Hypoxic tumour‐derived exosomal <scp>miR</scp>‐1290 exacerbates the suppression of <scp>CD8</scp>+ T cells by promoting <scp>M2</scp> macrophage polarization

Hypoxia plays an important role in the metastasis of hepatocellular carcinoma (HCC). Exosomes have been widely studied as mediators of communication between tumours and immune cells. However, the specific mechanism by which hypoxic HCC cell-derived exosomes suppress antitumor immunity is unclear. Hypoxia scores were determined for The Cancer Genome-Liver Hepatocellular Carcinoma (TCGA-LIHC) dataset patients, and HCC patients in the hyperhypoxic group had a higher degree of M2 macrophage infiltration. Patients in the M2 high-invasion group had a lower probability of survival than those in the low-invasion group. In vivo and in vitro experiments demonstrated that exosomes secreted by hypoxic HCC cells promote M2 macrophage polarization. This polarization induces apoptosis in CD8+ T cells. Additionally, it encourages epithelial-mesenchymal transition (EMT), which increases HCC migration. Exosomal miRNA sequencing revealed that miR-1290 was highly expressed in exosomes secreted by hypoxic HCC cells. Mechanistically, miR-1290 in macrophages inhibited Akt2 while upregulating PD-L1 to promote M2 polarization, induce apoptosis in CD8⁺ T cells, and enhance EMT in HCC. Animal studies found that the miR-1290 antagomir in combination with the immune checkpoint inhibitor produced better antitumor effects than the monotherapies. In conclusion, the secretion of exosome-derived miR-1290 from HCC cells in a hypoxic environment supported immune escape by HCC cells by promoting M2 macrophage polarization to induce apoptosis in CD8⁺ T cells and enhance EMT that promoted HCC metastasis. Therefore, miR-1290 is an important molecule in antitumor immunity in HCC, and inhibition of miR-1290 could provide a novel immunotherapeutic approach for HCC treatment.