Chimeric exosomes-derived immunomodulator restoring lymph node microenvironment for sensitizing TNBC immunotherapy

Immunotherapy is a breakthrough in the treatment of triple-negative breast cancer (TNBC), whereas is effective in a portion of patients. Our clinical studies found that lipid homeostasis imbalance and dendritic cells (DCs) dysfunction contributed to the immunosuppressive microenvironment in the lymph nodes (LNs) of TNBC patients following immunotherapy, which greatly affected the immunotherapeutic efficacy. Building on this, we introduce a chimeric exosomes-derived immunomodulator, EMV@SS-Toy, involving a polysulfide bond-bridged mesoporous silica nanoparticles (SS-MSN) as a reactive oxygen species (ROS) scavenger and responsive carrier nucleus, loading with the (IRE1a-XBP1) inhibitor toyocamycin (Toy) and coating with chimeric exosomes comprising DCs-derived exosomes and Salmonella outer membrane vesicles. This multifaceted immunomodulator can significantly enhance LNs' homing via homologous targeting and chemokine-guided navigation, enabling a pathological ROS-responsive drug release, dual-stress pathway regulation, thereby restoring and DCs' function and LNs' immune microenvironment. As expected, the immunomodulator markedly boosted the responsiveness of TNBC to immunotherapy, exerting potent inhibition on both the primary tumor and metastases and establishing long-term immune surveillance. Our study provides potent directions for translational immunotherapy through optimizing the LNs' microenvironment in TNBC. Overall design: To investigate the immunostimulatory potential of engineered extracellular vesicles (EMVs), we treated DC2.4 cells with EMV@SS and performed GO enrichment analysis to identify the immune-related gene expression changes.