Presenter(s)
I. Dokic1,2, F. Ciamarone1,2, D. C. Hoffmann3, D. I. Filosa1,2, J. Bojcevski1,2, D. Krunic4, T. Tessonnier1,2, J. Debus5,6, A. Mairani1,2, V. Venkataramani3, and A. Abdollahi1,2; 1Clinical Cooperation Unit Translational Radiation Oncology, National Center for Tumor Diseases (NCT), Heidelberg University Hospital (UKHD) and German Cancer Research Center (DKFZ), Heidelberg, Germany, 2Division of Molecular and Translational Radiation Oncology, Department of Radiation Oncology, Heidelberg Faculty of Medicine (MFHD), Heidelberg University Hospital (UKHD) and Heidelberg Ion-Beam Therapy Center (HIT), Heidelberg, Germany, 3Department of Neurology Heidelberg University Hospital (UKHD), National Center for Tumor Diseases (NCT) and Clinical Cooperation Unit Neurooncology German Cancer Research Center (DKFZ), Heidelberg, Germany, 4Light Microscopy Facility, German Cancer Research Center (DKFZ), Heidelberg, Germany, 5Clinical Cooperation Unit Radiation Oncology, German Cancer Research Center (DKFZ), National Center for Tumor Diseases (NCT), Heidelberg, Germany, 6Department of Radiation Oncology, Heidelberg Faculty of Medicine (MFHD), Heidelberg University Hospital (UKHD) and Heidelberg Ion-Beam Therapy Center (HIT), Heidelberg, Germany
Purpose/Objective(s): Tumor microtubes (TMs) form functional multicellular networks in glioblastoma (GB) and contribute to radioresistance. Conventional X-ray irradiation enhances TM formation, further promoting treatment resistance. We hypothesized that high linear energy transfer (LET) particle radiotherapy may circumvent TM-mediated resistance due to its reduced dependence on indirect DNA damage. This study investigates how LET-dependent DNA damage influences TM formation and GB cell survival.
Materials/Methods:
TM formation was assessed in two primary patient-derived glioblastoma stem-like cell lines (S24 and T269) irradiated using particle beams with LET values from 3–107 keV/µm. Dose series of 1, 2, 4, and 6 Gy were delivered using clinical proton, helium, and carbon-ion beams. TM networks and radiation-induced DNA damage (?H2AX foci) were visualized by fluorescence microscopy. Transcriptome was analyzed and gene signatures for each treatment were compared to the established GB TM connectivity signatures. Clonogenic survival assays quantified treatment response.Results:
TM formation, DNA-damage complexity, and GB cell survival showed clear LET-dependent patterns. Low-LET proton irradiation increased TM formation in a dose-dependent manner, similar to photon responses. In contrast, higher LET progressively reduced TM induction and network connectivity while generating more complex DNA damage. Gene-expression profiling supported these structural findings: control cells displayed strong alignment with the clinically relevant 71-gene TM-connectivity signature, whereas higher-LET treatments led to downregulation of connectivity-associated genes, indicating disruption of TM-mediated communication programs. Functionally, increasing LET resulted in reduced clonogenic survival, with the strongest cytotoxicity observed after high-LET carbon-ion irradiation. The inverse LET–TM relationship was consistently reproduced across the LET range modulated within carbon-ion beams.Conclusion:
High-LET particle therapy disrupts TM mediated cellular connectivity, a significant driver of treatment resistance in glioblastoma. By suppressing these resistance networks and enhancing lethal DNA damage, high-LET modalities such as carbon ions offer a mechanistically targeted strategy to improve radiotherapy effectiveness and potentially extend clinical benefit for patients with GB.