321 - Low-Dose Radiotherapy Modulates Dendritic Cell Metabolism to Reprogram the Tumor Immune Microenvironment
Presenter(s)
Y. Zhou1, J. Yuan2, S. Yang1, B. Liu3, Z. Zhang4, Y. Dong4, D. Chen5, and N. Liu1,6; 1Tianjin Medical University Cancer Institute & Hospital, National Clinical Research Center for Cancer,Tianjin’s Clinical Research Center for Cancer,Key Laboratory of Cancer Prevention and Therapy, Tianjin, Tianjin, China, 2Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, Shandong, China, 3College of Arts and Sciences, Lehigh University, Bethlehem, PA, 4Shandong Cancer Hospital and Institute, Jinan, Shandong, China, 5Department of Radiation Oncology and Shandong Provincial Key Laboratory of Precision Oncology, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, China, 6Hetian District People’s Hospital, Hetian District, China
Purpose/Objective(s): Low dose radiotherapy (LDRT) is an emerging clinical approach that effectively overcomes resistance to immune checkpoint inhibitors (ICIs). However, the immunomodulatory mechanisms driving its efficacy, beyond direct tumor cytotoxicity, remain poorly understood. Our clinical findings suggest that LDRT may reverse ICIs resistance in advanced non-small cell lung cancer patients, potentially through the activation of dendritic cells (DCs). This study aims to investigate how LDRT regulates DC metabolism and inflammatory responses, validating its role in reshaping the tumor immune microenvironment (TIME) and enhancing antitumor efficacy when combined with ICIs.
Materials/Methods: In vitro, DC2.4 cells and C57BL/6 bone marrow-derived DCs (BMDCs) were exposed to fractionated X-ray irradiation (0, 0.25, 0.5, 0.75, or 1 Gy × 3 fractions). RNA sequencing was employed to investigate the effects of LDRT on gene expression in BMDCs. The maturation and function of DCs were detected using flow cytometry (FCM). The mechanisms by which LDRT influences DC activation were systematically investigated using Western blot analysis and qPCR. ELISA were performed to detect chemokines affecting DC function. In vivo, we evaluated the antitumor efficacy of LDRT (1 Gy/fraction × 5 fractions) combined with PD-1 antibody using a Lewis lung carcinoma tumor-bearing mouse model. FCM was used to assess immune cell infiltration and the maturation status of DCs within the TIME.
Results: The results of our precisely designed LDRT gradient experiment clearly show that LDRT (0.5 Gy × 3) strongly promotes the maturation of BMDCs. This is accomplished through the most activation of the Keap1/Nrf2 signaling pathway, corroborated by RNA sequencing and the marked increase in Nrf2 protein levels. This activation triggered upregulation of glycolytic genes (HK2, PFKM, GLUT1), driving a metabolic shift toward aerobic glycolysis in DCs. Concurrently, LDRT increased expression of antioxidant genes (GCLC) and inflammatory cytokines (IL-6, TNF-a, IFN-?), further boosting DC activation. In vivo studies have revealed that, in contrast to monotherapies with limited efficacy, the combination therapy of LDRT and PD-1 antibody significantly suppressed tumor growth. FCM analysis within the TIME showed enhanced infiltration of CD8+ T cells. Furthermore, there was a marked increase in DC infiltration in both the TIME and tumor-draining lymph nodes. Notably, the proportion of CD80+CD86+DCs was significantly higher in the combination group, indicating enhanced DC activation.
Conclusion: Our research confirms that LDRT activates the Keap1/Nrf2 pathway, synergistically modulating DC metabolism, antioxidant defense, and inflammation. This process enhances DC-mediated antigen presentation and promotes CD8+ T cell recruitment, thereby reversing the immunosuppressive TIME and improving ICI efficacy. The present study offers a theoretical foundation for optimizing clinical strategies that integrate LDRT with ICIs.