative activity, metastatic ability, and epithelial-mesenchymal transition (EMT) in vitro and vivo. Mechanistically, we verified that EIF4A3 can mediate the formation of circ_0008126, and circ_0008126 could competitively bind miR-502-5p and alleviate its role and effect on APC, thus inactivating the β-catenin pathway in GC. Additionally, circ_0008126 was determined to increase the stability of APC mRNA by interacting with cytoplasmic EIF4A3 protein and then enhancing the APC expression.

Conclusions: These data demonstrate that EIF4A3-mediated circ_0008126 could regulate the APC expression and inactivate the β-catenin pathway partly by binding to miR-502-5p and EIF4A3, thus inhibiting the tumorigenesis and development of GC.