2535 - OIP5 Mediates Radiotherapy Resistance in Lung Adenocarcinoma through POLD1-Dependent DNA Damage Repair
Presenter(s)
S. Zeng1,2, J. He3,4, D. Tao5, W. Zhou1, and Y. Z. Wu1; 1Department of Radiation Oncology, Chongqing University Cancer Hospital, Chongqing, China, 2School of Medicine, Chongqing University, Chongqing, Chongqing, China, 3Radiation Oncology Center, Chongqing University Cancer Hospital, Chongqing, China, 4School of Medicine, Chongqing University, Chongqing, China, 5Department of Radiation Oncology, Chongqing University Cancer Hospital, Chongqing, China, China
Purpose/Objective(s): The cancer/testis antigen OIP5 is implicated in malignant progression and chemoresistance across various cancers; however, its role in lung adenocarcinoma (LUAD) radiosensitivity remains elusive. This study investigates the molecular mechanism by which OIP5 confers radiotherapy resistance in LUAD.
Materials/Methods: OIP5 expression in lung adenocarcinoma versus adjacent tissues was analyzed by immunohistochemistry and Western blot. Radiosensitivity was assessed via colony formation assays and murine xenograft models. DNA damage dynamics were quantified using comet assays, while HR/NHEJ/BIR repair efficiencies were measured via I-SceI reporter systems and DNA fiber assays. Chromatin fractionation tracked OIP5's DNA-binding dynamics post-irradiation. OIP5 interactomes post-IR were profiled by mass spectrometry, filtered through GO DNA repair gene sets, and validated by co-IP. Immunofluorescence mapped OIP5 subcellular redistribution.
Results: OIP5 expression was significantly higher in tumor tissues compared to adjacent normal tissues. Knockdown of OIP5 enhanced radiosensitivity of LUAD cells both in vitro and in vivo, accompanied by suppression of DNA damage repair, particularly in HR and its specialized form, BIR. Ionizing radiation (IR) induced transient upregulation of OIP5 in A549 and H1299 cells, peaking at 1h post-IR, and promoted its nuclear translocation and chromatin binding. Mass spectrometry analysis identified POLD1 as the primary DNA repair protein interacting with OIP5 following IR. Depletion of OIP5 reduced chromatin-bound POLD1 levels while silencing POLD1 reversed the OIP5 overexpression-induced radioresistance and enhanced DNA repair efficiency.
Conclusion: OIP5 coordinates with POLD1 through IR-induced nuclear translocation to potentiate BIR repair, driving radiotherapy resistance in LUAD. Therapeutic targeting of the OIP5-POLD1 axis may represent a novel radiosensitization strategy.