Purpose: Ewing sarcoma (EwS) is a highly aggressive bone- or soft tissue-associated malignancy mostly affecting children, adolescents, and young adults. Although multimodal therapies have strongly improved patients′ overall survival over the past decades, the development of prognostic biomarkers for risk-based patient stratification and more effective therapies with less adverse effects is stagnating. Thus, new personalized medicine approaches are urgently required. Experimental design: Gene expression data of EwS and normal tissues were crossed with survival data to identify highly overexpressed, prognostically relevant, and actionable potential targets. RNA-interference and dose-response assays as well as tissue-microarray analyses were carried out to explore the functional role and druggability of a prominent candidate gene in vitro and in vivo, and to validate its suitability as a prognostic biomarker. Results: Employing a multilayered screening approach, we discover ribonucleotide reductase regulatory subunit M2 (RRM2) as a promising therapeutic target and prognostic biomarker in EwS. Through analysis of two independent EwS patient cohorts, we show that RRM2 mRNA and protein overexpression is associated with an aggressive clinical phenotype and poor patients′ overall survival. In agreement, RRM2 silencing as well as pharmacological inhibition by the specific inhibitor triapine (3-AP) significantly reduces EwS growth in vitro and in vivo. Furthermore, we present evidence that pharmacological RRM2 inhibition by triapine can overcome chemoresistance against doxorubicin or gemcitabine, and synergize with cell cycle checkpoint inhibitors (CHEK1 or WEE1). Conclusions: Based on the aggressive phenotype mediated by and the druggability of RRM2 our results provide a translational rationale for exploiting RRM2 as a novel therapeutic target in EwS and prompt further clinical investigations.

中文翻译：

---

RRM2作为尤因肉瘤的预后生物标志物和治疗靶标的转化证据

目的：尤因肉瘤（EwS）是一种与骨或软组织相关的高度侵袭性恶性肿瘤，主要影响儿童，青少年和年轻人。尽管在过去的几十年中，多模式疗法极大地改善了患者的总体生存率，但基于风险的患者分层和不良反应更少，更有效的疗法的预后生物标志物的发展却停滞不前。因此，迫切需要新的个性化医学方法。实验设计：将EwS和正常组织的基因表达数据与生存数据进行交叉，以鉴定高度过表达，预后相关和可操作的潜在靶标。进行了RNA干扰和剂量反应分析以及组织微阵列分析，以探索重要候选基因在体外和体内的功能作用和可药用性，并验证其作为预后生物标志物的适用性。结果：采用多层筛选方法，我们发现核糖核苷酸还原酶调节亚基M2（RRM2）作为有希望的治疗靶标和EwS的预后生物标志物。通过对两个独立的EwS患者队列的分析，我们显示RRM2 mRNA和蛋白的过表达与侵略性临床表型和不良患者的总体生存率相关。一致的是，RRM2沉默以及特异抑制剂Triapine（3-AP）的药理抑制作用显着降低了体外和体内EwS的生长。此外，我们提供的证据表明，三氮平抑制RRM2的药理作用可以克服对阿霉素或吉西他滨的化学耐药性，并与细胞周期检查点抑制剂（CHEK1或WEE1）协同作用。结论：