Project 1: Roles of wild-type and mutant forms of p53 in cancer cell biology

项目摘要 项目1：野生型和突变型p53在调节肿瘤发生中的相反作用。 野生型P53蛋白被认为是一种主要的肿瘤抑制蛋白。P53位于 众多上游胁迫信号和下游基因调控通路的枢纽 作为一种转录因子发挥作用，其不同的转录靶点介导许多细胞 结果。根据具体情况，这些包括细胞周期、细胞死亡、衰老、 新陈代谢变化和其他有助于保护细胞免受癌症特性影响的物质。 相比之下，越来越多的证据表明，在人类中发现的常见的p53突变形式 肿瘤实际上是导致其恶性的原因之一。野生型和突变型p53 已经证明，每个基因都可以调控超过1000个基因的表达。有趣的是，在许多情况下 突变型P53上调的基因和途径被野生型P53主动抑制。 这是突变型p53获得致癌功能的一条证据 程序是发现突变体P53调节依赖于SREBP-2的甲伐他酸 (MVA)细胞合成胆固醇的途径，这是恶性肿瘤所必需的 在3D培养中生长的乳腺癌细胞的特征。我们现在有证据表明 与洛威实验室合作，野生型p53积极抑制MVA途径 通过一种新的机制，即P53诱导ABCA1胆固醇输出通路被阻断 SREBP-2转录因子的成熟。斯科特·洛的研究表明，P53 Myc/P53缺失的肝肿瘤的发生需要抑制MVA通路。 有趣的是，MVA途径的一个关键副产品，即蛋白质香叶素，是 突变型p53上调MVA途径所必需的，而该副产物的消融起作用 在野生型抑制这一途径中的作用。我们最近还发现了VEGFR2受体 对于促血管生成的血管内皮生长因子配体，作为另一个被突变型p53上调的基因 乳腺癌细胞。VEGFR2 RNA表达的激活涉及突变型P53的协同作用 与SWI/SNF染色质重塑复合体的结合。事实上，突变型p53的调控接近一半 它的靶点包括MVA途径基因，需要SWI/SNF。这个项目的目标是 为了进一步了解突变型p53如何与SREBP2一起调节已知的(MVA) 和VEGFR2)以及预期的新靶基因，以深入了解正反馈 突变型P53与SWI/SNF的关系，以确定P53激活的方式和时间 ABCA1阻断SREBP2蛋白的成熟，以确定哪些香叶基香叶基靶向 在乳腺癌细胞培养中维持生长和恶性所需的，并鉴定 导致依赖MVA通路以获得生存能力的因素。这些实验，将会 可能为癌症的新治疗提供信息，在许多情况下将涉及合作项目 和这个项目的其他成员一起。

Project Summary Project 1: Opposing Roles of Wild-type and Mutant p53 in Regulating Oncogenesis. The wild-type p53 protein is recognized as a major tumor suppressor protein. p53 sits at the hub of numerous upstream stress signaling and downstream gene regulatory pathways and works as a transcription factor whose varied transcriptional targets mediate numerous cellular outcomes. Depending on the context, these include cell cycle, cell death, senescence, metabolic changes and others that serve to protect cells from acquiring cancerous properties. By contrast, evidence continues to mount that the common mutant forms of p53 found in human tumors are actually contributing to their malignant properties. Both wild-type and mutant p53 have been shown to regulate expression over 1000 genes each. Interestingly, in many cases the genes and pathways that mutant p53 upregulates are actively inhibited by wild-type p53. One line of evidence for mutant p53 gain of oncogenic function that was supported by this program was the discovery that mutant p53 regulates the SREBP-2-dependent mevalonic acid (MVA) pathway by which cells synthesize cholesterol and that this is required for the malignant characteristics of breast cancer cells grown in 3D cultures. We now have evidence in collaboration with the Lowe laboratory that wild-type p53 actively represses the MVA pathway by a novel mechanism whereby p53 induces the ABCA1 cholesterol exporter leading to blocked maturation of the SREBP-2 transcription factor. With Scott Lowe we showed that p53 repression of the MVA pathway is required for Myc/p53 null liver tumors to develop. Interestingly, a key byproduct of the MVA pathway, namely protein geranylgeranylation, is required for mutant p53 to upregulate the MVA pathway and ablation of this byproduct plays a role in wild-type repression of this pathway. We also recently discovered VEGFR2, the receptor for the pro-angiogenic VEGF ligand, as another gene that is up-regulated by mutant p53 in breast cancer cells. Activation of VEGFR2 RNA expression involves mutant p53 cooperation with the SWI/SNF chromatin remodeling complex. Indeed, mutant p53 regulation of nearly half of its targets including the MVA pathway genes requires SWI/SNF. The goals of this project are to gain further insight into how mutant p53 works with SREBP2 to regulate both known (MVA and VEGFR2) as well as anticipated new target genes, to gain insight into the positive feedback relationship between mutant p53 and SWI/SNF, to determine how and when p53 activates ABCA1 to block maturation of the SREBP2 protein, to identify which geranylgeranyl targets are required for maintaining growth and malignancy in breast cancer cell cultures, and to identify factors that lead to dependency on the MVA pathway for viability. These experiments, which will potentially inform new treatments for cancer, will in many cases involve collaborative projects with the other members of this program.