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Wake Forest Physics… |
WFU Biochemistry Colloquium
TITLE:
Breast Cancer Cell Mechanical Properties and
Migration on Collagen I Matrices with Tunable Elasticity
SPEAKER:
Amanda Smelser
TIME: Monday July 25, 2016 at 2:00 PM
PLACE: Room 155 A/B Biotech Place
ABSTRACT
Cell migration requires mechanical interactions
between the intracellular cytoskeleton and the extracellular matrix. The
goals of this work were to compare mechanical properties of metastatic
and non-metastatic cells, and to develop a method for testing the effect
of microenvironment elasticity on cancer cell migration.
The viscoelastic modulus, G*, of cell cytoplasms was determined from
mean-square displacements (MSDs) of peroxisomes. Peroxisome motion is
not purely thermally-driven; ATP-dependent cellular processes contribute
to their random motion, confounding measurements of G*. The Brownian
components of peroxisome MSDs in normal, tumorigenic, and metastatic
cells were determined by treating them with blebbistatin or sodium azide
and 2-deoxy-D-glucose to inhibit ATP-dependent processes. A generalized
Stokes-Einstein equation was used to compute G* from these MSDs.
The values of G* obtained from the Stokes-Einstein equation
agreed with those acquired by active microrheology in similar
cell lines. Moreover, the viscoelastic moduli of metastatic breast cells
(MDA-MB-231) were significantly (p <0.005) lower than those of normal
mammary epithelial cells.
Testing the effect of microenvironment elasticity on cell migration
requires a matrix to which cell integrins can bind, but for which
elasticity can be tuned independently of the density of these binding
sites. Collagen I matrices were tuned to a breast cancer- relevant range
of elasticities (1 to 6 kPa) by first functionalizing lysine groups in
collagen I with glycidyl methacrylate (GMA). Nearby pairs of GMA groups
were then crosslinked by free radicals generated when a photoinitiator,
lithium acylphosphinate, was irradiated by 365 nm photons. MDA-MB-231
cells survived the irradiation by 365 nm light and migrated on these
matrices.
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