Targeting Gain-of-Function p53 Missense Mutants

描述(申请人提供)：三阴性乳腺癌(TNBC)是一个严重的健康问题。TNBC占所有乳腺癌的10%-20%，比其他类型的疾病更具侵袭性，平均诊断年龄更低，复发率更高，生存时间更短。TNBC带来的最大挑战之一是缺乏与该疾病相关的共同致癌‘驱动因素’，从而限制了靶向治疗的战略。目前，还没有有效的靶向疗法来治疗这种疾病，不像其他由雌激素受体和HER2驱动的乳腺癌，在这些类型的乳腺癌中，他莫昔芬和曲妥珠单抗的治疗对生存率产生了重大影响。对大量TNBC肿瘤的分析发现了各种各样的低频突变，我们的实验室最近发表的一项研究表明，这种疾病至少有六种不同的分子亚型。我们研究的长期目标是确定可以作为TNBC治疗靶点的途径。大多数TNBC病例的一个共同特征是编码p53肿瘤抑制因子(TP53)的基因发生错义突变，导致产生具有单一氨基酸差异的无功能版本的蛋白质。最近的研究发现，这些突变蛋白中的一些可以增强细胞的增殖、迁移和对化疗药物的抵抗力，从而具有特殊的“功能获得”特性。此外，我们的实验室有初步数据显示，在shRNA表达后，某些突变型p53细胞的生长受到抑制，这降低了P53RNA和蛋白质的水平，证实了之前发表的数据。基于这些集体数据，我们假设具有P53错义突变的肿瘤存在突变的P53附加状态，确定这种状态的分子基础将为治疗开发提供靶点。按顺序 为了验证这一假说，我们提出了三个目标：1)确定导致突变型p53适应状态的机制，2)识别其被敲除的基因特异性地抑制P53突变型TNBC细胞，以及3)通过临床肿瘤样本的差异基因表达分析来发展错义突变型特异性分子特征。我们将利用现代技术，包括转录分析和对广泛的细胞系和不同的p53错义突变进行全基因组基因筛查。此外，我们将整合不断增长的转录和基因组数据集，这些数据集来自公共资源，如癌症基因组图谱，以便在患者肿瘤样本的背景下确定与特定的p53错义突变相关的分子特征。在这个过程中，我们将增加我们对肿瘤如何适应突变的p53的理解，并测试我们的假设，即以这种适应状态为靶点是一种特异性抑制癌细胞的方法。我们的研究结果将有可能转化为几乎所有形式的人类癌症，并可能有助于对抗TNBC以及其他具有高频p53突变的疾病，如卵巢癌和肺鳞状细胞癌，这些疾病尚未找到有效的靶向治疗。

DESCRIPTION (provided by applicant): Triple-negative breast cancer (TNBC) is a serious health concern. Representing 10-20% of all breast cancers, TNBC is more aggressive than other forms of the disease, with a younger average age of diagnosis, increased rate of relapse, and decreased survival. One of the greatest challenges presented by TNBC is the lack of common oncogenic 'drivers' associated with the disease, thus limiting strategies for targeted therapeutics. Currently, there are no effective targeted therapies available to treat the disease, unlike other forms of breast cancer driven by estrogen receptor and HER2 in which treatment with tamoxifen and trastuzumab has made a substantial impact on survival. Profiling of a large number of TNBC tumors has identified a wide variety of low- frequency mutations, and our laboratory recently published a study showing that there are at least six distinct molecular subtypes of the disease. The long-term goals of our research are to identify pathways that can be therapeutically targeted in TNBC. One feature shared by a majority of TNBC cases is missense mutations in the gene encoding the p53 tumor suppressor (TP53), which result in the production of a non-functional version of the protein with a single amino acid difference. Recent studies have identified special "gain of function" properties conferred by some of these mutant proteins that enhance cell proliferation, migration and resistance to chemotherapeutic agents. Further, our laboratory has preliminary data showing growth inhibition of certain mutant-p53 cells after shRNA expression that decreases the levels of p53 RNA and protein, confirming previously published data. Based on these collective data, we hypothesize that tumors with p53 missense mutations exist in a mutant p53-adpated state, and determining the molecular underpinnings of this state will provide insight into targets for therapeutic development. In order to test this hypothesis, we propose three aims: 1) to determine mechanisms contributing to the mutant p53-adapted state, 2) to identify genes whose knockdown specifically inhibits p53-mutant TNBC cells, and 3) to develop missense mutant- specific molecular signatures through differential gene expression analysis of clinical tumor samples. We will leverage modern techniques including transcriptional analysis and whole-genome genetic screening across a wide array of cell lines and distinct p53 missense mutants. In addition, we will incorporate an ever-growing body of transcriptional and genomic datasets from publically available resources such as The Cancer Genome Atlas in order to identify molecular features associated with specific p53 missense mutants in the context of patient tumor samples. In the process, we will increase our understanding of how tumors adapt to mutant p53 and test our hypothesis that targeting this adapted state is a way to specifically inhibit cancer cells. The results generated from our studies will have potential translation to nearly every form of human cancer, and could help in the fight against TNBC as well as other diseases with high-frequency p53 mutation, such as ovarian cancer and lung squamous cell carcinoma, for which no effective targeted therapy has yet been found.