Inhibiting circ_0000673 blocks the progression of colorectal cancer through downregulating CPSF6 via targeting miR-548b-3p.

Background: Colorectal cancer (CRC) is one of the most common cancers, and its progression is regulated by several factors, including circular RNA (circRNA).

Objectives: The objective of this study was to determine the role, or roles, of circ_0000673 in CRC.

Material and methods: We used quantitative real-time polymerase chain reaction (qPCR) to detect the expression of circ_0000673, miR-548b-3p and cleavage and polyadenylation specific factor 6 (CPSF6) in DLD-1 and RKO cells. Cell Counting Kit-8 (CCK-8) and 5-ethynyl-2'-deoxyuridine (EdU) assays were used to determine circ_0000673 roles in proliferation. Wound healing and transwell assays were used to detect cell migration and invasion abilities. Expression of CPSF6 protein and stem cell-associated proteins were examined using western blot. The putative relationship between miR-548b-3p and circ_0000673 or CPSF6 was verified with dual-luciferase reporter assay. The role of circ_0000673 in CRC was also investigated in a tumor xenograft assay in nude mice.

Results: Circ_0000673 expression was increased in CRC tissues and cancer cells. Silencing circ_0000673 reduced tumor cell proliferation, migration and invasion, while also decreasing cell stemness. MiR-548b-3p was found to be a target of circ_0000673, while CPSF6 was a downstream target of miR-548b-3p. The tumor-regulatory effects of si-circ_0000673, anti-miR-548b-3p and oe-CPSF6 were partially reversed by anti-miR-548b-3p, si-CPSF6 and si-circ_0000673, respectively, in rescue assays. Downregulation of circ_0000673 reduced solid tumor growth in vivo.

Conclusions: Circ_0000673 inhibition reduced CPSF6 expression by targeting miR-548b-3p, thereby blocking proliferation, migration and invasion of CRC tumor cells.