Abstract IA06: Mechanism of metastatic migration and invasion in confined matrices
Authors: Reinhart-King Cynthia A. 
Published: March 2017

Abstract
The architecture of the tumor microenvironment is highly heterogeneous, containing areas that vary in the size of matrix fibers, arrangement of fibers, pore size and density[1]. This architecture exerts tight control over cell migration. Importantly, cell migration in 2D is not necessarily governed by the same mechanisms mediating migration in 3D matrices, and as such it is important to study migration in physiologically relevant matrices. As an example, our data and work from others indicates that fiber pore size in 3D matrices alone, independent of collagen density, determine whether cells will migrate through a collagen matrix[2]. In 3D matrices, cells actively probe their environment before committing to a migration direction, and inhibition of this probing can inhibit migration and metastasis[3]. These data suggest that the architecture of the extracellular matrix alone can mediate metastatic migration and is a key element to understanding the molecular mediators of metastatic migration.
In 3D matrices, cells have the ability to remodel this matrix both through enzymatic degradation and fiber reorganization[4]. This remodeling can result in the creation of micron-sized tunnels within the stroma through which cells can travel[5]. While significant work has been performed to investigate the mechanisms by which cells move through homogeneous collagen matrices, less is known about the mechanisms governing cell movements in these tunnels. Just as 2D movements do not always predict 3D movements, molecular regulation of migration in 3D is likely not identical to migration in tunnels. Most notably, when traveling in tunnels, cells do not necessarily need to degrade and manipulate the matrix to migrate. As such, there is a need to treat cell migration in 3D tunnels as distinct from what is known about 2D and 3D migration.
To further investigate cell movements in tunnels within the stroma, we created a microfabricated platform that recapitulates the size and architecture of the tunnels found in vivo. The platform uses micromolding techniques to create micro-sized channels in collagen that can then be seeded with cells and imaged. Cells can adhere to all four walls of the channels as they migrate. In these channels, cells exhibit a similar morphology and cytoskeletal structure to that which is found in vivo. Similar to many microfabricated platforms, this channel system can produce hundreds of identical channels in which cell movements can be observed and investigated.
Using these channels, we have identified several key proteins which regulate cells movements in tunnels. Interestingly, many of these focal adhesion associated proteins play a different role in channel migration than they do in migration in 3D isotropic collagen matrices or 2D planar substrates. In these channels, cells tend to move unidirectionally, and this motion is mediated in part by vinculin[6]. Following vinculin knock down, cells tend to oscillate rapidly in the channels. Migration speed is unchanged but there is a dramatic decrease in cell persistence. Tracking of the Golgi indicate that cell polarity is disrupted. The effect of vinculin on cell migration persistence is mediated in part by FAK, as knockdown of FAK reduces FAK activation, and pharmacological inhibition of FAK phosphorylation disrupts migration in channels.
Cell movements in interstitial spaces and cell-created microtracks are distinct from movements on 2D planar substrates and movements in 3D isotropic matrices. Microfabrication techniques permit the recreation of these tracks in vitro to better understand the molecular mechanisms governing cell movements. Our data indicate that there are numerous critical differences in the molecular regulation of channel migration, suggesting alternate potential therapeutic targets.
1. Carey, S.P., T.M. D'Alfonso, S.J. Shin, and C.A. Reinhart-King, Mechanobiology of tumor invasion: engineering meets oncology. Crit Rev Oncol Hematol , 2012. 83(2): p. 170-83.
2. Carey, S.P., C.M. Kraning-Rush, R.M. Williams, and C.A. Reinhart-King, Biophysical control of invasive tumor cell behavior by extracellular matrix microarchitecture. Biomaterials, 2012. 33(16): p. 4157-65.
3. Huang, F.K., S. Han, B. Xing, J. Huang, B. Liu, F. Bordeleau, C.A. Reinhart-King, J.J. Zhang, and X.Y. Huang, Targeted inhibition of fascin function blocks tumour invasion and metastatic colonization. Nat Commun, 2015. 6: p. 7465.
4. Kraning-Rush, C.M., S.P. Carey, M.C. Lampi, and C.A. Reinhart-King, Microfabricated collagen tracks facilitate single cell metastatic invasion in 3D. Integr Biol (Camb), 2013. 5(3): p. 606-16.
5. Carey, S.P., A. Rahman, C.M. Kraning-Rush, B. Romero, S. Somasegar, O.M. Torre, R.M. Williams, and C.A. Reinhart-King, Comparative mechanisms of cancer cell migration through 3D matrix and physiological microtracks. Am J Physiol Cell Physiol, 2015. 308(6): p. C436-47.
6. Rahman, A., S.P. Carey, C.M. Kraning-Rush, Z.E. Goldblatt, F. Bordeleau, M.C. Lampi, D.Y. Lin, A.J. Garcia, and C.A. Reinhart-King, Vinculin Regulates Directionality and Cell Polarity in 2D, 3D Matrix and 3D Microtrack Migration. Mol Biol Cell, 2016.
Citation Format: Cynthia A. Reinhart-King. Mechanism of metastatic migration and invasion in confined matrices. [abstract]. In: Proceedings of the AACR Special Conference on Engineering and Physical Sciences in Oncology; 2016 Jun 25-28; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2017;77(2 Suppl):Abstract nr IA06.