Long non-coding RNA THOR promotes liver cancer stem cells expansion via β-catenin pathway.

Hepatocellular carcinoma (HCC) is a highly aggressive liver tumor containing cancer stem cells (CSCs), which participate in tumor invasion, therapeutic resistance, and tumor relapse leading to poor outcome and limited therapeutic options. Recently, a novel lncRNA, THOR (testis-associated highly conserved oncogenic long non-coding RNA), was characterized in human cancers and shown to exhibit an oncogenic role. However, the role of THOR in liver cancer stem cells (CSCs) remains obscure. Herein, we observed high expression of THOR in chemoresistant hepatocellular carcinomas (HCCs). A remarkable increase of THOR expression in OV6 or EpCAM-positive liver CSCs as well as in CSC-enriched hepatoma spheres. Interference THOR suppressed liver CSC expansion by inhibiting the dedifferentiation of hepatoma cells and decreasing the self-renewal ability of liver CSCs. Mechanistically, we found β-catenin as the downstream of THOR in HCC cells. The special β-catenin inhibitor FH535 abolished the discrepancy in liver CSC proportion and the self-renewal capacity between THOR knockdown HCC cells and control cells, which further confirmed that β-catenin was required in THOR promoted liver CSCs expansion. Moreover, interference THOR hepatoma cells were more sensitive to sorafenib treatment, indicates that HCC patients with low THOR expression may benefit from sorafenib treatment. Collectively, THOR was upregulated in liver CSCs and could promote HCC cells dedifferentiation and liver CSCs expansion by targeting β-catenin signaling.