Circular noncoding RNA circ_0007334 sequestrates miR-577 to derepress KLF12 and accelerate colorectal cancer progression.

Colorectal cancer (CRC) is a prevalent malignant tumor with a poor prognosis. Circular RNA (circRNA) circ_0007334 is related to cell proliferation in CRC. This study is designed to explore the role and mechanism of circ_0007334 in CRC progression. Circ_0007334, microRNA-577 (miR-577) and kruppel-like factor 12 (KLF12) levels were measured by real-time quantitative PCR (RT-qPCR). Exosomes were detected by a transmission electron microscope and nanoparticle tracking analysis (NTA). CD63, TSG101, matrix metallopeptidase-2 (MMP-2), MMP-9, VEGFA and KLF12 protein levels were examined by western blot assay. The binding relationship between miR-577 and circ_0007334 or KLF12 was predicted by circRNA interactome or Starbase and verified by a dual-luciferase reporter and RNA immunoprecipitation (RIP) assays. Cell viability, colony number, migration, invasion and angiogenesis were detected by cell counting kit-8 (CCK-8), colony formation, wound healing, transwell and tube formation assays. The biological role of circ_0007334 was examined by the xenograft tumor model in vivo. Circ_0007334 and KLF12 were increased, and miR-577 was decreased in CRC tissues and cells. Also, circ_0007334 expression was upregulated in CRC cell-derived exosomes. Circ_0007334 deficiency repressed cell viability, colony formation, migration, invasion, and angiogenesis in CRC cells. Mechanically, circ_0007334 could regulate KLF12 expression by sponging miR-577. Circ_0007334 downregulation or exosomal circ_0007334 silencing blocked CRC tumor growth in vivo. These results presented that circ_0007334 deficiency exerts a tumor-suppressor by the miR-577/KLF12 axis in CRC, and indicated that exosomal circ_0007334 could hinder CRC tumor growth and angiogenesis in vivo. Our findings provided a novel therapeutic strategy for CRC.