Intracellular Disulfide Stress Induced Actin Dysfunction for Enhancing Radiotherapy Sensitivity and Eliciting Antitumor Immunity

Radiotherapy (RT) is a primary modality in cancer treatment, with its efficacy dependent on tumor radiosensitivity. This study presents a cystine-inserted layered double hydroxide nanosheet loaded with phloretin (CLDHP) to enhance RT sensitivity by inducing G2/M phase arrest through disulfide stress. In acidic microenvironments, CLDHP undergoes degradation, enabling the release of cystine and phloretin. Phloretin inhibits glucose transporter type 1, blocking the pentose phosphate pathway and leading to NADPH depletion. The resulting NADPH depletion exacerbates cystine accumulation, activates disulfide stress, and induces disulfide cross-linking of cellular actin, arresting tumor cells at the radiation-sensitive G2/M phase. In vivo studies reveal that CLDHP markedly augments RT sensitivity and effectively inhibits tumor growth. Furthermore, combining CLDHP with an immune checkpoint inhibitor boosts RT-induced antitumor immune responses, demonstrating excellent efficacy against X-ray-irradiated primary tumors and inhibiting the growth of distant and metastatic tumors. This work highlights the role of disulfide stress in inducing G2/M phase arrest, offering a safe and effective radiosensitization strategy.