Circ_0005615 Regulates the Progression of Colorectal Cancer Through the miR-873-5p/FOSL2 Signaling Pathway

To determine the effects of circ_0005615 in CRC development and underneath mechanism. The expression levels of circ_0005615, microRNA-873-5p (miR-873-5p) and FOS-like antigen 2 (FOSL2) mRNA were determined by quantitative real-time polymerase chain reaction (qRT-PCR). The protein levels of exosome makers, proliferation-related makers and FOSL2 were detected by western blot or immunohistochemistry assay. Cell proliferation was evaluated by cell counting kit-8 (CCK-8) and cell colony formation assays. Cell migration and invasion were demonstrated by a transwell assay. Cell apoptosis was investigated by flow cytometry analysis. The binding relationship between miR-873-5p and circ_0005615 or FOSL2 was predicted by circular RNA interactome and targetscan online databases, respectively, and identified by dual-luciferase reporter assay. The impacts of circ_0005615 silencing on tumor formation were determined by in vivo tumor formation assay. Circ_0005615 expression was dramatically upregulated in serum exosomes of CRC patients compared with the control group. The CRC patients with a high circ_0005615 expression had a poor survival rate. Circ_0005615 and FOSL2 expressions were apparently increased, while miR-873-5p was decreased in CRC tissues or cells relative to control groups. Circ_0005615 knockdown inhibited cell proliferation, migration, and invasion, whereas promoted cell apoptosis in CRC; however, miR-873-5p inhibitor attenuated these impacts. Additionally, circ_0005615 acted as a sponge of miR-873-5p and miR-873-5p bound to FOSL2. FOSL2 overexpression restrained the effects of miR-873-5p mimic on CRC progression. Furthermore, circ_0005615 knockdown suppressed tumor growth in vivo. Circ_0005615 modulated CRC malignant progression by controlling FOSL2 expression through sponging miR-873-5p. This finding lays a foundation for the study on circRNA-mediated CRC therapy.