Tumor-Derived Exosomal circ_0020095 Promotes Colon Cancer Cell Proliferation and Metastasis by Inhibiting M1 Macrophage Polarization

Tumor-associated macrophages (TAM) have been shown to regulate colon cancer (CC) progression. However, it is not clear whether tumor-derived exosomal circular RNA (circRNA) regulates TAM to influence CC progression. The expression levels of circ_0020095, M1 macrophage markers, M2 macrophage markers, and interleukin-1 receptor-associated kinase 1 (IRAK1) were determined by qRT-PCR. Cell proliferation, migration and invasion were examined by EdU assay, wound healing assay and transwell assay. Exosomes derived from CC cells were used to treat M0 macrophages. M1 macrophage surface marker CD86 was detected by flow cytometry, and protein expression was examined by western blot. Then, the medium of exosome-treated M0 macrophages was used to culture CC cells to determine CC cell functions. RNA pull-down assay, RIP assay and dual-luciferase reporter assay were performed to validate interaction. Circ_0020095 had elevated expression in CC tissues and cells, and its knockdown repressed CC cell proliferation and metastasis. M0 macrophages could take by CC cell-derived exosomes to regulate circ_0020095 expression. Exosomal circ_0020095 restrained M1 macrophage polarization and increased M2 macrophage polarization to enhance CC cell progression. Besides, IRAK1 silencing could promote CC cell proliferation and metastasis by inhibiting M1 macrophage polarization, and its overexpression also abolished the effect of exosomal circ_0020095. Mechanistically, circ_0020095 could competitively bind to IGF2BP1 and then reduced the binding ability of IGF2BP1 and IRAK1 3'UTR. Tumor-derived exosomal circ_0020095 promoted CC cell progression via inhibiting M1 macrophage polarization through IGF2BP1/IRAK1 axis.