THE ROLE OF TROP2 IN PROSTATE STEM CELL BIOLOGY AND TUMORIGENESIS

描述(申请人提供)：观察到癌症干细胞具有在正常组织中发现的功能和分子特征，这增加了正常干细胞是致癌转化的优先和/或必要靶点的可能性，其识别可能导致癌症预防和治疗的新策略。Trop2是一种上皮限制性跨膜蛋白，在许多肿瘤中过表达，具有致癌活性，是结肠癌发生所必需的。在人类和小鼠的前列腺中，高表达的Trop2标志着基本干细胞的一个亚群。最近的实验表明，只有人前列腺细胞的Trop2hi群体才有能力进行有效的转化，以响应PI3激酶途径的激活。有趣的是，在PTEN缺失的小鼠模型肿瘤发生之前，在组织学上正常的前列腺组织中，Trop2hi细胞群显著扩大，并且在这些小鼠中出现的癌症也表达高水平的Trop2。总而言之，这些数据表明Trop2hi细胞是转化的目标，因此Trop2可能在前列腺干细胞和肿瘤生物学中发挥重要的功能作用。然而，这些过程在体内实际需要多少功能尚不清楚，部分原因是缺乏合适的动物模型来研究它的作用。我的实验室在确定Trop2蛋白在结肠癌中的重要作用后，开始对该蛋白在癌症中的功能感兴趣；因此，了解它在肿瘤生物学中的作用是我们的长期目标之一，S。R21的这一探索性应用的目的是确定体内前列腺干细胞功能和肿瘤发生所需的Trop2的程度。这一提议的中心假设是：(1)Trop2是前列腺干细胞功能所必需的；(2)Trop2缺失将抑制体内前列腺癌的发生。为了验证这些假设，我们开发了第一个Trop2基因敲除小鼠品系，并提出了两个特定的目标。(1)探讨Trop2在前列腺干细胞功能中的作用。我们将测量Trop2缺失的前列腺组织以及体内和体外的再生潜力，并分析其在去势和睾酮诱导再生后的结构。自最初提交以来，我们已经产生了初步数据，揭示了Trop2-/-细胞中的前列腺干细胞缺陷。(2)探讨Trop2在PTEN缺失介导的小鼠前列腺癌发生和转移中的作用。Trop2和PTEN缺失的小鼠品系将被用来评估Trop2功能丧失对前列腺肿瘤发展和转移动力学的影响。我们预测，Trop2缺失将抑制PTEN缺失诱导的小鼠前列腺肿瘤的正常发展。对细胞转化靶点和由此衍生的肿瘤共有的分子成分的鉴定有望对癌症的启动和维持的要求产生深刻的见解。我们希望最终将这些信息应用于小说策略的制定，以便及早发现和治疗。 公共卫生相关性：癌症生物学中的一个主要问题是非恶性上皮的常驻组织干细胞如何受到致癌信号的影响和影响。这项研究将探讨前列腺干细胞成分的失调可能会影响体内的成瘤能力。这也将为进一步的研究提供基础，旨在阐明肿瘤发生的新的分子要求，其靶向前列腺癌可能被证明是有益的治疗。

DESCRIPTION (provided by applicant): The observation that cancer stem cells possess functional and molecular features found in their normal tissue counterparts has raised the possibility that normal stem cells are preferential and/or requisite targets for oncogenic transformation whose identification could lead to novel strategies for the prevention and treatment of cancer. Trop2 is an epithelial-restricted transmembrane protein that is overexpressed in numerous carcinomas, has oncogenic activity, and is required for colon cancer tumorigenesis. In both the human and mouse prostate, high Trop2 expression marks a sub-population of basal stem cells. Recent experiments have revealed that only the Trop2hi population of human prostate cells is competent to undergo efficient transformation in response to PI3 kinase pathway activation. Interestingly, the Trop2hi cell population is dramatically expanded in histologically normal prostatic tissue prior to the onset of tumorigenesis in the PTEN null mouse model, and the cancers that arise in these mice also express high levels of Trop2. Collectively, these data suggest that Trop2hi cells are targets for transformation and thus Trop2 is likely to play an important functional role in prostate stem cell and tumor biology. However, the extent to which it is actually functionally required in vivo for these processes is unknown in part because of the lack of an appropriate animal model with which to study its role. My laboratory became interested in the function of Trop2 in cancer after we identified an essential role for this protein in colon cancer; therefore understanding its role in tumor biology s one of our long-term goals. The objective of this exploratory R21 application is to determine the extent to which Trop2 is required for prostate stem cell function and tumorigenesis in vivo. The central hypotheses of this proposal are: (1) that Trop2 is required for stem cell function in the prostate: and (2) that Trop2 deletion will suppress prostate tumorigenesis in vivo. To test these hypotheses, we have developed the first Trop2 knockout mouse strain and we propose two specific aims. (1) To evaluate the role of Trop2 in prostate stem cell function. We will measure the regenerative potential of Trop2 null prostate tissue and in vivo and ex vivo and analyze its structure after castration and testosterone-induced regrowth. Since the original submission, we have generated preliminary data revealing a prostate stem cell defect in Trop2-/- cells. (2) To determine the role of Trop2 in PTEN-loss mediated prostate tumorigenesis and metastasis in the mouse. Trop2- and PTEN-deficient mouse strain will be used to evaluate the effects of Trop2 loss of function on the kinetics of tumor development and metastasis in the prostate. We predict that Trop2 deletion will suppress the normal development of PTEN-loss induced prostate tumorigenesis in mice. The identification of molecular components common to the cellular targets of transformation and the tumors derived thereof is expected to produce insights into the requirements for cancer initiation and maintenance. We hope to ultimately apply this information to the development of novels strategies for early detection and treatment. PUBLIC HEALTH RELEVANCE: A major question in cancer biology is how resident tissue stem cells of the non-malignant epithelia are affected by and affect oncogenic signaling. This study will address the possibility that dysregulation of prostate stem cell composition can influence tumorigenic competence in vivo. It will also provide the foundation for further studies aimed at the elucidation of novel molecular requirements for tumorigenesis, whose targeting in prostate cancer may prove to be therapeutically beneficial.