(12d) Uncovering Mechanisms That Result in Diverse Contact Guidance Behavior Amongst Cancer Cells

Cancer cell invasion is driven
by migration. Often this migration is directed by aligned collagen fibers, a
process called contact guidance. Because of the strong link between directed
migration and aligned collagen fiber orientation, extracellular matrix
alignment has been suggested as a measurable to determine invasion potential. We
have recently shown that different breast cancer cells respond to contact
guidance cues differently. MDA-MB-231 cells, which migrate with a mesenchymal
mode, sense contact guidance cues with high fidelity, but MTLn3 cells, which
migrate with an amoeboid mode, do not sense contact guidance cues. Several
studies have shown that modulating contractility and adhesion through
Rho-family GTPases and integrin activation allows
cells to switch between migrational modes. We were
interested if this plasticity in migrational mode
affects contact guidance.

In this study,
we have used several different approaches for generating contact guidance cues
including microcontact printing, soft lithography and
epitaxial collagen growth to generate lines, ridges and aligned fibrils of
collagen. In addition, we have used pharmacological inhibitors and genetic
approaches to examine the role of Rac and Rho GTPases as well as the activation of b1 integrins in modulating contact guidance
through focal adhesions and the cytoskeleton. Decreasing
contractility by inhibiting Rho-kinase (Y-27632) or partially blocking b1 integrin activation (P5D2 antibody) in
MDA-MB-231 cells diminished contact guidance fidelity on epitaxially
growth collagen fibrils. One the other hand, increasing contractility (calyculin A (CA)) or activating integrins
(MnCl₂) increased contact guidance fidelity in MTLn3 on epitaxially growth collagen fibrils. Interestingly, speed
was not altered. These changes in motility were explained by changes in F-actin
stress fiber density and orientation, myosin light chain phosphorylation and
focal adhesion dynamics and maturation. This suggests that the assessment of
the cell's ability to generate and transmit force in combination with the organization
of the extracellular matrix are important in determining whether contact
guidance occurs leading to cancer cell invasion.

Figure1: Contact guidance
efficiency is altered through contractility and adhesion. Cells
were imaged over time using phase contrast microscopy in the presence of
contractility inhibitors (Y-27632), contractility enhancers (calyculin A (CA)) and integrin activators (MnCl₂).