Hsa_circ_0079557 Promotes the Proliferation of Colorectal Cancer Cells Through the hsa_circ_0079557/miR-502-5p/CCND1 Axis.

Background/aim: Recent studies have demonstrated the crucial regulatory roles of circular RNAs (circRNAs) in cancer initiation and progression. The sponge mechanism of circRNAs has been shown to be widely active in various types of tumors. However, many circRNAs still have not been verified to function through this mechanism. This study aimed to investigate the regulatory mechanism of hsa_circ_0079557 in colorectal cancer (CRC) and its role in CRC progression.

Materials and methods: Raw gene expression profile datasets were downloaded from Gene Expression Omnibus (GEO) and combined to form a new dataset. Hsa_circ_0079557 was found to be highly expressed in CRC. Its role was evaluated in vitro and in vivo through a series of experiments, including quantitative real-time polymerase chain reaction (qRT-PCR), flow cytometry, colony formation, cell counting kit-8 (CCK-8), transwell assays, scratch wound healing assays, nude mice experiments, and immunohistochemistry (IHC). The association between hsa_circ_0079557 and the identified target microRNAs (miRNA) was confirmed through fluorescence in situ hybridization (FISH) and dual-luciferase reporter assays. The downstream target proteins were predicted using the web-based tool "TargetScan," and their expressions were determined using Western blot (WB).

Results: Hsa_circ_0079557 was found to be relatively up-regulated in CRC tissues and cell lines. Suppression of hsa_circ_0079557 expression inhibited cell proliferation in vitro and in vivo. Additionally, hsa_circ_0079557 acted as a "molecular sponge" for miR-502-5p, up-regulating the expression of Cyclin D1 (CCND1).

Conclusion: In this study, we identify a highly expressed circRNA in CRC and propose a novel pathway of hsa_circ_0079557/miR-502-5p/CCND1 in CRC.