Hepatocellular carcinoma (HCC) is a common malignancy. CD8+ T cell-mediated immune response is critical for the inhibition of HCC progression. M2 macrophages participate in HCC progression. This study set out to investigate the effect of M2 macrophage-derived extracellular vesicles (EVs) on CD8+ T cell exhaustion in HCC. M2 macrophage-derived EVs were isolated and identified. The murine model of primary HCC was established through DEN/CCl4 induction, and model mice were injected with EVs. Peripheral blood mononuclear cells (PBMCs) were isolated from the mouse liver and CD8+ T cells were sorted. The expressions of immune checkpoint inhibitory receptors and effector cytokines on CD8+ T cells were detected, followed by the evaluation of CD8+ T cell proliferation and killing function. miR-21-5p expression in M2 macrophage-derived EVs was detected. The binding relationship between miR-21-5p and YOD1 was verified. The activation of the YAP/β-catenin pathway was detected. Consequently, M2 macrophage-derived EVs promoted CD8+ T cell exhaustion in HCC mice. miR-21-5p expression was upregulated in M2 macrophage-derived EVs, and EVs carried miR-21-5p into HCC tissues. miR-21-5p targeted YOD1. Inhibition of miR-21-5p or overexpression of YOD1 annulled the promoting effect of EVs on CD8+ T cell exhaustion. YOD1 inactivated the YAP/β-catenin pathway. In conclusion, M2 macrophage-derived EVs facilitated CD8+ T cell exhaustion via the miR-21-5p/YOD1/YAP/β-catenin axis. This study may confer novel insights into the immunotherapy of HCC.

As an epitranscriptomic modulation manner, N6‐methyladenosine (m6A) modification plays important roles in various diseases, including hepatocellular carcinoma (HCC). m6A modification affects the fate of RNAs. The potential contributions of m6A to the functions of RNA still need further investigation. In this study, we identified long noncoding RNA FAM111A‐DT as an m6A‐modified RNA and confirmed three m6A sites on FAM111A‐DT. The m6A modification level of FAM111A‐DT was increased in HCC tissues and cell lines, and increased m6A level was correlated with poor survival of HCC patients. m6A modification increased the stability of FAM111A‐DT transcript, whose expression level showed similar clinical relevance to that of the m6A level of FAM111A‐DT. Functional assays found that only m6A‐modified FAM111A‐DT promoted HCC cellular proliferation, DNA replication, and HCC tumor growth. Mutation of m6A sites on FAM111A‐DT abolished the roles of FAM111A‐DT. Mechanistic investigations found that m6A‐modified FAM111A‐DT bound to FAM111A promoter and also interacted with m6A reader YTHDC1, which further bound and recruited histone demethylase KDM3B to FAM111A promoter, leading to the reduction of the repressive histone mark H3K9me2 and transcriptional activation of FAM111A. The expression of FAM111A was positively correlated with the m6A level of FAM111A‐DT, and the expression of methyltransferase complex, YTHDC1, and KDM3B in HCC tissues. Depletion of FAM111A largely attenuated the roles of m6A‐modified FAM111A‐DT in HCC. In summary, the m6A‐modified FAM111A‐DT/YTHDC1/KDM3B/FAM111A regulatory axis promoted HCC growth and represented a candidate therapeutic target for HCC.

Background Macrophages are the major components of tumour microenvironment, which play critical roles in tumour development. Long noncoding RNAs (lncRNAs) also contribute to tumour progression. However, the potential roles of lncRNAs in modulating the interaction between cancer cells and macrophages in hepatocellular carcinoma (HCC) are poorly understood. Methods The expression of lncRNA ZNNT1 in tissues and cells was measured using qRT-PCR. The roles of ZNNT1 in HCC cells and macrophages were investigated using in vitro and in vivo assays. The molecular mechanisms of ZNNT1 were explored using qRT-PCR, RNA immunoprecipitation, RNA pull-down, chromatin immunoprecipitation, enzyme linked immunosorbent assay, and dual-luciferase reporter assays. Results ZNNT1 was identified as an HCC-related lncRNA, which was upregulated and associated with poor prognosis of HCC. ZNNT1 promoted HCC cellular growth, migration, and invasion, and suppressed apoptosis in vitro. ZNNT1 promoted HCC xenograft growth in vivo. Furthermore, ZNNT1 recruited and induced M2 polarization of macrophages. Mechanistically, ZNNT1 upregulated SPP1 expression and osteopontin (OPN) secretion via sponging miR-181a/b/c/d-5p and miR-33a/b-5p. Functional rescue assays identified OPN as the mediator of the oncogenic roles of ZNNT1 in HCC cells and also the effects of ZNNT1 on macrophages. M2 Macrophages-recruited by ZNNT1 enhanced malignant phenotypes of HCC cells, which was mediated by S100A9 secreted by M2 macrophages. Intriguing, S100A9 secreted by M2 macrophages also upregulated ZNNT1 expression in HCC cells via AGER/NF-κB signaling. Conclusions ZNNT1, OPN, and S100A9 formed a positive feedback loop, which promoted macrophages recruitment and M2 polarization, and enhanced malignant features of HCC cells. The ZNNT1/OPN/S100A9 feedback loop represents potential therapeutic target for HCC.