Mechanism and Control of the "Predatory," Levy Walks of Metastatic Cancer Cells

描述(申请人提供)：转移细胞在人体内的迁移可以在不同的位置种植继发性癌症，通常会给患者带来致命的后果。数十年的密集研究表明，转移性癌细胞与非转移性癌细胞在遗传学、分子组成和运动性增强方面存在差异。尽管有这些进展，但目前还没有批准的药物可用于靶向转移性癌细胞的运动。这在很大程度上是由于我们对 这些过程是转移细胞运动性增强的基础。我们最近发现，非转移细胞和转移细胞的迁移方式是完全不同的。当非转移细胞执行简单的扩散随机行走时，它们在所有实验系统中的转移变体(1D微轨迹、3D胶原凝胶和在小鼠皮肤中的体内)以超扩散的方式移动，并执行所谓的L行走，其中的步长时间是根据具有重幂定律尾部的概率分布绘制的。L步道结构的特点是一簇簇的小台阶，中间偶尔有很长时间的“飞跃”。重要的是，从随机过程理论中知道，L行走代表了一种最优搜索策略--这是寻找稀有猎物的动物捕食者经常采用的一种策略。在这种背景下，转移细胞可以被视为“细胞捕食者”，以一种最大化的方式在人体内导航，以最大限度地找到合适的位置来播种转移。如我们所示，通过协同抑制Rho和Rac通路，这些L步态可以恢复为“良性”的、纯弥漫性的步态--这一发现为合理控制和最终限制 转移细胞在人体内执行捕食性行走。我们目前的建议建立在这些早期发现的基础上，并将实验与理论相结合，以定量了解L所走的转移性癌细胞背后的细胞和分子机制。具体地说，微纳米制造和表面功能化方案将被结合起来，以开发一个微流体平台，利用该平台在不同条件下进行细胞运动的平行筛选。我们将使用大量有统计学意义的细胞在线性一维微轨迹上移动的动态成像来研究L行走的机制。包括化学抑制剂和RNAi在内的分子生物学方法将被用来扰乱基于肌动蛋白的运动机械的各个部分及其对L行为的贡献。基于最大似然估计和Akaike权重的严格统计方法将用于区分L的步态和其他运动策略。这些机制研究将产生一个独特的条件数据集，在这些条件下，L行走的表型可以恢复为弥漫性表型。此外，还将构建一个预测性的理论模型，将Rho/Rac通路的状态与L的步行运动表型联系起来。我们预计，对转移细胞L行走机制的了解和控制将为转移癌的治疗提供新的策略。

DESCRIPTION (provided by applicant): Migrations of metastatic cells throughout the human body can seed secondary cancers at various locations, often with deadly consequences to the patient. Decades of intense research have established that metastatic cancer cells differ from the non-metastatic ones in terms of their genetics, molecular composition, and their increased motility. Despite these advances, there are currently no approved drugs available that target motility of metastatic cancer cells. This is in large part due to our limited understanding of what processes underlie the increased motility of the metastatic cells. We have recently shown that non-metastatic and metastatic cells migrate in fundamentally different ways. While non-metastatic cells execute simple, diffusive random walks, their metastatic variants in all experimental systems (1D microtracks, 3D collagen gels and in vivo in mouse skin) move superdiffusively and perform so-called L¿vy walks in which step-times are drawn from probability distributions with heavy power-law tails. L¿vy walk path structure is characterized by clusters of small steps separated by occasional but long "flights". Importantly, it is known from the theory of stochastic processes that L¿vy walks represent an optimal search strategy - one that is often employed by animal predators looking for scarce prey. In this context, metastatic cells can be viewed as "cellular predators" navigating human body in a manner that maximizes their chances of finding suitable loci for seeding metastases. As we have shown, these L¿vy walks can be reverted to the "benign", purely diffusive walks by synergistic inhibition of Rho and Rac pathways - this finding paves the way to rationally control and ultimately limit the ability of metastatic cells to execute their predatory walks throughout the human body. Our current proposal builds on these early findings and combines experiments with theory to gain quantitative understanding of the cellular and molecular mechanisms that underlie L¿vy walks of metastatic cancer cells. Specifically, micro- and nanofabrication and surface functionalization schemes will be combined to develop a microfluidic platform with which to perform parallel screens of cell motility under different conditions. Dynamic imaging of large, statistically significant numbers of cells moving on linear 1-D microtracks will be used to investigate the mechanism of L¿vy walks. Molecular biology approaches including chemical inhibitors and RNA interference will be employed to perturb various parts of the actin-based motility machinery and their contribution to L¿vy behavior. Rigorous statistical methodologies based on maximum likelihood estimates and Akaike weights will be used to discriminate L¿vy walks from alternative motility strategies. These mechanistic studies will yield a unique dataset of conditions under which the L¿vy walking phenotype can be reverted to a diffusive one. Furthermore, a predictive theoretical model will be constructed relating the status of the Rho/Rac pathways to the L¿vy walking motility phenotype. We envision that the understanding and control of the L¿vy walks mechanism of metastatic cells will lead to new strategies for treating metastatic cancer.