A hydrogel-enabled cascade amplification of radiosensitization and immune activation for cancer radiotherapy

Hypofractionated radiotherapy (HRT) is a promising approach for tumor treatment, owing to its straightforward elimination of tumor cells and stimulation of immunogenic cell death. However, clinical application of HRT is hindered by the inherent radio-resistance and inadequate immune activation. Herein, an injectable hydrogel platform was reported, enabling a cascade amplification of radiosensitization and immune activation to potentiate HRT. The hydrogel with encapsulated TLR7/8 agonist R848 is in situ constructed in tumor via L-norvaline-based polymer (LNP, a gelator). During HRT, the released L-norvaline from LNP suppresses L-arginine consumption through arginase 1 (ARG1) pathway, sparing adequate L-arginine that was used for radiosensitizer nitric oxide (NO) production by inducible NO synthase (iNOS). Meanwhile, R848 repolarizes tumor-associated macrophages (TAMs) from M2 type with rich ARG1 to M1 type with rich iNOS, reinforcing NO production and disrupting M2-type TAMs-induced radio-resistance and immunosuppression. Therefore, the hydrogel demonstrates a cascade regulation of radio-sensitization and immune activation, achieving powerful inhibition of tumor growth and tumor metastasis. This hydrogel provides a novel approach to potentiate HRT, holding great promise in clinical application.