Circ_0071589 contributes to growth, angiogenesis, and metastasis of colorectal cancer through regulating miR‐296‐5p/EN2 axis

To explore the function and regulation mechanism of circ_0071589 in colorectal cancer (CRC). The expression levels of circ_0071589, microRNA-296-5p (miR-296-5p), and Engrailed-2 (EN2) were detected by quantitative real-time polymerase chain reaction (qRT-PCR). Western blot was performed to check the protein levels of EN2 and apoptosis-related proteins. Cell colony formation and 5-Ethynyl-29-deoxyuridine (EdU) assay were used to exhibit cell proliferation. Cell apoptosis was shown by flow cytometry. Tube formation assay manifested the angiogenesis ability of CRC cells. Transwell assay demonstrated cell migration and invasion. The interaction between miR-296-5p and circ_0071589 or EN2 was identified by dual-luciferase reporter assay. The effect of circ_0071589 on tumor formation was demonstrated by in vivo tumor formation experiments. Immunohistochemical (IHC) assay was used to detect the positive cell rate of Ki67 in tumor tissue. Circ_0071589 was upregulated in CRC tissue and cells. Circ_0071589 knockdown repressed CRC cells proliferation, angiogenesis, migration, invasion, and promoted cell apoptosis. MiR-296-5p was downregulated in CRC tissue and cells. And miR-296-5p inhibitor could reverse the malignant phenotypes and angiogenesis inhibition of CRC cells caused by circ_0071589 knockdown. Additionally, miR-296-5p decreased CRC cell colony formation, EdU-positive cells, angiogenesis, and increased cell apoptosis through reducing the expression level of EN2. Finally, circ_0071589 silencing inhibited tumor formation in vivo. Circ_0071589 upregulated EN2 expression through sponging miR-296-5p, thereby promoting the malignant phenotype and angiogenesis of CRC cells, which provided a new target for the treatment of CRC.