Splicing factors as therapeutic targets for the treatment of ovarian cancer

描述(由申请者提供)：每年有超过25,000名美国女性罹患卵巢上皮癌，其中50%的女性将死于她们的疾病，特别是如果被诊断为晚期疾病，这是很常见的。为了开发这种疾病的新疗法，有必要更好地了解与肿瘤转化相关的分子事件。选择性剪接(AS)允许从单个基因产生多种蛋白质异构体，在扩大后生动物蛋白质组的复杂性和适应内外环境变化方面发挥着重要作用。一般来说，与正常组织相比，肿瘤中更多的基因，特别是那些与肿瘤发生相关的基因，表现出不同的剪接形式。越来越多的证据表明，AS与肿瘤的进展和/或转移有关，并可能参与其中。目前，导致癌症剪接改变的机制尚不清楚，但它们可能是由于顺式元件的突变，或者更有可能是反式作用因子的变化，如剪接因子。事实上，几种剪接因子，包括PTB和SRp20，在肿瘤中过度表达，其中一种，SF2/ASF，被证明是癌基因。PTB和SRp20在人卵巢肿瘤中高表达，而正常卵巢上皮中PTB不表达或表达水平很低，并且这些SFs的表达与这些肿瘤的恶性程度有关。通过siRNA在体外敲除卵巢肿瘤细胞中的PTB，显著抑制了卵巢肿瘤小鼠的肿瘤细胞生长、克隆形成和侵袭性，并导致了肿瘤的缓慢生长。我们的结果提供了一个原则证明，剪接因子可能是一类新的和未被探索的癌症治疗靶点，至少在卵巢癌中是如此，这种疾病的结果令人沮丧，而且没有好的治疗选择，特别是对晚期疾病。在这项提案中，我们重点关注一种剪接因子PTB和一种肿瘤类型EOC，并假设PTB是这种疾病的可用药治疗靶点。为了验证我们的假设，我们建议开发一种基于细胞的高通量小分子文库筛选，以识别干扰PTB活性的小分子，然后研究这些已识别的小分子是否能够抑制卵巢肿瘤的生长。为此，我们提供了三个具体目标：(1)开发和优化专有的基于细胞的报告系统，以监测PTB在细胞中的活性；(2)开发和优化高通量筛选(HTS)小分子文库，包括那些包含FDA批准的小分子以及天然来源提取物或通过化学合成产生的化合物以识别PTB抑制剂的小分子文库；以及(3)验证有效的小分子对卵巢肿瘤细胞体外和体内生长的影响。如果成功，我们的方法将验证PTB作为一种新的治疗靶点，并将基于选择性剪接的操作确定一类新的小分子药物，用于治疗卵巢癌，可能还有其他上皮性癌症。与公共卫生相关：每年有超过25,000名美国女性罹患卵巢上皮癌，其中50%的女性将死于她们的疾病，特别是如果被诊断为晚期疾病，这是很常见的。如果成功，这里提出的研究将验证靶向剪接因子和替代剪接作为治疗卵巢癌和其他癌症的一种新的治疗方法。在项目期结束时，我们将发现导致治疗这些癌症的新药的小分子，这显然将对公众健康产生积极影响。

DESCRIPTION (provided by applicant): Epithelial ovarian cancer (EOC) strikes more than 25,000 American women annually, and >50% of these women will die from their disease, especially if diagnosed, as is common, with late-stage disease. To develop new therapies for this disease, it will be necessary to better understand the molecular events that are associated with the neoplastic transformation. Alternative splicing (AS), by allowing production of multiple protein isoforms from a single gene, plays a major role in expanding proteomic complexity in metazoans and adaptations to internal and external environmental changes. In general, more genes in tumors, especially those associated with tumorigenesis, exhibit alternative splice forms compared to normal tissues. There is mounting evidence that AS is associated with and possibly involved in tumor progression and/or metastasis. At present, the mechanisms leading to splicing alterations in cancer are poorly understood, but they are likely due either to mutations in cis-elements or, more likely, changes in trans-acting factors, such as splicing factors. Indeed, several splicing factors, including PTB and SRp20, are overexpressed in tumors and one, SF2/ASF, was shown to be an oncogene. PTB and SRp20 are overexpressed in human ovarian tumors, compared to normal ovarian epithelium, where PTB is either not expressed or expressed at very low levels, and expression of these SFs is associated with malignancy of these tumors. Knockdown of PTB in ovarian tumor cells in vitro by siRNA substantially suppressed tumor cell growth, colony formation, and invasiveness and led to slower tumor growth in mice bearing ovarian tumors. Our results provide proof-of-principle that splicing factors may be a class of novel and unexplored therapeutic targets for cancer treatment, at least PTB in EOC, a disease that has a dismal outcome and for which there are no good therapeutic options, especially for advanced-stage disease. In this proposal, we focus on one splicing factor, PTB, and one tumor type, EOC, and hypothesize that PTB is a druggable therapeutic target in this disease. To test our hypothesis, we propose to develop a cell- based high-throughput screen of small molecule libraries to identify small molecules that interfere with PTB activity and then study whether these identified small molecules are able to inhibit ovarian tumor growth. To this end, we offer three specific aims: (1) Develop and optimize a proprietary cell-based reporter system to monitor the activity of PTB in the cell; (2) Develop and optimize a high throughput screen (HTS) of small molecule libraries, including those containing FDA-approved small molecules as well as extracts from natural sources or compounds generated by chemical synthesis to identify PTB inhibitors; and (3) Validation of effective small molecules on ovarian tumor cell growth in vitro and in vivo. If successful, our approach will validate PTB as a novel therapeutic target and will identify a novel class of small molecule drugs based on the manipulation of alternative splicing for the treatment of ovarian cancer, and possibly other epithelial cancers. PUBLIC HEALTH RELEVANCE: Epithelial ovarian cancer (EOC) strikes more than 25,000 American women annually, and >50% of these women will die from their disease, especially if diagnosed, as is common, with late-stage disease. If successful, the research proposed here will validate targeting of splicing factors and alternative splicing as a novel therapeutic approach to the treatment of ovarian and other cancers. At the end of the project period we would have identified small molecules leading to new drugs for the treatment of these cancers, and this will clearly have a positive impact on public health.