Ginseng-Derived Exosomes Attenuate Immune Evasion in NSCLC via PD-L1 Modulation

Background: Non-small cell lung cancer (NSCLC) is a major cause of cancer-related death worldwide. While PD-1/PD-L1 immune checkpoint blockade has shown promise, its efficacy is often limited by tumor-induced immune evasion. Ginseng-derived exosomes (G-Exos), as natural plant-based nanocarriers, may offer a novel strategy for immunomodulation. This study investigated the potential of G-Exos to regulate PD-L1 expression and enhance anti-tumor immunity in NSCLC. Methods: Exosomes were isolated from ginseng cell cultures and characterized via transmission electron microscopy and nanoparticle tracking analysis. Uptake by NSCLC cells was confirmed using PKH26 labeling. In vitro, NSCLC cells were co-cultured with activated T cells to evaluate cytotoxicity (colony formation), cytokine secretion [enzyme-linked immunosorbent assay (ELISA)], and T-cell activation (flow cytometry). PD-L1 expression was assessed by quantitative polymerase chain reaction (qPCR) and Western blot. In vivo, C57BL/6 mice (n = 20) bearing Lewis lung carcinoma (LLC) tumors were randomized into four groups (n = 5/group): PBS, G-Exos (10 μg), anti-PD-L1 (8 μg), or combination therapy. Treatments were administered intravenously every other day for 20 days. Tumor growth was measured, and tissues were analyzed by immunohistochemistry and flow cytometry. Results: G-Exos were efficiently internalized by NSCLC cells and demonstrated immunostimulatory properties in vitro. They enhanced T-cell-mediated cytotoxicity, as reflected by reduced tumor colony formation, and promoted immune activation, evidenced by increased IL-2 and IFN-γ secretion and a higher proportion of CD8⁺ T cells expressing TNF-α and perforin. Mechanistically, G-Exos downregulated PD-L1 expression at both transcriptional and translational levels in NSCLC cells. In vivo, G-Exos treatment significantly inhibited tumor growth and, when combined with anti-PD-L1 monoclonal antibody, exhibited a synergistic effect characterized by greater tumor suppression and increased infiltration of cytotoxic CD8⁺ T cells in the tumor microenvironment. Conclusion: Ginseng-derived exosomes downregulate PD-L1 and enhance T-cell function, counteracting immune evasion in NSCLC. Their synergy with anti-PD-L1 therapy supports their potential as adjuvant nanotherapeutics in cancer immunotherapy.