Exosomal lncRNA HEIH, an essential communicator for hepatocellular carcinoma cells and macrophage M2 polarization through the miR-98-5p/STAT3 axis

Part of human long noncoding RNAs (lncRNAs) has been elucidated to play an essential role in the carcinogenesis and progression of hepatocellular carcinoma (HCC), a type of malignant tumor with poor outcomes. Tumor-derived exosomes harboring lncRNAs have also been implicated as crucial mediators to orchestrate biological functions among neighbor tumor cells. The recruitment of tumor-associated macrophages (TAMs) exerting M2-like phenotype usually indicates the poor prognosis. Yet, the precise involvement of tumor-derived lncRNAs in cross-talk with environmental macrophages has not been fully identified. In this study, we reported the aberrantly overexpressed HCC upregulated EZH2-associated lncRNA (HEIH) in tumor tissues and cell lines was positively correlated with poor prognosis, as well as enriched exosomal HEIH levels in blood plasma and cell supernatants. Besides, HCC cell-derived exosomes transported HEIH into macrophages for triggering macrophage M2 polarization, thereby in turn promoting the proliferation, migration, and invasion of HCC cells. Mechanistically, HEIH acted as a miRNA sponge for miR-98-5p to up-regulate STAT3, which was then further verified in the tumor xenograft models. Collectively, our study provides the evidence for recognizing tumor-derived exosomal lncRNA HEIH as a novel regulatory function through targeting miR-98-5p/STAT3 axis in environmental macrophages, which may shed light on the complicated tumor microenvironment among tumor and immune cells for HCC treatment. Overexpression of lncRNA HEIH in HCC indicates poor prognosis and positively correlates with metastasis. Exosomal lncRNA HEIH promotes macrophage M2 polarization and enhances macrophage-induced tumor progression. lncRNA HEIH serves as a sponge of miR-98-5p to enhance STAT3. Exosomal lncRNA HEIH primes M2 macrophage polarization via targeting miR-98-5p/STAT3 axis.