Abstract
OBJECTIVE: The current treatment for hepatocellular carcinoma (HCC) to block angiogenesis and immunosuppression provides some benefits only for a subset of patients with HCC, thus optimised therapeutic regimens are unmet needs, which require a thorough understanding of the underlying mechanisms by which tumour cells orchestrate an inflamed tumour microenvironment with significant myeloid cell infiltration. MicroRNA-223 (miR-223) is highly expressed in myeloid cells but its role in regulating tumour microenvironment remains unknown. DESIGN: Wild-type and miR-223 knockout mice were subjected to two mouse models of inflammation-associated HCC induced by injection of diethylnitrosamine (DEN) or orthotopic HCC cell implantation in chronic carbon tetrachloride (CCl(4))-treated mice. RESULTS: Genetic deletion of miR-223 markedly exacerbated tumourigenesis in inflammation-associated HCC. Compared with wild-type mice, miR-223 knockout mice had more infiltrated programmed cell death 1 (PD-1(+)) T cells and programmed cell death ligand 1 (PD-L1(+)) macrophages after DEN+CCl(4) administration. Bioinformatic analyses of RNA sequencing data revealed a strong correlation between miR-223 levels and tumour hypoxia, a condition that is well-documented to regulate PD-1/PD-L1. In vivo and in vitro mechanistic studies demonstrated that miR-223 did not directly target PD-1 and PD-L1 in immune cells rather than indirectly downregulated them by modulating tumour microenvironment via the suppression of hypoxia-inducible factor 1α-driven CD39/CD73-adenosine pathway in HCC. Moreover, gene delivery of miR-223 via adenovirus inhibited angiogenesis and hypoxia-mediated PD-1/PD-L1 activation in both HCC models, thereby hindering HCC progression. CONCLUSION: The miR-223 plays a critical role in modulating hypoxia-induced tumour immunosuppression and angiogenesis, which may serve as a novel therapeutic target for HCC.