circCEP70 encoded protein inhibits the progression of hepatocellular carcinoma.

Cirrhosis is closely related to hepatocellular carcinoma (HCC), however, the regulation of circular RNA (circRNA) in HCC with cirrhotic background has not yet been well illustrated. In this study, high throughput circRNA sequencing was applied to identified candidate circRNAs in HCC samples with cirrhotic background. The biological function of candidate circRNA was validated in both in vitro and in vivo settings. Additionally, Alphafold 3, mass spectrometry analysis and immunofluorescence were employed to investigate the underlying mechanisms involved. We found circCEP70 exhibited significantly higher expression levels in cirrhotic HCC samples and showed a positive correlation with improved prognosis. The RNA binding protein U2AF2 was found to suppress the expression of circCEP70 in cirrhosis patients. In vitro and in vivo experiments, including CCK-8, EdU, plate cloning, transwell, scratch, subcutaneous tumor formation, liver metastasis in situ, and lung metastasis assays confirmed the anti-carcinogenic effects. Mechanistically, circCEP70 encoded a novel protein named CEP70-160aa, which interacted with PKM2 and hindered its translocation into the nucleus. This interaction led to reduce STAT3 phosphorylation in the nucleus, thus inhibiting HCC proliferation and metastasis. In cirrhotic microenvironment, circCEP70 prevented HCC proliferation and metastasis through PKM2/STAT3 axis, and RNA binding protein U2AF2 could inhibit circCEP70 expression.