Decoding NanogP8 in Tumorigenesis

描述（由申请人提供）： 肿瘤发生类似于异常胚胎发生。与发育中的器官一样，肿瘤包含一系列表型异质性细胞，并且可能含有通常称为癌症干细胞（CSC）的干细胞样细胞。尽管CSC的概念仍有争议，CSC的真正分子本质和临床意义仍有待充分阐明，但不可否认的是，恶性肿瘤在群体水平上是不朽的。具有治疗意义的关键的未回答的生物学问题之一是癌细胞，特别是CSC，如何在分子水平上就其自我永存（永生）的致瘤潜力进行调节，即，自我更新的特性。值得注意的是，恶性细胞与胚胎干细胞（ESC）有着相似的基因表达谱，胚胎干细胞表达几种自我更新和多能性的核心调节因子，包括Nanog（也称为Nanog 1），一种位于12号染色体上的同源结构域转录因子。我们已经观察到，人类前列腺癌和其他癌细胞不表达Nanog 1，而是表达位于15号染色体上的逆转录转座Nanog 1同源物，称为NanogP 8。敲低NanogP 8显著抑制体外CSC特性以及PCa和乳腺癌和结肠癌细胞的肿瘤再生。相比之下，NanogP 8过表达足以赋予CSC特性，增强肿瘤再生，并显著促进去势抵抗性PCa或CRPC的发展。我们最近的全基因组ChIP-Seq实验揭示了不同的NanogP 8 DNA结合谱。此外，新产生的NanogP 8转基因动物在靶器官中产生增生性病变。这些观察结果结合在一起，导致我们的总体假设：1）NanogP 8具有促肿瘤活性; 2）NanogP 8通过独特的信号通路调节CSC自我更新来促进肿瘤发展; 3）NanogP 8在CRPC的发展中起着因果作用。目前的项目测试这些假设，主要是在PCa与以下三个具体目标。 1)验证NanogP 8与CRPC的发生有因果关系的假设; 2）阐明NanogP 8的细胞和分子作用机制; 3）使用新型转基因动物模型探索NanogP 8的促肿瘤作用。影响：本文提出的目标的实现将大大促进我们对NanogP 8如何调节CSC的永生性并有助于肿瘤发展和CRPC的理解。它还将促进特异性靶向PCSC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.