Cholesterolized TLR7 agonist liposomes combined with radiotherapy elicit antitumor immunity through oxidized mitochondrial DNA- driven inflammasome pathway

Background Radiotherapy is fundamental in the treatment of malignancies; however, its ability to consistently control tumor recurrence and metastases remains limited. There has been significant interest in exploring innovative immunomodulatory strategies that can enhance antitumor immunity by synergistically combining novel immunostimulatory agents with radiotherapy. The objective of this study was to investigate the antitumor efficacy and mechanism of cholesterolized TLR7 agonist liposomes, 1V209-Cho-Lip, in combination with radiotherapy. Methods Mouse tumor models were applied to validate the antitumor efficacy of 1V209-Cho-Lip combined with radiotherapy. Changes in the immune microenvironment were analyzed using flow cytometry. In vitro, primary mouse bone marrow-derived dendritic cells (BMDCs) were utilized to investigate the activated pathway. Casp1 ^−/− mice were used to confirm the crucial role of caspase-1 in the antitumor effect of 1V209-Cho-Lip combined with radiotherapy. Results The combination of 1V209-Cho-Lip with radiotherapy demonstrated a synergetic antitumor effect and reduced spontaneous lung metastasis in 4T1 and B16-F10 tumor models. This combined therapy effectively promated dendritic cell (DC) maturation and activated effector and memory CD8 ⁺ T cells. Specifically, oxidized mitochondria DNA (ox-mtDNA) released from irradiated tumor cells, as DAMPs, synergized with 1V209-Cho-Lip to activate the inflammasome pathway in DC, leading to the production of interleukin-1β (IL-1β) and maturation of DC. The antitumor efficacy of 1V209-Cho-Lip combined with radiotherapy was impaired in Casp1 ^−/− mice. Conclusions Our findings highlight the potential of combining 1V209-Cho-Lip and RT as a promising anticancer treatment strategy, providing a proof-of-concept for translation to early-phase clinical trials.