Background & aims: Chronic hepatitis B virus (HBV) carriers have a high risk to develop hepatocellular carcinoma (HCC) but the underlying mechanism remains unclear. Recent studies suggest that viral-human hybrid RNA transcripts, which play a critical role in promoting HCC progression, may be the molecules responsible for the development of HCC in HBV infected patients. Here we determine whether HBx-LINE1, a hybrid RNA transcript of the human LINE1 and the HBV-encoded X gene generated in tumor cells of HBV-positive HCC, can serve as a molecular sponge for sequestering miR-122 and promoting liver cell abnormal mitosis and mouse hepatic injury.
Methods: Paired tumor and distal normal liver tissue specimens, as well as HBx-LINE1 overexpressing hepatic cells, were used to test the relationship between HBx-LINE1 and miR-122. Levels of HBx-LINE1 and miR-122 were assayed by qRT-PCR and Northern blot. HBx-LINE1-miR-122 binding was analyzed by luciferase reporter assay. Mouse hepatic injury was monitored by tissue staining and serum aspartate transaminase, alanine aminotransferase and total bilirubin measurement.
Results: HBx-LINE1 in HBV-positive HCC tissues was inversely correlated with miR-122. Each HBx-LINE1 consists of six miR-122-binding sites, and forced expression of HBx-LINE1 effectively depleted cellular miR-122, promoting hepatic cell epithelial-mesenchymal transition (EMT)-like changes, including β-catenin signaling activation, E-cadherin reduction and cell migration enhancement. Mice administered with HBx-LINE1 display a significant mouse liver cell abnormal mitosis and hepatic injury. However, all these effects of HBx-LINE1 are completely abolished by miR-122.
Conclusions: Our finding illustrates a previously uncharacterized miR-122-sequestering mechanism by which HBx-LINE1 promotes hepatic cell EMT-like changes and mouse liver injury.
Keywords: HBV; HBx-LINE1; HCC; miR-122; miRNA sponge.
Copyright © 2015 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved.