Rescue Radiosensitization of Pancreatic Cancer via PD-L1/TGF-β1 Dual-Blockade Nanotherapy as Evaluated in 3-Dimensional Microtumors

Radiation-induced immunological and stromal changes in the pancreatic tumor microenvironment (TME) often develop adaptive radioresistance in clinical. Among these changes, cellular compensatory programmed cell death-ligand 1 (PD-L1) overexpression induced by radiation will promote the adaptive immune evasion, limiting the radiation-mediated antitumor effect. Regrettably, the PD-L1 overexpression will be further potentiated by transforming growth factor-β1 (TGF-β1) that abundantly secreted by irradiated pancreatic stellate cells. This further fosters an immunosuppressive TME, which constitutes one of the key factors contributing to the limited efficacy of combining radiotherapy with programmed cell death protein 1 (PD-1)/PD-L1 blockade in pancreatic ductal adenocarcinoma. To counteract this resistance mechanism, we developed a TME-responsive nanogel (pirfenidone@nanogel-hyaluronidase-anti-PD-L1 [PFD@NGHP]) for rescuing radiosensitization. The PFD@NGHP is composed of a reduction-sensitive core encapsulating pirfenidone and a cationic surface corona of hyaluronidase and anti-PD-L1 antibodies. At the intercellular level, PFD@NGHP effectively inhibited TGF-β1 secretion by about 50% and targeted PD-L1 for antibody-dependent cell-mediated cytotoxicity. In the 3-dimensional stromal microtumors, PFD@NGHP effectively penetrated in stroma (>400 μm in depth), suppressed pancreatic stellate cells, and potentiated radiosensitization. In murine models, PFD@NGHP ameliorated the stroma through TGF-β1 inhibition, subsequently increased T cell infiltration of about 30% CD8⁺ T cells, and amplified the efficacy of PD-L1 blockade. This effect synergized radiotherapy to sustain tumor regression and generate abscopal effects. Collectively, our study demonstrates that PFD@NGHP targets the TGF-β1-PD-L1 axis in a cascading manner, offering a promising clinical strategy to overcome the adaptive radioresistance of irradiated pancreatic ductal adenocarcinoma while providing a potential platform for translational nanomedicine evaluation.