Exosome-transmitted circCOG2 promotes colorectal cancer progression via miR-1305/TGF-β2/SMAD3 pathway

Circular RNAs (circRNA) are abundantly present in the exosome. Yet, the role of exosome-transmitted circRNA in colorectal cancer (CRC) remains unclear. In this study, we examined the function and mechanism of circCOG2 in CRC. We analyzed the expression of circCOG2 in CRC tissues, plasmas, and exosomes by qRT-PCR. The function of circCOG2 was evaluated by CCK-8, clone formation, transwell and wound healing assay, and using an in vivo study; while its mechanism was analyzed using a dual luciferase reporter assay, RNA pull-down assay, Western blot, and rescue experiments. We found that circCOG2 was increased in CRC tissues, plasmas, and exosomes. Upregulated circCOG2 promoted CRC proliferation, migration, and invasion through the miR-1305/TGF-β2/SMAD3 pathway, and this effect could be transmitted from CRC cells with the high metastatic potential to CRC cells with low metastatic potential by exosomes. Our results revealed that circCOG2 is correlated with poor prognosis and may be used as a therapeutic target for CRC.