Abstract

Invasion of cancer cells into the surrounding tissue is an important step during cancer progression and is driven by cell migration. Cell migration can be random, but often it is directed by various cues such as aligned fibers composed of extracellular matrix (ECM), a process called contact guidance. During contact guidance, aligned fibers bias migration along the long axis of the fibers. Contact guidance cues are known to develop in the tumor microenvironment (TME) and contact guidance has been shown to be an important aspect of cancer progression.

Epitaxially grown, aligned collagen fibrils are unique in their ability to show cell-type differences in contact guidance, likely due to physiologically relevant assembly of collagen fibrils. These cell type differences are also seen in 3D aligned collagen networks assessed in our lab as well as invasion assays in mouse models of cancer. MDA-MB-231 cells perceive the directional signal of highly aligned type I collagen fibrils with high fidelity, elongating to large extents and migrating directionally. Interestingly, behavior in MTLn3 cells differs. While highly aligned type I collagen fibril patterns facilitate spreading and random migration of MTLn3 cells, it does not support elongation or directed migration.

The directionality of highly contractile and adhesive MDA-MB-231 cells can be diminished by inhibiting Rho kinase or β1 integrin binding. Inversely, the directionality of less contractile and adhesive MTLn3 cells can be enhanced by activating contractility or integrins. Subtle, but quantifiable alterations in myosin II regulatory light chain phosphorylation on stress fibers explain the tuning of contact guidance fidelity, separate from migration per se indicating that the contractile and adhesive state of the cell in combination with collagen organization in the TME determine the efficiency of migration.

Amplification or dampening of contact guidance with respect to a particular collagen fibril organization is seen under different conditions, suggesting that not only does contractility and proteolytic activity alter the ability of cells to remodel the ECM, but also their ability to respond to it.

MDA-MB-231 cells exerted higher speed on intermediate stiff transferred PDMS and soft 2000Pa polyacrylamide, but exert lower speed on extremely soft 200Pa polyacrylamide. MTLn3 cells exerted higher speed on intermediate stiff substrates but lower speed on very soft substrate. Cell directionality of MDA-MB-231 cells on all substrates does not have significant difference. This also happens for MTLn3 cells. It appears that the stiffness of substrate does not play a large role in contact guidance.