Functional genomics approach to evaluate mechanisms of mutant p53 gain-of-function phenotypes

项目概要/摘要 三阴性乳腺癌（TNBC）是一种侵袭性乳腺癌亚型，缺乏传统的临床治疗方法。 目标;因此，细胞毒性化疗是目前的护理标准。靶向治疗的发展 由于分子异质性和缺乏治疗靶向的，高频率的， “司机”的改变TNBC病例中最统一的特征是~80%的肿瘤中存在突变， 抑制基因TP 53。p53的突变通常是错义的，并已被提出导致获得性突变。 功能（GOF）活性导致新的致癌表型。尽管这种机制的基础 GOF活性尚不清楚，TP 53的改变与染色体数目增加高度相关。 不稳定性（CIN）和非整倍体的发展，并且与代谢失调有关。 为了研究p53 GOF突变蛋白，我们实验室开发了两个同基因细胞系模型（非转化的 乳腺上皮细胞和TNBC细胞系）。模型包括 表达两种常见“热点突变体”p53蛋白（R175 H和R273 H）的克隆细胞系，野生型（WT） 蛋白，或无p53蛋白（p53）。这组细胞系允许研究各种形式的p53， 由内源性基因启动子表达和调节，而没有由 异位和不受调节的过度表达。此外，这些模型提供了一个独特的机会，既解剖 新的和评估提出的GOF机制和表型源于功能性（LOF）p53的丢失 和/或伴随获得突变型p53蛋白表达。我们已经证明，我们的同基因细胞系与 突变型p53具有更高水平的CIN、非整倍体的发展和代谢失调。此外，本发明还 我们已经发现突变蛋白的稳定化与非整倍性的发展显著相关。 在目标1中，我将部署生物化学技术，并分析由以下数据生成的一系列基因组学数据集： 我们的细胞系模型来评估突变型p53和p73相互作用与CIN之间的关系。In Aim 2 I 将使用生物化学技术和靶向代谢组学来研究非整倍体的发展是如何导致 突变型p53稳定和代谢改变的GOF表型。通过这些目标，我将测试 假设突变p53 LOF和/或GOF机制发现和剖析， 与肿瘤细胞中的非整倍体相关的细胞状态，将导致识别新的前体， TNBC的临床目标。我预计对新机制的剖析以及对新机制的评估 突变型p53 GOF表型的拟议机制的可重复性将改善目前的 了解突变型p53在肿瘤发生中的作用。从我们的研究产生的结果有 临床转化的潜力，不仅在TNBC中（对靶向治疗的需求至关重要），而且 在其他类型的人类癌症中有高频率的p53突变。

Project Summary/Abstract Triple-negative breast cancer (TNBC) is an aggressive subtype of breast cancer that lacks traditional clinical targets; as a result, cytotoxic chemotherapy is the current standard of care. Development of targeted therapies for TNBC is challenging due to molecular heterogeneity and a lack of therapeutically targetable, high-frequency “driver” alterations. The most unifying feature across TNBC cases is that ~80% harbor a mutation in the tumor suppressor gene TP53. Mutations in p53 are commonly missense and have been proposed to result in gain-of- function (GOF) activity leading to novel oncogenic phenotypes. Although the mechanistic underpinnings of this GOF activity are not understood, alterations in TP53 are highly correlated with increased chromosomal instability (CIN) and the development of aneuploidy, and have been associated with dysregulated metabolism. To study p53 GOF mutant proteins, our lab developed two isogenic cell line models (non-transformed mammary epithelial and TNBC cell lines) using CRISPR/Cas-mediated genome editing. The models include clonal cell lines expressing two common “hotspot mutant” p53 proteins (R175H and R273H), wild-type (WT) protein, or no p53 protein (Null). This panel of cell lines allows for the study of various forms of p53, all expressed and regulated by the endogenous gene promoter and without the confounding effects caused by ectopic and unregulated overexpression. Additionally, these models afford a unique opportunity to both dissect novel and evaluate proposed GOF mechanisms and phenotypes that stem from loss of functional (LOF) p53 and/or concomitant gain of mutant p53 protein expression. We have shown that our isogenic cell lines with mutant p53 have higher levels of CIN, development of aneuploidy and dysregulated metabolism. Additionally, we have found that stabilization of mutant protein significantly correlates with the development of aneuploidy. In Aim 1 I will deploy biochemical techniques and analysis of an array of genomics data sets generated from our cell line models to evaluate the relationship between mutant p53 and p73 interactions and CIN. In Aim 2 I will use biochemical techniques and targeted metabolomics to study how development of aneuploidy underlies the GOF phenotypes of mutant p53 stabilization and altered metabolism. Through these aims I will test the hypothesis that discovery and dissection of mutant p53 LOF and/or GOF mechanisms, which generate cellular states associated with aneuploidy in tumor cells, will lead to the identification of novel pre- clinical targets for TNBC. I anticipate that the dissection of novel mechanisms as well as the evaluation of the reproducibility of proposed mechanisms for mutant p53 GOF phenotypes will improve the current understanding of the role mutant p53 in tumorigenesis. The results generated from our studies have the potential for clinical translation, not only in TNBC (for which the need for a targeted therapy is critical), but also in other types of human cancer that have high-frequency p53 mutation.