Also, consistent with previous reports (35, 40, 41), we observed an increase in both the percentage of cells in late-S–G2–M and the level of phospho-CDK1 (Y15) in the Ewing sarcoma cells upon 8–24 hours treatment with two independent DDKis, TAK-931 and XL413 (Supplementary Fig. S2A–C), further suggesting that DDK inhibition induces a molecular inhibition of mitotic entry. Here, CDK1 is linked to Ewing sarcoma.