p63 Signaling in Epithelial Cell Growth and Cancer

描述（申请人提供）：提出的研究的目标是解决p53家族成员p63在上皮细胞信号传导和功能中的作用，p63在包括表皮、口腔粘膜、食管和膀胱的几个分层上皮组织的基底层中表达，以及在几个腺体结构如支气管、乳腺和前列腺中表达，p63缺陷小鼠和具有p63种系突变的人显示严重的上皮相关缺陷。p63基因编码六个剪接变体，具有几种预测的生化活性。在成人中，一种p63同种型deltaNp 63 α的表达在其表达的组织中的上皮细胞的基底亚群中最高，并且在鳞状细胞癌中经常过表达。 基于我们最近的发现，deltaNp 63 α：（i）可以作为转录抑制因子发挥作用，（ii）受生长刺激和抑制信号的调节，（iii）缺失可以导致上皮细胞衰老，我们提出了以下相关假设。DeltaNp 63 α通过生长刺激和抑制信号传导被差异磷酸化，并通过选择靶基因的转录调节在维持表皮储备细胞群的增殖状态中发挥作用，所述表皮储备细胞群将更分化的细胞与基质分离。我们将通过分析deltaNp 63 α磷酸化，鉴定deltaNp 63 α在体内结合和调节的新靶基因，并确定选择的p63靶基因在上皮细胞自我更新中的作用来测试这些假设。对于我们的研究，我们将主要使用原代正常人表皮角质形成细胞和乳腺肌上皮细胞。新的技术和试剂将通过以下具体目的来测试假设：（i）鉴定deltaNp 63 α在体内结合和调节的靶基因;（ii）确定选择的deltaNp 63 α靶基因在决定增殖、衰老、分化和应激条件下的细胞结果中的作用;和（iii）分析deltaNp 63 α磷酸化及其在调节deltaNp 63 α蛋白水平和活性中的作用。在几种人类肿瘤类型中deltaNp 63 α过表达的频率、p63发生生殖系突变的人类发育障碍以及在人类癌细胞中调节deltaNp 63 α信号传导可能诱导生长停滞或凋亡的希望，强调了理解deltaNp 63 α调节和功能的重要性。

DESCRIPTION (provided by applicant): The goal of the proposed studies is to address the role of one p53 family member, p63, in epithelial cell signaling and function, p63 is expressed in the basal layer of several stratified epithelial tissues including the epidermis, oral mucosa, esophagus, and bladder, as well as in several glandular structures such as bronchi, breast and prostate, p63-deficient mice and humans with p63 germline mutations display severe epithelium-related defects. The p63 gene encodes six splice variants with several predicted biochemical activities. In adults, expression of one p63 isoform, deltaNp63alpha is highest in the basal subpopulation of epithelial cells in tissues in which it is expressed and is frequently overexpressed in squamous cell carcinomas. Based on our recent discoveries that deltaNp63alpha: (i) can function as a transcriptional repressor, (ii) is regulated by growth stimulatory and inhibitory signaling, and (iii) loss can lead to epithelial cell senescence, we put forth the following interrelated hypotheses. DeltaNp63alpha is differentially phosphorylated by growth stimulatory and inhibitory signaling, and through transcriptional regulation of select target genes plays a role in maintenance of the proliferative state of epidermal reserve cell populations that separate the more differentiated cells from the stroma. We will test these hypotheses by analyzing deltaNp63alpha phosphorylation, identifying novel target genes that deltaNp63alpha binds and regulates in vivo, and determining the role of select p63 target genes in epithelial cell self-renewal. For our studies, we will predominantly use primary, normal, human epidermal keratinocytes and breast myoepithelial cells. New technologies and reagents will be exploited to test the hypotheses through the following Specific Aims: (i) To identify target genes that deltaNp63alpha binds and regulates in vivo; (ii) To determine the role of select deltaNp63alpha target genes in dictating cellular outcome under conditions of proliferation, senescence, differentiation, and stress; and (iii) To analyze deltaNp63alpha phosphorylation and the role it plays in regulating deltaNp63alpha protein levels and activity. The importance of understanding deltaNp63alpha regulation and function is underscored by the frequency of deltaNp63alpha overexpression in several human tumor types, the occurrence of human developmental disorders with germline mutations in p63, and the hope that modulating deltaNp63alpha signaling in human cancer cells may induce growth arrest or apoptosis.