Exosomal miR-451a Functions as a Tumor Suppressor in Hepatocellular Carcinoma by Targeting LPIN1.

BACKGROUND/AIMS: Emerging evidence suggests that exosomal microRNAs (miRNAs) mediate hepatoma progression through the post-translational regulation of their targets. However, characteristically-expressed miRNAs and their functions in the tumor and tumor-associated angiogenesis remain poorly understood.

METHODS

miRNA sequencing (HiSeq 2500 SE50) was performed to identify miRNA species that are involved in the hepatocellular carcinoma (HCC) pathogenesis. We identified miR-451a downregulation according to its expression and TCGA analysis. miR-451a was found to be mainly involved in cell viability, apoptosis, cell cycle and migration both in HCC and endothelial cell lines. LPIN1 was predicted to be a target of this miRNA based on TargetScan, GSEA analysis, and the Uniprot database. We performed real time PCR and dual luciferase assays to confirm these results.

RESULTS

We identified that miR-451a is significantly downregulated in serum-derived exosomes from HCC patients, as compared to expression in those from normal individuals. We further confirmed that overexpression of miR-451a functions in HCC and endothelia cells in vitro and in vivo. Exosomal miR-451a, as a tumor suppressor, was found to induce apoptosis both in HCC cell lines and human umbilical vein endothelial cells (HUVECs). In addition, miR-451a suppressed HUVEC migration, tube formation, and vascular permeability. Importantly, we demonstrated that LPIN1 is a critical target of miR-451a, and promotes apoptosis in both HCC and endothelial cells.

CONCLUSION

Our study provides the novel finding that exosomal miR-451a targets LPIN1 to inhibit hepatocellular tumorigenesis by regulating tumor cell apoptosis and angiogenesis. These results have clinical implications regarding the deregulation of miRNAs in HCC.