ESTRO 2025 - Abstract Book

S3994

Radiobiology - Tumour radiobiology

ESTRO 2025

Purpose/Objective: Metabolic reprogramming critically contributes to therapy resistance, including radiotherapy. Decoding metabolic pathways thus appears to be a promising and powerful new tool for cancer target identification in the era of precision medicine. This study in triple-negative breast cancer (TNBC) aimed at elucidating changes in the metabolism of TNBC cells upon X-ray irradiation and to test for exploitable approaches to overcome radioresistance by targeting a specific, particularly vulnerable metabolic pathway. Material/Methods: Liquid chromatography high-resolution tandem mass spectrometry-based un-/targeted metabolomics was conducted in MDA-MB-231 cells after irradiation. MetaboAnalyst and STRING were used for metabolite identification, their metabolic pathways and interactive networks to eventually target the associated enzymes. An RNAi screen of these enzymes determined their cytotoxic and radiosensitizing potential. Knockdown efficiency of siRNA was confirmed by western blotting. Top radiosensitizing enzymes were analyzed in the METABRIC dataset regarding overall survival (OS) of TNBC patients. Cellular survival was tested by colony formation assay, DNA damage by γH2AX foci assay and cell cycling by PI staining in a larger cell model panel. Results: Untargeted metabolomics revealed 35 significantly changed metabolites (out of 748) in irradiated cells relative to controls. By harnessing metabolite-enzyme interaction networks, 44 potentially targetable enzymes were identified. Among these, eight demonstrated radiosensitizing potential upon depletion, a finding associating with the clinical endpoint OS using the METABRIC datasets. PKM, with high PKM expression linked to significantly worse OS in the METABRIC cohort, emerged as the most promising target, showing stronger radiosensitization in all six investigated cell models upon knockdown and pharmacological inhibition by compound 3K. The radiosensitization was accompanied by a significant increase in S-phase associated yH2AX and G2-phase arrest. Targeted metabolomic analysis of glycolysis and TCA cycle after PKMi and X-ray irradiation revealed accumulation of metabolites (e.g. phosphoenolpyruvate and 3-P-glycerate) of both pathways. Four genes related to these metabolites displayed a positive correlation with PKM expression. TNBC patients with low co-expression of these genes who received radiotherapy showed a significantly better OS than patients with high co-expression. Conclusion: These data suggest that PKM and its association with glycolysis and TCA cycle plays a critical role in the radioresponse of human TNBC cell models. Further unraveling of the metabolism may open up new avenues to enhance treatment strategies and broaden therapeutic options for TNBC patients.

Keywords: Metabolomics, Radiosensitization, Targeted Therapy

2487

Digital Poster The orphan genes CCDC97 is involved in radiotherapy response in ER+ breast cancer cells. Assia Duatti 1 , Ylenia Martinini 1 , Cinzia Talamonti 2 , Chiara Mattioli 3 , Mauro Loi 3 , Giulio Francolini 3 , Vanessa Di Cataldo 3 , Luca Visani 3 , Viola Salvestrini 3 , Carlotta Becherini 3 , Icro Meattini 3 , Monica Mangoni 3 , Lorenzo Livi 3 1 Department of Experimental and Clinical Biomedical Sciences, University of Florence, Florence, Italy. 2 Radiation Oncology Physics Unit, Careggi Hospital, Univesrity of Florence, Florence, Italy. 3 Radiation Oncology, Careggi Hospital, Univesrity of Florence, Florence, Italy Purpose/Objective: Radiotherapy (RT) is an integral part of the multidisciplinary management of breast cancer (BC). Radiation therapy can be used potentially at every stage of the disease, from the primary to the metastatic setting. Unfortunately, not all patients that receive RT will obtain therapeutic benefits, as cancer cells either possess intrinsic radio-resistance