Decoding NanogP8 in Tumorigenesis

描述(申请人提供)：肿瘤发生类似于异常胚胎发生。与发育中的器官一样，肿瘤由一系列表型不同的细胞组成，可能含有干细胞样细胞，通常被称为癌症干细胞(CSCs)。尽管CSC的概念仍然存在争议，CSCs的真实分子性质和临床意义仍有待充分阐明，但不可否认的是，恶性肿瘤在人群水平上是不朽的。具有治疗意义的关键生物学问题之一是如何在分子水平上调节癌细胞，尤其是肿瘤干细胞，使其具有自我维持(不朽)的致瘤潜能，即自我更新特性。值得注意的是，恶性细胞与胚胎干细胞(ESCs)有相似的基因表达谱，后者表达几个自我更新和多能性的核心调控因子，包括位于12号染色体上的同源区域转录因子Nanog(也称为Nanog1)。我们观察到，人类前列腺癌和其他癌细胞不表达Nanog1，而是表达位于15号染色体上的逆转座的Nanog1同源物，称为NanogP8。敲除NanogP8显著抑制了PCa以及乳腺和结肠癌细胞的CSC特性和肿瘤再生。相比之下，NanogP8的过表达足以赋予CSC特性，增强肿瘤再生，并显著促进抗去势的PCa或CRPC的发展。我们最近的全基因组芯片-序列实验发现了不同的NanogP8 DNA结合图谱。此外，新产生的NanogP8转基因动物会在靶器官出现增生性病变。综上所述，我们的主要假设是：1)NanogP8具有促肿瘤活性；2)NanogP8通过独特的信号通路调节CSC的自我更新，从而促进肿瘤的发展；以及3)NanogP8在CRPC的发展中起因果作用。目前的项目主要是在主成分分析中检验这些假设，具体目标如下。1)验证NanogP8参与CRPC发生的假设；2)阐明NanogP8的细胞和分子作用机制；3)利用新型转基因动物模型探讨NanogP8的促肿瘤作用。影响：本文提出的目标的实现将极大地促进我们对NanogP8如何调节CSCs永生化的理解，并有助于肿瘤的发展和CRPC。它还将促进专门针对PCSCs的基于机制的疗法的开发。

DESCRIPTION (provided by applicant): Tumorigenesis resembles abnormal embryogenesis. Like developing organs, tumors comprise a spectrum of phenotypically heterogeneous cells and may harbor stem cell-like cells commonly referred to as cancer stem cells (CSCs). Although the CSC concept is still debated and the true molecular nature and clinical significance of CSCs remain to be fully elucidated, it is undeniable that malignant tumors are immortal at the population level. One of the key unanswered biological questions of therapeutic implication is how cancer cells in general and CSCs in particular are regulated at the molecular level with respect to their self-perpetuating (immortal) tumorigenic potential, i.e., self-renewal properties. Remarkably, malignant cells share a similar gene expression profile with embryonic SC (ESCs), which express several core regulators of self-renewal and pluripotency including Nanog (also called Nanog1), a homeodomain transcription factor located on chromosome 12. We have observed that human PCa and other cancer cells do NOT express Nanog1 but rather express a retrotransposed Nanog1 homolog, called NanogP8, located on chromosome 15. Knocking down NanogP8 significantly inhibits the CSC properties in vitro and tumor regeneration of PCa and breast and colon cancer cells. In contrast, NanogP8 overexpression is sufficient to confer CSC properties, enhances tumor regeneration, and, significantly, promotes development of castration-resistant PCa or CRPC. Our recent whole-genome ChIP-Seq experiment has uncovered distinct NanogP8 DNA-binding profiles. Furthermore, newly generated NanogP8 transgenic animals develop hyperplastic lesions in the target organs. These observations, taken together, lead to our overarching hypotheses that 1) NanogP8 possesses protumorigenic activity; 2) NanogP8 promotes tumor development by regulating CSC self-renewal via unique signaling pathways; and 3) NanogP8 plays a causal role in the development of CRPC. The current project tests these hypotheses, mainly, in PCa with the following three Specific Aims. 1) To test the hypothesis that NanogP8 is causally involved in the development of CRPC; 2) To elucidate the cellular and molecular mechanisms of action of NanogP8; and 3) To explore the protumorigenic roles of NanogP8 using novel transgenic animal models. Impact: Accomplishment of the goals proposed herein should greatly advance our understanding of how NanogP8 regulates the immortality of CSCs and contribute to tumor development and CRPC. It will also facilitate development of mechanism-based therapeutics that specifically targets PCSCs.