p63 and p73 Signaling in Cell Growth and Cancer

描述（由申请人提供）：尽管p53在肿瘤抑制中的关键作用尚未受到挑战，但其家族成员p63和p73在正常细胞功能和肿瘤发生中的作用远未确定。p53蛋白家族的结构相似性和功能将它们以类似的信号传导途径（协作和拮抗相互作用）连接起来;然而，体内模型表明p63和p73在p53独立的发育和分化过程中发挥作用。特别是，p63基因缺失的小鼠缺乏表皮和相关结构，如乳腺和前列腺。有趣的是，p63在几种上皮组织如皮肤、乳腺和前列腺的基底层中表达，并且在许多鳞状和基底样癌中过表达。有证据表明，p63可能部分通过与p73相互作用而在肿瘤中发挥作用，p73在许多人类肿瘤中也过表达。这些研究的目的是确定p63和p73在细胞代谢和存活以及上皮-间充质串扰和转化中的作用，并发现这些作用在肿瘤发生过程中是如何失调的。 通过综合染色质免疫沉淀和微阵列数据集的生成和整合，我们鉴定了许多新的p63和p73靶基因。基于我们的研究结果，我们提出了以下相互关联的假设：（i）p63和p73调节参与细胞代谢和存活以及上皮-间充质串扰和转化的独特或共享靶基因的转录;和（ii）适当p63和p73活性的丧失将导致细胞存活和功能改变，从而导致发育异常或肿瘤发生，这取决于功能障碍的生物学时间点。这些假设将通过以下具体目的进行检验：（1）分析选择p63和p73独特或协同调控的新靶基因。我们将使用器官型模型系统确定这些靶基因在p63和p73信号传导下游生物学相关终点中的作用;（2）分析p63和p73蛋白复合物以及一种新鉴定的与这些家族成员相互作用的蛋白质;（3）分析p73有条件的组织特异性敲除小鼠。将在器官和代谢功能以及对应激的反应方面表征小鼠。将研究组织特异性敲除p63、p73和p53（单独或组合）在乳腺中的作用，以确定家族成员在成人组织功能中的单独或协调作用以及对肿瘤发生的易感性。 理解p63和p73调控和功能的重要性通过人类肿瘤中p53家族的失调以及对癌症中p63和p73信号传导轴的机制理解将转化为癌症患者的治疗益处的期望而得到强调。 公共卫生相关性：虽然p53已被广泛表征为肿瘤抑制因子，但更难以确定其家族成员p63和p73是否发挥类似作用。在拟议的研究中，我们将采用基因工程细胞和小鼠模型系统来确定p63和p73在细胞代谢和存活以及上皮-间充质串扰和转换中的作用，并发现这些作用在肿瘤发生过程中是如何失调的。必须破译这些蛋白质在正常细胞功能和肿瘤发生期间的作用，以设计更有效的抗癌疗法，其将靶向具有缺陷的p53家族信号传导轴的大多数人类肿瘤。

DESCRIPTION (provided by applicant): Although the pivotal role of p53 in tumor suppression remains unchallenged, the role of its family members, p63 and p73 in normal cell function and tumorigenesis is far from certain. Structural similarities and functions of the p53 family of proteins connect them in similar signaling pathways, in both collaborative and antagonistic interactions; however, in vivo models suggest a role for both p63 and p73 in p53-independent developmental and differentiation processes. In particular, p63-null mice lack an epidermis and related structures such as mammary and prostate glands. Interestingly, p63 is expressed in the basal layer of several epithelial tissues such as skin, breast and prostate, and is overexpressed in many squamous and basal-like carcinomas. Evidence suggests that p63 may function in tumors in part through interaction with p73, which is also overexpressed in many human tumors. The goal of the proposed studies is to determine the roles of p63 and p73 in cell metabolism and survival as well as epithelial-mesenchymal crosstalk and transition, and to discover how these roles are deregulated during tumorigenesis. Through generation and integration of comprehensive chromatin immunoprecipitation and microarray data sets, we identified numerous novel p63 and p73 target genes. Based on our findings, we propose the following interrelated hypotheses: (i) p63 and p73 regulate the transcription of unique or shared target genes involved in cell metabolism and survival as well as epithelial-mesenchymal cross-talk and transition; and, (ii) loss of proper p63 and p73 activity will lead to altered cell survival and function resulting in developmental abnormalities or tumorigenesis, depending on the biological time point of dysfunction. These hypotheses will be tested through the following Specific Aims: (1) To analyze select novel target genes uniquely or coordinately regulated by p63 and p73. We will determine the role of these target genes in biologically relevant endpoints downstream of p63 and p73 signaling using organotypic model systems; (2) To analyze p63 and p73 protein complexes and a newly identified protein that interacts with these family members; and (3) To analyze mice with conditional, tissue-specific knock-out of p73. The mice will be characterized in terms of organ and metabolic function and response to stress. The effect of tissue-specific knockout of p63, p73, and p53, alone or in combination, in the mammary gland will be studied to determine the separate or coordinate roles of the family members in adult tissue function, and susceptibility to tumorigenesis. The importance of understanding p63 and p73 regulation and function is underscored by the deregulation of the p53 family in human tumors and the expectation that a mechanistic understanding of the p63 and p73 signaling axes in cancer will translate to therapeutic benefit for cancer patients. PUBLIC HEALTH RELEVANCE: While p53 has been extensively characterized as a tumor suppressor, it has been more difficult to determine if its family members, p63 and p73 play a similar role. In the proposed studies, we will employ genetically engineered cell and mouse model systems to determine the roles of p63 and p73 in cell metabolism and survival as well as epithelial-mesenchymal crosstalk and transition, and to discover how these roles are deregulated during tumorigenesis. It is essential to decipher the role of these proteins in both normal cell function and during tumorigenesis in order to design more effective anti- cancer therapies that will target the majority of human tumors that have a defective p53 family signaling axis.