In situ genetically engineering nanosystem for reversing immunosuppression of cancer-associated fibroblasts in breast cancer radiotherapy.

Adjuvant radiotherapy (RT) for breast cancer can activate cancer-associated fibroblasts (CAFs), leading to reduced efficacy of immunotherapy and even tumor recurrence. Pathological analysis of breast cancer reveals that the PD-L2 upregulation in CAFs induces T cell exhaustion, resulting in RT-induced immunogenic cell death (ICD) being insufficient to trigger durable systemic antitumor immunity. Based on this discovery, CAFs targeted genetically engineering nanosystems (named PFPEI@αPC NPs) are fabricated to prevent breast cancer recurrence after adjuvant RT. PFPEI@αPC NPs achieve CAFs targeted gene delivery through PD-L2 recognition, ensuring an efficient gene transfection and CAFs editing in situ. This approach reprograms CAFs into antigen-presenting cells expressing CD86 costimulatory signals, while concurrently producing αPD-L1 antibodies. The engineered CAFs reactivate tumor-specific T-cell immunity, alleviate T-cell exhaustion, and block PD-L1-mediated immune escape. Combined with RT, this strategy generates central memory T cells that eradicate metastatic tumors and prevent recurrence in rechallenged models. Our work elucidates a mechanism to counteract RT-induced immunosuppression, providing a synergistic strategy to enhance immunotherapy against breast cancer recurrence.