Platycodon grandiflorum-derived extracellular vesicles suppress triple-negative breast cancer growth by reversing the immunosuppressive tumor microenvironment and modulating the gut microbiota

Despite the approval of several artificial nanotherapeutics for the treatment of triple-negative breast cancer (TNBC), significant challenges, including unsatisfactory therapeutic outcomes, severe side effects, and the high cost of large-scale production, still restrict their long-term application. In contrast, plant-derived extracellular vesicles (PEVs) exhibit promising potential in cancer therapy due to their negligible systemic toxicity, high bioavailability and cost- effectiveness. In this study, we developed an alternative strategy to inhibit TNBC via Platycodon grandiflorum (PG)-derived extracellular vesicles (PGEVs). The PGEVs were isolated by ultracentrifugation and sucrose gradient centrifugation method and contained adequate functional components such as proteins, lipids, RNAs and active molecules. PGEVs exhibited remarkable stability, tolerating acidic digestion and undergoing minimal changes in simulated gastrointestinal fluid. They were efficiently taken up by tumor cells and induced increased production of reactive oxygen species (ROS), leading to tumor cell proliferation inhibition and apoptosis, particularly in the TNBC cell line 4T1. Additionally, PGEVs facilitated the polarization of tumor-associated macrophages (TAMs) toward M1 phenotype and increased the secretion of pro-inflammatory cytokines. Further in vivo investigations revealed that PGEVs efficiently accumulated in 4T1 tumors and exerted significant therapeutic effects through boosting systemic anti-tumor immune responses and modulating the gut microbiota whether administered orally or intravenously (i.v.). In conclusion, these findings highlight PGEVs as a promising natural, biocompatible and efficient nanotherapeutic candidate for treating TNBC.