Targeting Gain-of-Function p53 Missense Mutants

描述（由申请人提供）：三阴性乳腺癌（TNBC）是一种严重的健康问题。TNBC占所有乳腺癌的10-20%，比其他形式的疾病更具侵袭性，平均诊断年龄更年轻，复发率增加，生存率降低。TNBC带来的最大挑战之一是缺乏与该疾病相关的常见致癌“驱动因素”，从而限制了靶向治疗策略。目前，没有有效的靶向治疗方法可用于治疗该疾病，不像其他形式的由雌激素受体和HER2驱动的乳腺癌，使用他莫昔芬和曲妥珠单抗治疗对生存产生了实质性影响。对大量TNBC肿瘤的分析已经确定了多种低频突变，我们的实验室最近发表的一项研究表明，该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治疗TNBC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，导致产生具有单个氨基酸差异的无功能蛋白。最近的研究已经确定了一些突变蛋白所赋予的特殊“功能增益”特性，这些特性增强了细胞增殖、迁移和对化疗药物的耐药性。此外，我们实验室的初步数据显示，shRNA表达后某些突变型p53细胞的生长受到抑制，降低了p53 RNA和蛋白质的水平，证实了先前发表的数据。基于这些集体数据，我们假设p53错义突变的肿瘤存在于p53突变适应状态，并确定这种状态的分子基础将为治疗开发的靶点提供见解。为了

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.