Gene expression signature based screening in Ewing sarcoma

项目摘要 尤文肉瘤是一种高度侵袭性的骨和软组织癌症，由EWS-FLI 1融合引起 蛋白EWS-FLI 1癌蛋白部分地作为异常转录因子起作用，并且是 肿瘤生长和存活。然而，用药物直接靶向EWS-FLI 1一直具有挑战性， 因此，迫切需要确定EWS-FLI 1的下游目标和所产生的独特漏洞 被癌蛋白所控制为了鉴定EWS-FLI 1的下游靶点，我们使用人胚胎干细胞 表达诱导型EWS-FLI 1，以在遗传学上模拟尤文肉瘤的发生和发展。 定义系统。然后，我们使用这个模型系统和基于基因表达的方法来识别尤因， 肉瘤细胞对核糖核苷酸还原酶（RNR）抑制剂，包括吉西他滨， 其通过阻断脱氧核糖核苷酸的合成来损害DNA复制。此外，我们还 发现抑制尤文肉瘤细胞中的RNR导致复制应激，激活未折叠的 蛋白质反应，以及对受损DNA的反应所需的蛋白质合成的阻断 复制的值得注意的是，吉西他滨与检查点激酶1（CHK 1）抑制剂的组合，主要的免疫抑制剂， 调节剂的反应受损的DNA复制，结果协同作用，在体外和显着延长 异种移植实验中小鼠存活率的变化。在强有力的初步数据的指导下，我们现在将继续 具体目标如下：1）剖析未折叠蛋白激活和调控的分子基础 在用核糖核苷酸还原酶抑制剂处理的尤文肉瘤细胞中的反应; 2）测试体内功效 吉西他滨和第二代CHK 1抑制剂prexasertib，使用尤文肉瘤异种移植模型; 以及3）使用高通量筛选来测试使用我们的基因表达鉴定的候选疗法 基于方法的针对尤文肉瘤细胞的活性。这些目标将通过以下方式进行测试： 癌细胞系、细胞系异种移植物、患者来源的异种移植物以及我们的同基因、遗传学上的 确定的细胞系。这项工作将是重要的，因为它预计将有翻译的相关性， 治疗儿童和成人尤文肉瘤肿瘤，以及导致更广泛的理解， 尤文肉瘤肿瘤发生的基本机制。这项研究是创新的，因为它 整合了一种新的尤文肉瘤干细胞模型， 寻找新的治疗靶点。

PROJECT SUMMARY Ewing sarcoma is a highly aggressive bone and soft tissue cancer that is caused by the EWS-FLI1 fusion protein. The EWS-FLI1 oncoprotein functions, in part, as an aberrant transcription factor and is required for tumor growth and survival. However, directly targeting EWS-FLI1 with drugs has been challenging and, as a result, there is a critical need to identify downstream targets of EWS-FLI1 and unique vulnerabilities incurred by the oncoprotein. In order to identify downstream targets of EWS-FLI1, we used human embryonic stem cells that express inducible EWS-FLI1 to model the initiation and development of Ewing sarcoma in a genetically defined system. We then used this model system and a gene expression based approach to identify that Ewing sarcoma cells are uniquely vulnerable to inhibitors of ribonucleotide reductase (RNR), including gemcitabine, which impair DNA replication by blocking the synthesis of deoxyribonucleotides. Moreover, we have also identified that the inhibition of RNR in Ewing sarcoma cells results replication stress, activation of the unfolded protein response, and a block in the synthesis of proteins required for the response to impaired DNA replication. Notably, the combination of gemcitabine with an inhibitor of checkpoint kinase 1 (CHK1), the major regulator of the response to impaired DNA replication, results in synergy in vitro and a significant prolongation of mouse survival in xenograft experiments. Guided by strong preliminary data, we will now pursue the following specific aims: 1) dissect the molecular basis of the activation and regulation of the unfolded protein response in Ewing sarcoma cells treated with inhibitors of ribonucleotide reductase; 2) test the in vivo efficacy of gemcitabine and a second-generation CHK1 inhibitor, prexasertib, using Ewing sarcoma xenograft models; and 3) use high-throughput screening to test candidate therapeutics identified using our gene expression based approach for activity against Ewing sarcoma cells. These aims will be tested using a combination of approaches in cancer cell lines, cell line xenografts, patient-derived xenografts, and our isogenic, genetically defined cell lines. This work will be significant because it is expected to have translational relevance for the treatment of children and adults with Ewing sarcoma tumors, as well as lead to a broader understanding of the basic mechanisms of tumorigenesis in Ewing sarcoma tumors. The proposed research is innovative because it integrates a novel, stem cell model of Ewing sarcoma with a gene expression signature based screening approach to identify new therapeutic targets.