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Although circular RNAs (circRNA) are known to modulate tumor initiation and progression, their role in hepatocellular carcinoma (HCC) metastasis remains poorly understood. Here, three metastasis-associated circRNAs identified in a previous circRNA-sequencing study were screened and validated in two HCC cohorts. CircRPN2 was downregulated in highly metastatic HCC cell lines and HCC tissues with metastasis. Patients with HCC with lower circRPN2 levels displayed shorter overall survival and higher rates of cumulative recurrence. Mechanistic studies in vitro and in vivo revealed that circRPN2 binds to enolase 1 (ENO1) and accelerates its degradation to promote glycolytic reprogramming through the AKT/mTOR pathway, thereby inhibiting HCC metastasis. CircRPN2 also acted as a competing endogenous RNA for miR-183–5p, which increases forkhead box protein O1 (FOXO1) expression to suppress glucose metabolism and tumor progression. In clinical samples, circRPN2 expression negatively correlated with ENO1 and positively correlated with FOXO1, and expression of circRPN2, either alone or in combination with ENO1 and FOXO1, was a novel indicator of HCC prognosis. These data support a model wherein circRPN2 inhibits HCC aerobic glycolysis and metastasis via acceleration of ENO1 degradation and regulation of the miR-183–5p/FOXO1 axis, suggesting that circRPN2 represents a possible therapeutic target in HCC. Significance: The circRNA circRPN2 is a potential prognostic biomarker and therapeutic target in hepatocellular carcinoma that suppresses aerobic glycolysis and metastasis.

Expression of heterogeneous nuclear ribonucleoprotein AB (HNRNPAB) has been reported to be dysregulated in tumors, but its specific contributions to tumor formation and progression are not fully understood. Here, we demonstrate that HNRNPAB is overexpressed in highly metastatic cells and tumor tissues from patients with hepatocellular carcinoma (HCC) with recurrence. We found that HNRNPAB overexpression promoted epithelial–mesenchymal transition (EMT) in a manner associated with HCC metastasis in vitro and in vivo. RNA interference-mediated silencing of the EMT factor SNAIL attenuated HNRNPAB-enhanced cell invasion in vitro and lung metastasis in vivo. Mechanistically, HNRNPAB acted to transactivate SNAIL1 transcription, which in turn inhibited transcription of the pivotal SNAIL target gene E-cadherin. Overexpression of HNRNPAB in HCC samples correlated with higher SNAIL levels, shorter overall survival, and higher tumor recurrence. HNRNPAB overexpression, alone or in combination with SNAIL, was found to be a significant independent risk factor for recurrence and survival after curative resection. In conclusion, our findings define HNRNPAB as an activator of EMT and metastasis in HCC that predicts poor clinical outcomes. Cancer Res; 74(10); 2750–62. ©2014 AACR.