The treatment of Ewing sarcoma, an aggressive bone and soft tissue sarcoma, is associated with suboptimal outcomes and significant side-effects. Consequently, there is an urgent need to identify novel therapies that will improve outcomes for children and adults with Ewing sarcoma tumors while also decreasing treatment-related toxicities. We analyzed data from the PRISM drug repurposing screen, which tested the activity of 4518 drugs across 578 cancer cell lines, to identify drugs that selectively inhibit the growth of Ewing sarcoma cell lines. We then tested the effects of a top hit from the screen on cell proliferation, cell cycle progression, and activation of the DNA damage pathway using Ewing sarcoma cell lines. We also used a CRISPR/Cas9 gene knockout approach to investigate the role of Schlafen 11 (SLFN11), a restriction factor for DNA replication stress that is overexpressed in Ewing sarcoma tumors, in mediating the sensitivity of Ewing sarcoma cells to the drug. We found that eltrombopag, an FDA-approved thrombopoietin-receptor agonist (TPO-RA) that is currently being evaluated as a treatment for chemotherapy-induced thrombocytopenia, inhibits the growth of Ewing sarcoma cell lines in vitro in proliferation and colony formation assays. However, from a mechanistic standpoint, the thrombopoietin receptor is not expressed in Ewing sarcoma cells and we show that eltrombopag impairs DNA replication and causes DNA damage in Ewing sarcoma cells by chelating iron, a known “off-target” effect of the drug. We also found that the sensitivity of Ewing sarcoma cells to eltrombopag is mediated, in part, by SLFN11, which regulates the cellular response to DNA replication stress. Ewing sarcoma cell lines are sensitive to eltrombopag and this drug could improve outcomes for patients with Ewing sarcoma tumors by both targeting the tumor, via chelation of iron and inhibition of DNA replication, and reducing chemotherapy-induced thrombocytopenia, via stimulation of the thrombopoietin receptor.

中文翻译：

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Eltrombopag通过铁螯合和DNA复制受损抑制尤文氏肉瘤细胞的增殖

尤因肉瘤是一种侵袭性的骨和软组织肉瘤，其治疗效果欠佳，且有明显的副作用。因此，迫切需要找到新的疗法，以改善尤因肉瘤肿瘤的儿童和成人的预后，同时减少与治疗有关的毒性。我们分析了PRISM药物再利用筛选中的数据，该数据测试了578种癌细胞系中4518种药物的活性，以鉴定选择性抑制尤因肉瘤细胞系生长的药物。然后，我们使用Ewing肉瘤细胞系测试了筛选对细胞增殖，细胞周期进程和DNA损伤途径激活的影响。我们还使用了CRISPR / Cas9基因敲除方法来研究Schlafen 11（SLFN11）的作用，介导尤因肉瘤细胞对药物的敏感性的一种在尤因肉瘤肿瘤中过度表达的DNA复制压​​力的限制因子。我们发现eltrombopag是FDA批准的血小板生成素受体激动剂（TPO-RA），目前正在评估其作为化学疗法诱导的血小板减少症的治疗方法，它在体外通过增殖和集落形成试验抑制尤因肉瘤细胞系的生长。然而，从机理的角度来看，血小板生成素受体在尤文氏肉瘤细胞中不表达，并且我们显示eltrombopag通过螯合铁而损害尤文氏肉瘤细胞中的DNA复制并引起DNA损伤，这是该药物的“脱靶”效应。我们还发现，尤因肉瘤细胞对Eltrombopag的敏感性部分是由SLFN11介导的，调节细胞对DNA复制压​​力的反应。尤文氏肉瘤细胞系对Eltrombopag敏感，该药物可通过螯合铁并抑制DNA复制来靶向肿瘤，并通过刺激血小板生成素受体减少化疗诱导的血小板减少，从而改善尤文氏肉瘤患者的预后。