THE ROLE OF TROP2 IN PROSTATE STEM CELL BIOLOGY AND TUMORIGENESIS

描述（由申请人提供）：癌症干细胞具有在其正常组织对应物中发现的功能和分子特征的观察结果提高了正常干细胞是致癌转化的优先和/或必要靶点的可能性，其鉴定可能导致预防和治疗癌症的新策略。Trop 2是一种上皮限制性跨膜蛋白，在许多癌中过表达，具有致癌活性，并且是结肠癌肿瘤发生所需的。在人类和小鼠前列腺中，高Trop 2表达标志着基底干细胞的亚群。最近的实验已经揭示，只有Trop 2 hi群体的人前列腺细胞能够响应于PI 3激酶途径活化而经历有效的转化。有趣的是，Trop 2 hi细胞群在PTEN缺失小鼠模型中肿瘤发生之前在组织学正常的前列腺组织中显著扩增，并且在这些小鼠中出现的癌症也表达高水平的Trop 2。总的来说，这些数据表明Trop 2 hi细胞是转化的靶标，因此Trop 2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，在何种程度上，它实际上是需要在体内的功能，这些过程是未知的，部分原因是缺乏一个适当的动物模型来研究其作用。 我的实验室开始对Trop 2在癌症中的功能感兴趣，因为我们确定了这种蛋白质在结肠癌中的重要作用;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。该探索性R21应用的目的是确定Trop 2在体内前列腺干细胞功能和肿瘤发生中所需的程度。该提议的中心假设是：（1）Trop 2是前列腺中干细胞功能所需的;和（2）Trop 2缺失将抑制体内前列腺肿瘤发生。为了验证这些假设，我们开发了第一个Trop 2基因敲除小鼠品系，并提出了两个具体目标。(1)探讨Trop 2在前列腺干细胞功能中的作用。我们将测量Trop 2无效前列腺组织的再生潜力，并在体内和体外分析其在去势和睾酮诱导的再生后的结构。自最初提交以来，我们已经产生了初步数据，揭示了Trop 2-/-细胞中的前列腺干细胞缺陷。(2)确定Trop 2在小鼠中PTEN缺失介导的前列腺肿瘤发生和转移中的作用。Trop 2和PTEN缺陷型小鼠品系将用于评估Trop 2功能丧失对前列腺中肿瘤发展和转移动力学的影响。我们预测Trop 2缺失将抑制小鼠中PTEN缺失诱导的前列腺肿瘤发生的正常发展。对转化的细胞靶点和由此衍生的肿瘤共有的分子组分的鉴定预期将产生对癌症起始和维持的要求的了解。我们希望最终将这些信息应用于早期检测和治疗的新策略的开发。

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.