Defining and characterizing microenvironmental drivers of disseminated tumor cell dormancy in brain

项目摘要 脑转移的出现时间晚于其他部位的转移。一旦他们这样做了，他们就会迅速衰弱， 致命的。脑转移瘤出现所需的时间表明，这涉及到休眠阶段。这 这一观点得到了临床和实验数据的支持。事实上，我们自己的初步数据显示，乳房 癌细胞一旦进入大脑就进入休眠状态，而从这种状态出来是速度限制的步骤 转移的可能性。这些数据表明，靶向潜伏的播散性肿瘤细胞(DTC)是一种合乎逻辑的方法 预防脑转移的方法。然而，尽管人们对休眠机制的了解越来越多， 在常见的转移部位，如肺和骨髓，对DCs是如何被驱动进入 大脑中的休眠状态尚未发育。这项提案的首要目标是解决这一问题。我们 将为大脑微环境如何驱动DTC进入休眠状态制定一个基本框架， 来自临床标本的支持，这样我们就可以利用这一理解来进行治疗，使DTC 无限期地休眠。 我们最近的研究发现，休眠的DTC占据了大脑的血管壁龛，在那里 血管周围的星形胶质细胞抑制它们的生长。我们怀疑星形细胞对脑实质的贡献 基底膜负责抑制DTC，这些作用汇聚在一个 常见受体：营养不良多聚糖。因此，我们的假设是：(1)星形细胞基底膜是一种 DTC休眠的关键驱动因素，以及(Ii)Dstroglan功能必须保持完整，DTC才能解释这些 信号。我们将通过两个具体目标来检验这些假设： 目的1.确定星形胶质细胞基底膜是否促进和维持DTC休眠。 目的2.阐明Ddystrocan介导的信号轴对DTC在脑内静止的影响。 为了实现这些目标，我们动用了一切相关资源。这些资源涵盖：(I) 长期活体成像以确定DTC相关星形胶质细胞消融后DTC的命运；(Ii) 转基因小鼠去除星形胶质细胞基底膜对DTC影响的实验研究 (Iii)罕见的临床标本以确定星形胶质细胞和星形胶质细胞基底膜是否也是如此。 与人类中处于休眠状态的DTC有关；以及(Iv)一系列突变、过度和低表达的构建体 解决营养不良糖链是如何由外而内驱动DTC静止的。 这项工作的意义和创新之处在于识别了大脑中的第一个休眠驱动因素， 最终解开营养不良蛋白聚糖驱动的信号，从而影响播散性乳腺肿瘤细胞的静止。这 这项工作将为作为脑转移预防药物的营养不良多糖功能激动剂奠定基础 预防。

Project Summary Brain metastases arise later than metastases at other sites. Once they do, they are rapidly debilitating and lethal. The time it takes for brain metastases to emerge suggests that a dormancy phase is involved. This notion is supported by clinical and experimental data. Indeed, our own preliminary data show that breast cancer cells become dormant upon entering the brain, and that emerging from this state is the rate-limiting step of metastasis. These data indicate that targeting dormant disseminated tumor cells (DTCs) is a logical approach to brain metastasis prevention. However, despite a growing understanding of dormancy mechanisms in common metastatic sites like lung and bone marrow, a parallel understanding of how DTCs are driven into a dormant state in brain has not developed. The overarching goal of this proposal is to address this issue. We will formulate a basic framework for how the brain microenvironment drives DTCs into a dormant state, with support from clinical specimens, so that we can leverage this understanding for therapies that keep DTCs dormant indefinitely. Our recent investigations have revealed that dormant DTCs occupy the brain’s vascular niche, where perivascular astrocytes suppress their outgrowth. We suspect that astrocytic contributions to the parenchymal basement membrane are responsible for DTC suppression, and that these contributions converge on a common receptor: dystroglycan. Therefore, our hypotheses are that: (i) astrocytic basement membrane is a key driver of DTC dormancy, and (ii) dystroglycan function must remain intact for DTCs to interpret these signals. We will test these hypotheses through two specific aims: Aim 1. Determine whether astrocytic basement membrane promotes and sustains DTC dormancy. Aim 2. Elucidate the dystroglycan-mediated signaling axis that effects DTC quiescence in brain. We have brought every relevant resource to bear in order to address these aims. These resources span: (i) long-term intravital imaging to determine the fate of DTCs following ablation of DTC-associated astrocytes; (ii) transgenic mice to measure the outcome of ablating astrocyte derived basement membrane molecules on DTC fate; (iii) rare clinical specimens to establish whether astrocytes and astrocytic basement membrane are asso- ciated with dormant DTCs in humans; and (iv) a host of mutant, over- and under- expression constructs to solve how dystroglycan functions from the outside-in to drive DTC quiescence. The significance and innovation of this work lie in the identification of the first dormancy drivers in brain, ultimately to unravel dystroglycan-driven signaling that effects disseminated breast tumor cell quiescence. This work will set the stage for agonists of dystroglycan function that serve as prophylactics for brain metastasis prevention.