Dose-response assays revealed that EwS cells were very sensitive towards triapine compared to osteosarcoma cells and non-transformed EwS patient-derived mesenchymal stem cells (mean IC SB 50 sb values 0.35, 1.63, 101.63 µM, respectively) (Fig. Keywords: Ewing sarcoma; RRM2; Targeted therapy; Prognostic biomarker; Paediatric oncology; Triapine; Chemoresistance EN Ewing sarcoma RRM2 Targeted therapy Prognostic biomarker Paediatric oncology Triapine Chemoresistance 1 7 7 07/30/21 20210727 NES 210727 Supplementary Information The online version contains supplementary material available at https://doi.org/10.1186/s12943-021-01393-9. To gain first insights into the biological function of I RRM2 i in EwS, we carried out gene ontology (GO) enrichment analysis of I RRM2 i co-expressed genes in 166 EwS tumours, which revealed that high I RRM2 i expression is closely correlated with cell proliferation-associated gene signatures (Fig. Pearson correlation coefficients between RRM2 and other genes were determined, of which those with |rPearson|> 0.5 were further analysed by GO enrichment analysis. f Kaplan-Meier survival analysis of 122 EwS patients stratified by RRM2 protein expression (low IRS <= 2, high IRS > 2). [Extracted from the article]