A SOX9‐AS1/miR‐5590‐3p/SOX9 positive feedback loop drives tumor growth and metastasis in hepatocellular carcinoma through the Wnt/β‐catenin pathway

Hepatocellular carcinoma (HCC) is a prevalent solid tumor with a high global death rate. SRY box 9 (SOX9) has been reported as an oncogene in HCC by several studies, but the underlying mechanism remains largely unexplored. Here, we confirmed upregulation of SOX9 in HCC tissues and cell lines and validated that SOX9 facilitates proliferation, migration and invasion in HCC. We subsequently identified that the long non‐coding RNA (lncRNA) SOX9 antisense RNA 1 (SOX9‐AS1) is a neighbor gene to SOX9; SOX9‐AS1 is also upregulated in HCC, and its expression is positively correlated with that of SOX9. In addition, SOX9‐AS1 appears to have prognostic significance in HCC patients. We showed that SOX9‐AS1 aggravates HCC progression and metastasis in vitro and in vivo. We demonstrated that SOX9‐AS1 sponges miR‐5590‐3p to elevate SOX9 expression, and that SOX9 in turn transcriptionally activates SOX9‐AS1. Moreover, we verified that SOX9‐AS1 regulates SOX9 and its known downstream Wnt/β‐catenin pathway so as to facilitate epithelial‐to‐mesenchymal transition. The results of our rescue assays suggest that SOX9‐AS1 regulates HCC progression through SOX9 and the Wnt/β‐catenin pathway. In conclusion, our study demonstrates that a SOX9‐AS1/miR‐5590‐3p/SOX9 positive feedback loop drives tumor growth and metastasis in HCC through the Wnt/β‐catenin pathway, suggesting SOX9‐AS1 as a novel potential prognostic and treatment target for HCC.