(71b) Extracellular Matrix Stiffness and Drug Resistance in Carcinoma

Extracellular
Matrix Stiffness and Drug Resistance in Carcinoma

Thuy
V. Nguyen and Shelly R. Peyton

University
of Massachusetts, Amherst, MA, USA

The in
vivo tumor niche is comprised of both cells and extracellular matrix (ECM),
which provides important physical and chemical cues, that regulate tumor cell
growth, motility, and perhaps, the ability of cells to respond to drugs. We
hypothesize that receptor tyrosine kinase (RTK) inhibitors, in particular, may
show misleading efficacy when tested on cells cultured on tissue culture
plastic, due to the unnatural microenvironment. In response, we are developing
a novel high-throughput biomaterial system to study how carcinoma cells respond
to RTK inhibitors in the presence of a physiologically relevant matrix cues.

During disease progression in tumor
microenvironment, the ECM is remodeled by fibroblasts. Collagen IV and laminin are replaced by fibrillar
collagen I, III, and fibronectin. This ECM turnover increases the total protein
content as well as the local tissue modulus (from less than 1kPa to 20-100kPa
or more). In order to capture these physical and chemical tissue changes, we
are developing a novel, high-throughput, PEG-PC hydrogel biomaterial system. Briefly,
poly(ethylene glycol) dimethacrylate
(PEG) and the zwitterion 2-Methacryloyloxyethyl phosphorylcholine (PC) form an
optically clear hydrogel via radical polymerization in a silane-treated
glass 96-well plate. We can control the modulus
of the hydrogels anywhere from one to hundreds of kPa
by tuning the PEG crosslinker content. The PC zwitterion is extremely
hydrophilic, which allows our PEG-PC gels to achieve lower moduli (we can form
gels with only 0.5 wt% PEG crosslinker), and block
non-specific protein interactions better than PEG-only gels. We incorporate
small amounts of acrylate-PEG-succinimidyl
valerate, which is an amine-reactive group, to couple
full-length ECM proteins to the gel surface. We are developing this tunable
hydrogel system to study how tissue modulus and integrin-binding ligands
control the ability of carcinoma cells to respond to RTK inhibitors.  As a mimic of precancerous tissue, we have a
5kPa gel with collagen IV, fibronectin, and laminin, and as a cancerous tissue, we have 20 and 55kPa
gels with collagen I, III, and fibronectin. We have used this system to test
carcinoma cell (liver: HEP3B, and breast: MDA-MB-231, MCF7, SKBR-3, and BT549)
response to sorafenib, an FDA-approved RTK inhibitor. We are quantifying the
cell response (apoptosis) with a proliferation assay and a real-time caspase
3/7 reporter.

Thus far, we have observed
that both breast and liver carcinoma cells exhibit chemo-resistance in cancerous
microenvironments. In fact, at least 30% additional sorafenib is required to
inhibit proliferation in cells on cancerous tissues relative to healthy tissues.
This resistance is coincided by visible morphological changes as well, wherein
the cancerous microenvironment promotes less cell-cell contact and a spindle
shape. We are currently investigating combinatorial treatments by targeting
ERK/Akt signaling pathways to overcome matrix-conferred resistance. The drug
resistance we have observed here may be one reason that drugs that show
efficacy on tissue culture plates eventually fail in clinical trials.  We propose that this high-throughput
biomaterial system may serve as a system that pharmaceutical companies can use
to rule out false positives and potentially save billions
of dollars in the drug development pipeline.

Presenting Author

Thuy V. Nguyen

Graduate student

Department of Chemical Engineering
University of Massachusetts

686 North Pleasant Street

159 Goessmann Lab

Amherst, MA 01003

Phone number: 404-933-4077

Email: tnguyen@ecs.umass.edu