A novel circular RNA circ-ZNF652 promotes hepatocellular carcinoma metastasis through inducing snail-mediated epithelial-mesenchymal transition by sponging miR-203/miR-502-5p.

Circular RNA (circRNA), a special class of non-coding RNA, is increasingly being realized as a critical regulator in human diseases, including carcinomas. However, its role in hepatocellular carcinoma (HCC) metastasis remains largely unknown. Herein, we enrolled three Gene Expression Omnibus (GEO) databases and screened and identified a novel circRNA, circ-ZNF652 (hsa_circ_0003258), which was significantly upregulated in HCC tissues and cell lines. Importantly, HCC patients with high circ-ZNF652 expression were more prone to vascular invasion, intrahepatic metastasis, distant metastasis, and poor outcome. Subsequent functional experiments showed that depletion of circ-ZNF652 dramatically suppressed the migratory and invasive capabilities of HCC cells in vitro as well as tumor metastasis in vivo by inhibiting the process of epithelial-mesenchymal transition (EMT). Mechanistically, circ-ZNF652 could physically interact with miR-203 and miR-502-5p to increase the expression of their common target gene Snail (a key transcription factor that triggers EMT), thereby promoting the metastasis of HCC. In turn, the upregulated Snail was capable of binding to the E-box motif (CAGGTG) on the promoter of circ-ZNF652 to elevate circ-ZNF652 expression. Collectively, our findings suggest that circ-ZNF652 is a novel driver of EMT and unveil the important regulatory role of circ-ZNF652/miR-203/miR-502-5p/Snail feedback loop in HCC metastasis.