Abstract LB046: Mitochondrial damage-associated molecular pattern (damp)-mediated chronic stingactivation shapes the immune microenvironment in pancreatic cancer

Abstract Background: STING agonists have emerged as a promising strategy in tumor immunotherapy. However, their overall efficacy is constrained by several limiting factors. Studies indicate that chronic activation of the STING pathway can facilitate tumor immune evasion through the secretion of pro-inflammatory factors. Pancreatic ductal adenocarcinoma (PDAC), a highly aggressive gastrointestinal malignancy, is notably resistant to immunotherapy. Thus, understanding the role of STING signaling in shaping the immune microenvironment of PDAC is crucial for evaluating its potential as a therapeutic target. Methods: This study utilized multiplex immunofluorescence staining (mIHC) and spatial transcriptomics to delineate the immune microenvironment in PDAC patient samples. Differential gene expression analysis was conducted using bulk RNA sequencing and single-cell RNA sequencing. Both single-cell sequencing and bulk RNA sequencing were employed in genetically engineered mouse mode (LSL-KrasG12D/+,LSL-Trp53R172H/+,McuLSL/+,Pdx-1-Cre mice) to investigate intercellular communication networks. Specific immune cell subsets were further validated through flow cytometry. Results: Our findings revealed that STING signaling was significantly activated in tumor samples from PDAC patients, with activation levels strongly associated with disease stage, tumor differentiation, and prognosis. Single-cell transcriptomic analysis identified a distinct population of STING-activated ductal epithelial cells, characterized by high enrichment of mitochondrial DAMP pathways and close interactions with myeloid-derived suppressor cells (MDSCs). Multi-omics analyses identified the mitochondrial calcium uniporter (MCU) as a key regulator of mitochondrial STING activation. In vitro and in vivo experiments demonstrated that MCU-overexpressing tumor cells robustly activated the STING pathway, exhibited spatial colocalization with CCR2+MDSCs, and induced the exhaustion of CD8+T cells and antigen-presenting cells in the immune microenvironment. Mechanistically, MCU activation triggered mitochondrial permeability transition pore (mPTP) opening, leading to sustained DAMP release. Virtual drug screening identified SBI-993 as a potent MCU inhibitor. Treatment with SBI-993, in combination with AG chemotherapy and anti-PD-1 therapy, significantly reduced tumor burden in vivo. Conclusions: This study underscores the pivotal role of mitochondrial dysfunction in chronic STING activation and immune evasion in PDAC. It further highlights the detrimental accumulation of MDSCs as a consequence of sustained STING activation. Targeting MCU with specific inhibitors, in combination with immunotherapy, offers a promising therapeutic strategy for combating pancreatic cancer. Citation Format: Zekun Li, Yunzhan Li, Yongjie Xie, Mengzhe Zhang, Bo Ni, Chenyang Meng, Guangcong Shen, Boyang Fu, Yueying Shan, Jun Yu, Jihui Hao, Xiuchao Wang. Mitochondrial damage-associated molecular pattern (damp)-mediated chronic stingactivation shapes the immune microenvironment in pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 2 (Late-Breaking, Clinical Trial, and Invited Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_2):Abstract nr LB046.