Hypoxia-induced exosomal lncRNA-PVT1 as a biomarker and mediator of EMT in hepatocellular carcinoma.

OBJECTIVES: Exosomal long noncoding RNAs (lncRNAs) might facilitate epithelial-mesenchymal transition (EMT) in liver cancer after transarterial chemoembolization (TACE), thereby enhancing tumor cell invasiveness and migration. This study investigated the prognostic role of plasma exosomal long noncoding RNA-plasmacytoma variant translocation 1 (lncRNA-PVT1) in TACE treated hepatocellular carcinoma (HCC). METHODS: Plasma exosomal lncRNA-PVT1 was evaluated via qPCR before and after TACE. Hepatoma cell behavior was investigated in different HCC cell lines. A lncRNA-PVT1 plasmid was synthesized and overexpressed, and si-lncRNA PVT1 was transfected into poorly invasive cells to reveal its influence on cell characteristics. The lncRNA-PVT1-FoxM1 interaction was elucidated using a double-luciferase reporter gene assay. The effect of miRNA-345-5p on minimally invasive hepatoma cells was assessed. Three experimental groups were established: poorly invasive cells, poorly invasive cells co-cultured with exosomes from hypoxia-induced highly invasive cells, and poorly invasive cells co-cultured with normal hepatocyte exosomes. Liver cancer cells were subcutaneously inoculated into nude mice, with subsequent observations of weight, tumor formation, and tumor size. RESULTS: We identified two lncRNAs (lncRNA-PVT1 and GAPLINC) associated with EMT in the hypoxic microenvironment of liver cancer. Cox multivariate regression analysis was used to establish a prognostic model distinguishing high- and low-risk groups. Hypoxia-induced HepG2 exosomes significantly promoted EMT in poorly invasive HCC cells. LncRNA-PVT1 overexpression and silencing altered E-cadherin, vimentin, and FoxM1 expression, cell proliferation, invasion, migration, and apoptosis. miR-345-5p directly targeted lncRNA-PVT1 and FoxM1, affecting downstream targets. In vivo, co-culturing poorly invasive hepatoma cells with exosomes from highly invasive cells increased tumor volumes, upregulated lncRNA-PVT1, FoxM1, Ki67, and MMP9 expression, and downregulated miR-345-5p expression. CONCLUSIONS: Plasma exosomal lncRNA-PVT1 expression is upregulated in highly invasive cells post-hypoxia, potentially serving as a biomarker for evaluating liver cancer prognosis after TACE. Through a miRNA-345-5p-mediated competing endogenous RNA mechanism, it promotes EMT in poorly invasive cells, likely contributing to recurrence and metastasis post-HCC interventional embolization.