Cell migration is a hallmark of metastasis, a most common cause of death from cancer. Research has established that metastatic cancer cells differ from the non-metastatic ones in terms of their genetics, molecular composition, and 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 f 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 move not only superdiffusively, but also 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". The importance of this finding is that 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 showed, these L?vy walks can be reverted to the purely diffusive walks by synergistic inhibition of Rho and Rac pathways - this finding paves the way to rationally controlling and ultimately limiting the "predatory" walks of metastatic cells. Our current application aims to develop conceptually novel technological platform for quantitative analysis of L?vy walk motility of metastatic cancer cells. Specifically, micro- and nanofabrication and surface functionalization schemes will be combined to develop high-throughput cell migration assay in which linear 1D microtracks will be integrated with 96-well format. Software modules will be developed to automate the microscopy and image acquisition/analysis and will be interfaced with data analyses and processing based on statistical-physical models. A set of 50 genes known or predicted to be involved in cell migration - by regulating filamentous actin (F-actin) polymerization, formation of F-actin contractile bundles or microtubule-F- actin crosstalk - will b targeted in a focused short interfering (si) RNA screen. The ability of siRNAs to affect L?vy walks will be quantified over large populations of cells using the fully automated 1D microtrack assay. These studies will result in the identification of novel regulators and/or regulator combinations whose inhibition abrogates metastatic cell L?vy walks. The material systems developed in the context of this application will constitute a versatile technological platform extendable to large scale RNA interference and chemical library screens for the discovery of new drug targets and anti-motility/ anti-metastasis drugs.

Public Health Relevance

We have recently discovered that as cancer cells metastasize, they develop the so-called L?vy walking navigation strategy typically used by animal predators searching for scarce resources. This skillful mode of cell motility can help the metastatic cells to seed new tumors. The research we propose aims at the development of technology with which to (i) study this predatory mode of cell motility in analytical precision;and (ii) facilitate the discovery of proteins whose inhibition would revert the metastatic L?vy walkers into benign, diffusive cells.

National Institute of Health (NIH)
National Cancer Institute (NCI)
Exploratory/Developmental Grants (R21)
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Special Emphasis Panel (ZCA1-SRLB-Q (O1))
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Knowlton, John R
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Northwestern University at Chicago
Engineering (All Types)
Schools of Engineering
United States
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Wilk, Gary; Iwasa, Masatomo; Fuller, Patrick E et al. (2014) Universal area distributions in the monolayers of confluent mammalian cells. Phys Rev Lett 112:138104