1138 - ADAR1 Expression in CD8<sup>+</sup> T Cells Modulates Radiotherapy Response and Prognosis in Non-Small Cell Lung Cancer via Disrupting Mitochondrial Function
Presenter(s)
C. Tian1,2, F. Wang2, S. Bao2, J. Ma2, H. Yang2, J. Liu2, J. Wang2, Y. Wang, M. Wu4, J. Yu4,5, and D. Chen2,6; 1Department of Radiation Oncology, National Cancer Center/National Clinical Research Center for Cancer/Cancer Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China, 2Shandong Provincial Key Laboratory of Precision Oncology, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, China, 3Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, Shandong, China, 4Department of Radiation Oncology, Shandong Cancer Hospital and Institute, Shandong First Medical University and Shandong Academy of Medical Sciences, Jinan, 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
Purpose/Objective(s):
The functional integrity of tumor-infiltrating immune cells, particularly CD8+ T cells, is critical for antitumor immunity and therapeutic efficacy. Adenosine deaminase acting on RNA 1 (ADAR1), an RNA-editing enzyme implicated in cancer progression, remains poorly understood in immune cells and its clinical relevance to radiotherapy outcomes in non-small cell lung cancer (NSCLC). This study investigated the prognostic significance of ADAR1 in CD8+ T cells and explores its mechanistic role in regulating radiotherapy response in NSCLC.Materials/Methods:
Single-cell and spatial transcriptomic analyses were employed to profile ADAR1 expression across immune subsets in NSCLC cohorts. Multiplexed immunofluorescence (mIF) was used to validate the ADAR1 expression in CD8+ T cells across different regions and its association with patient prognosis in NSCLC. TCROT-1 CD8+ T cells were adoptively transferred or co-cultured with OVA-coated NSCLC cells to evaluate antigen-specific cytotoxicity in vivo and in vitro. Antisense oligonucleotides and 8-Azaadenosine were utilized for genetic and pharmacological ADAR1 inhibition. Flow cytometry was employed to assess CD8+ T cell function and reactive oxygen species (ROS) levels. Electron microscopy and JC-1 assays were utilized to evaluate mitochondrial damage, while ATP production analysis and oxygen consumption rate (OCR) measurement were used to assess mitochondrial function. Western blotting (WB) and reverse transcription quantitative polymerase chain reaction (RT-qPCR) were employed to detect the protein and mRNA expression levels of the gene.Results:
Elevated ADAR1 expression was observed in CD8+ T cells within the tumor region, correlating with poor radiotherapy response (high vs. low ADAR1: 33.33% vs. 71.43%) and short progression-free survival (PFS) (hazard ratio (HR) = 2.91, 95% confidence interval (CI) 1.06–7.96; P = 0.037). Targeting ADAR1 in CD8+ T cells enhanced radiotherapy efficacy in vivo and in vitro. ADAR1 inhibition reduced apoptosis, increased activation, improved cytotoxicity, and bolstered memory capacity of CD8+ T cells. This effect was achieved by reducing reactive oxygen species (ROS) accumulation and preserving mitochondrial integrity and function. CD38, a negative regulator of ROS clearance and CD8+ T cell function, was screened out and confirmed as the downstream target of ADAR1 in CD8+ T cells.Conclusion:
In this study, we identified the mean fluorescence intensity (MFI) of ADAR1 in CD8+ T cells within the tumor region as a reliable prognostic predictor in NSCLC (area under the curve (AUC) = 0.805). Mechanistically, ADAR1 inhibition in CD8+ T cells improved survival and anti-tumor effects of CD8+ T cells by preserving mitochondrial function through the CD38-ROS axis. Our findings fill a gap in understanding the role of ADAR1 in CD8+ T cells, emphasizing its potential as a biomarker and therapeutic target to enhance tumor control in NSCLC.