CircSMEK1 Suppresses HCC via the hnRNPK-IGF2-AKT Axis: A Diagnostic Biomarker and Therapeutic Target.

The mechanism underlying metabolic dysfunction-associated steatohepatitis (MASH) to hepatocellular carcinoma (HCC) is elusive, and whether circRNA can serve as biomarker or therapeutic target for MASH/HCC needs to be systematically explored. Integrative transcriptomic analysis of circRNA from MASH and HCC were performed. Multi-cohort analyses of serum and tissues from MASH and HCC patients (n = 206) were conducted. Mechanisms are explored via RNA-protein interaction assays, CRISPR-mediated knockdown, and xenograft/PiggyBac-mediated mice models. circSMEK1 is significantly decreased in MASH/HCC tissues and serum, correlating with tumor size, vascular invasion, and overall survival. Mechanistically, nuclear circSMEK1 binds hnRNPK, promoting its ubiquitin-mediated degradation, suppressing IGF2 transcription and PI3K/AKT signaling. Loss of circSMEK1 elevated autocrine IGF2 in HCC promoting tumor growth, also activated AKT in cancer-associated fibroblasts through paracrine, fostering an immunosuppressive microenvironment. SF3B4 overexpression drove circSMEK1 depletion in HCC. In murine models, circSMEK1 restoration inhibited tumor growth and metastasis. circSMEK1 is a tumor-suppressor in MASH/HCC through the hnRNPK-IGF2-AKT axis. The serum level of circSMEK1 has non-invasive diagnostic value for HCC (AUC = 0.790), as well as potential diagnostic utility for early HCC or high-risk MASH, owing to its key role in bridging MASH to HCC progression. Restoring of circSMEK1, alone or combined with IGF2 inhibitors, proposing a novel therapeutic strategy for HCC.