p63 and p73 Signaling in Cell Growth and Cancer

尽管p53在肿瘤抑制中的关键作用仍然是毋庸置疑的，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还远未确定。p53家族蛋白的结构相似性和功能将它们连接在相似的信号通路中，在协同和拮抗相互作用中；然而，体内模型表明p63和p73在不依赖于p53的发育和分化过程中都有作用。特别是，p63缺失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表达，并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相互作用在肿瘤中起作用，p73在许多人类肿瘤中也过表达。这些研究的目标是确定p63和p73在细胞代谢和存活以及上皮-间质串音和转化中的作用，并发现这些作用在肿瘤发生过程中是如何被解除调控的。通过生成和整合全面的染色质免疫沉淀和微阵列数据集，我们鉴定了许多新的p63和p73靶基因。基于我们的研究结果，我们提出了以下相关假设：(i) p63和p73调节参与细胞代谢和存活以及上皮-间质相互作用和转化的独特或共享靶基因的转录；（ii） p63和p73活性的缺失将导致细胞存活和功能的改变，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验证：(1)分析选择p63和p73单独或协调调节的新靶基因。我们将使用器官型模型系统确定这些靶基因在p63和p73信号传导下游的生物学相关端点中的作用；(2)分析p63和p73蛋白复合物以及新发现的与这些家族成员相互作用的蛋白；(3)分析p73有条件、组织特异性敲除的小鼠。这些小鼠将在器官和代谢功能以及对应激的反应方面进行表征。将研究乳腺中p63、p73和p53的组织特异性敲除，单独或联合的影响，以确定家族成员在成人组织功能和肿瘤发生易感性中的单独或协调作用。了解p63和p73调控和功能的重要性被人类肿瘤中p53家族的解除管制以及对癌症中p63和p73信号轴的机制理解将转化为癌症患者的治疗益处的期望所强调。

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.