Memory-promoting function of miR-379-5p attenuates CD8⁺ T cell exhaustion by targeting immune checkpoints

MicroRNAs (miRNAs) are epigenetic regulators of T cell maturation and exhaustion. However, the mechanisms by which miRNAs influence T cell function in tumor environments remain unclear. This study focuses on miR-379-5p, which counteracts T cell exhaustion and enhances antitumor responses.

Native CD8⁺ T cells were isolated from the blood of healthy donors and subjected to chronic stimulation to induce exhaustion. RNA sequencing and miRNA sequencing were performed to identify differentially expressed miRNAs. These miRNAs underwent bioinformatics analyses, including DESeq enrichment, immune cell infiltration assessment, and patient prognostic outcomes in The Cancer Genome Atlas data sets to assess their potential involvement in T cell exhaustion and antitumor immunity. The biological functions of miRNA on T cell differentiation, cytotoxic killing, and immune checkpoint regulation were investigated using in vitro assays, OT-I B16F10-OVA models, and patient-derived tumor organoids.

MiR-379-5p is downregulated in exhausted T cells and negatively associated with exhausted tumor-infiltrating lymphocytes in advanced tumors. It correlates positively with better survival outcomes in breast cancer, cervical cancer and melanoma. In CD8⁺ T cells, miR-379-5p reduces the expression of immune checkpoint proteins T cell immunoglobulin and mucin-domain containing-3 (TIM3) and T cell immunoreceptor with Ig and ITIM domains (TIGIT) by targeting their 3' untranslated region. Overexpression of miR-379-5p in CD8⁺ T cell promotes differentiation into memory-like T effector cells and enhances cytotoxic killing of cancer cells. The transcription factor nuclear receptor subfamily 4 group A member 1 (NR4A1) with increased expression in exhausted T cells and negatively regulates miR-379, restoring immune checkpoint expression and suppressing cancer-killing ability. In contrast, OT-I T cells expressing ectopic miR-379-5p show increased cytotoxicity against B16F10-OVA tumors in mice. Autologous T cells isolated from patients with breast cancer transduced with miR-379-5p significantly improve killing of tumor organoids derived from the same patients.

MiR-379-5p acts as an epigenetic tumor suppressor by enhancing CD8⁺ T cell effector functions and suppressing T cell exhaustion. MiR-379-5p could represent a novel marker and strategy for cancer immunotherapy, offering promising avenues for enhancing antitumor immune responses.