Glutathione Depletion‐Induced Versatile Nanomedicine for Potentiating the Ferroptosis to Overcome Solid Tumor Radioresistance and Enhance Immunotherapy

A high level of reduced glutathione is a major factor contributing to the radioresistance observed in solid tumors. To address this radioresistance associated with glutathione, a cinnamaldehyde (CA) polymer prodrug, referred to as PDPCA, is fabricated. This prodrug is created by synthesizing a pendent CA prodrug with acetal linkages in a hydrophobic block, forming a self-assembled into a core-shell nanoparticle in aqueous media. Additionally, it encapsulates all-trans retinoic acid (ATRA) for synchronous delivery, resulting in PDPCA@ATRA. The PDPCA@ATRA nanoparticles accumulate reactive oxygen species through both endogenous and exogenous pathways, enhancing ferroptosis by depleting glutathione. This approach demonstrates efficacy in overcoming tumor radioresistance in vivo and in vitro, promoting the ferroptosis, and enhancing the cytotoxic T lymphocyte (CTL) response for lung tumors to anti-PD-1 (αPD-1) immunotherapy. Furthermore, this study reveals that PDPCA@ATRA nanoparticles promote ferroptosis through the NRF2-GPX4 signaling pathway, suggesting the potential for further investigation into the combination of radiotherapy and αPD-1 immune checkpoint inhibitors in cancer treatment.