Fig. 2

Triapine inhibits EwS growth in vitro and in vivo and synergise with cell cycle checkpoint inhibitors in vitro. a Dose–response analysis of triapine in EwS, osteosarcoma and mesenchymal stem cells. b Analysis of clonogenic growth of A-673, TC-71, and EW-7 EwS cells upon triapine treatment. c Left: Dose–response analysis of triapine in chemoresistant EwS cells (A-673/DR or A-673/GR). Right: magnitudes of doxorubicin or gemcitabine resistance shown by fold increase in IC₅₀ compared to those of parental cells. d Analysis of tumour growth upon triapine treatment in A-673 cell line in vivo. Images of resected xenografts (upper), tumour growth (lower left), and tumour weight at the experimental endpoint (lower right) of NSG mice xenografted with A-673 EwS cells upon treatment with triapine. Once tumours reached 5 mm in average diameter, animals were randomized in treatment group (30 mg/kg i.p.) or control group (DMSO) (n = 8 animals per group). The arrow indicates treatment start. Horizontal bars represent means and whiskers SEM. P-values were calculated at the experimental endpoint with two-sided (tumour growth) or one-sided (tumour weight) Mann–Whitney test. e Integrative Gene Ontology (GO) enrichment analysis of gene expression microarray data generated in A-673 and ES7 cells after RRM2 silencing or pharmacological RRM2 inhibition by triapine (corresponding IC₅₀ of 0.44 µM or 0.65 µM, respectively). f Correlation of gene expression between RRM2 and CHEK1 or WEE1 in 166 EwS. Each dot represents an individual expression value. Solid red lines indicate a trend line created by a simple linear regression. P-values were calculated by a two-tailed t-test. g Drug interaction and combination efficiency analysis between triapine and CHEK1 inhibitor (CCT245737) or WEE1 inhibitor (MK-1775) in 4 EwS cell lines (A-673, ES7, EW-7, TC-71) assessed by combination index. CI value < 1 indicative of synergistic, CI = 1 additive, and CI > 1 antagonistic h Drug interaction and combination efficiency estimation between triapine and CHEK1 inhibitor (CCT245737) or WEE1 inhibitor (MK-1775) in A-673 EwS cell line assessed by SynergyFinder 2.0. ZIP synergy score > 10, likely to be synergistic; between –10 and 10, likely to be additive; < –10, likely to be antagonistic