Tumor Mechanobiology
Focus on the role of the biophysical
properties of the ECM in tumor progression
A review from the literature
Definition and scales
Matrix stiffness modulates proliferation, chemotherapeutic
response, and dormancy in hepatocellular carcinoma cells.
Schrader J. et al., Hepatology. 2011
Cellular
Mechanobiology
Molecular/Cellular
Mechanotransduction
Tissue
Mechanobiology
Cell stiffness,
Cell contractility,
Cell rheology
Matrix stiffness,
deformability
ROCK-Driven Actomyosin Contractility
Induces Tissue Stiffness and Tumor Growth.
Kümper S and Marshall CJ, Cancer Cell. 2011
Pathak A. et al., PLoS One, 2011
Discher DE. et al. Science, 2005
Tissue rigidity influences cell behavior
Engler JA. et al., Cell, 2006
Discher DE. et al, Science 2005
Changes in the physical/mechanical
environment during tumor growth
• Forces generated by the expanding tumor in a restrictive
tissue space
• Denser/Stiffer tissue that forms around a tumor
• Increased interstitial pressure and altered fluid flow
patterns caused by the growth of new blood vessels
Paszek MJ, et al. J Mammary Gland Biol. and Neoplasia, 2004
Shieh AC. Annals of Biomedical Eng. 2011
Outline
I. Can we use tumor biophysical properties as
prognostic or diagnostic tools?
II. How do tumor cells respond to physical/
mechanical changes of the environment?
III. Matrix stiffening: cause or consequence?
Outline
I. Can we use tumor biophysical properties as
prognostic or diagnostic tools?
II. How do tumor cells respond to physical/
mechanical changes of the environment?
III. Matrix stiffening: cause or consequence?
Tumor mechanobiology
“The denser the breast/ the liver,
the worst the prognosis”
“The stiffer the matrix,
the more aggressive the tumor”
“The denser the breast/the liver,
the worst ”
Women who have a breast density of 75 percent or
higher on a mammogram have a risk of breast cancer
that is four to five times greater than that of women
with little or no density, making mammographic
breast density one of the strongest biomarkers of
breast cancer risk.
“The stiffer the matrix,
the more aggressive the tumor”
Elastography: a non-invasive method to
measure tissue stiffness
• Ultrasound or MR-based techniques for measuring stiffness
by the difference in the velocity of the elastic shear wave
propagation across a given tissue
• The force is generated by applying pressure.
www.breastcancer.about.com
An increased stiffness is diagnostic of
diseased tissue
Fibrotic Liver
Elastogram
(or strain map)
Conventional
MRI
Normal Liver
Venkatesh SK, et al. A J Roentgenology. 2008
Increased tissue stiffness can assist intervention and
therapeutic decisions: biopsy, treatment
Assessing prognosis and candidacy for treatment in patients with
chronic liver disease.
 Spare patients that don’t need it the discomfort and risk of
complications associated with liver biopsy
Yin et al,. Clin Gastroenterol Hepatol. 2007
An increased stiffness is prognostic of
disease outcome
An increased stiffness is diagnostic of breast
tumor lesions
Invasive Lobular Carcinoma
X-Ray
Mammography
Ultrasound
Elastography
Breast Fibroadenoma
 When a mechanical compression or vibration is applied, the tumor deforms less than the
surrounding tissue i.e. the strain in the tumor is less than the surrounding tissue.
Collagen density promotes mammary tumor
initiation and progression
“ Abstract
Background: Mammographically dense breast tissue is one of the greatest
risk factors for developing breast carcinoma. Despite the strong clinical
correlation, breast density has not been causally linked to tumorigenesis,
largely because no animal model has existed for studying breast tissue
density. Importantly, regions of high breast density are associated with
increased stromal collagen.
“
• Model system:
Col1a1tmJae mouse crossed with MMTV-PyMT mouse
 double-transgenic tumor model with increased stromal
collagen in mouse mammary tissue.
Provenzano P .et al., BMC Medicine, 2008.
Increased stromal collagen in mouse mammary
tissue significantly increases tumor formation
10 week-old mice; Collagen staining: Picrosirius red
Provenzano P et al., BMC Medicine, 2008
Increased stromal collagen in mouse mammary tissue
significantly increases metastasis formation
Provenzano P et al., BMC Medicine, 2008
Definition of tumor-associated collagen
signatures
TACS-3: radially aligned collagen fibers, correlates with local
invasion of tumor cells
Provenzano P et al., BMC Medicine, 2008
Can these “tumor-associated collagen
signatures” be used as a prognostic marker?
The relative concentration of collagen and the orientation of fibers with respect to epithelial
cells was assessed using SHG imaging on 196 biopsies.
Yes!
 Statistical score was developed to determine :
-whether TACS-3 is present in clinical histopathology samples from patients
- whether TACS3 correlated with patient survival
Yes!
Conklin, MW. Et al., AJP, 2011
Outline
I. Can we use tumor biophysical properties as
prognostic or diagnostic tools?
Yes!
II. How do tumor cells respond to physical/
mechanical changes of the environment?
III. Matrix stiffening: cause or consequence?
Outline
I. Can we use tumor biophysical properties as
prognostic or diagnostic tools?
II. How do tumor cells respond to physical/
mechanical changes of the environment?
III. Matrix stiffening: cause or consequence?
The stiffer the matrix, the more
aggressive/invasive the tumor?
Tumor cells but nor normal cells stiffen in
response to stiffer environment
• Technique: Particle-tracking microrheology (PTMR)
• Tracking the Brownian motions of individual tracer beads embedded
within the cells using ballistic particle delivery system
• The particles motion reflect the intracellular viscoelasticity of the cells.
 MCF10A possessing ErbB2 transforming potential stiffen (G’p) in response to
elevated matrix stiffness (G’c), whereas non-transformed MECs don’t
 Increased intracellular stiffening correlated with a more motile phenotype
Baker EL. et al., Biophys. J., 2010
Matrix rigidity modulates tumor cell
proliferation, morphology and migration
• Technique: 96-well plate system that arrays colI-conjugated
PA gels that increase in stiffness by at least 50-fold across the
plate
Tilghman R. et al., PLoS One, 2010
Matrix rigidity modulates tumor cell
proliferation, morphology and migration (2)
A549 cells
Tilghman R. et al., PLoS One, 2010
Stiffness and adhesivness modulate tumor cell
mechanotransduction and migration
• On stiff ECMs, more protrusive
adhesions are stabilized due to
higher Rho and Rac activation
levels, leading to maximal stress
fiber contractility, and rear
adhesions progress through the
initiation-rupture cycle rapidly.
Both of these promote higher
migration speeds
Pathak A. and Kumar S., PLoS One, 2011
Stiffness and adhesivness modulate tumor cell
mechanotransduction and migration (2)
• Lower ligand-density surfaces require higher ECM
elasticities to reach the maximum migration speed,
whereas higher ligand-density surfaces enhance
migration speed on relatively soft ECMs.
Pathak A. and Kumar S., PLoS One, 2011
Matrix rigidity governs the formation of
invadopodia
 On hard PA, invasive MCF10ACA1d produced more invadopodia and
degraded more ECM than on soft PA.
Alexander NR. et al., Current Biol. 2008
Cell, 2009
 Model: MMTV-Neu
Mammary glands conditioned with LOX expressing
fibroblasts were stiffer and promoted tumor growth
1) LOX conditioning of the mammary gland
results in more fibrillar collagen and more
linearized collagen.
2) LOX-conditioned mammary gland
favors tumor progression
 Signaling:
-Integrin Clustering
-Enhancement of PI3K Signaling
Levental KR et al., Cell, 2009
Cancer patients expressing high levels of LOX
have poor outcome
Breast Cancer Patients
(ER neg.)
H&N Cancer Patients
Erler J et al., Nature, 2006
Inhibition of LOX decreased metastasis
formation in vivo
Model: Orthotopic injection of MDA-MB-231
in the mammary fat pad of nude mice.
Erler J et al., Nature, 2006
The stiffer the matrix, the more
aggressive/invasive the tumor?
Yes!
Outline
I. Can we use tumor biophysical properties as
prognostic or diagnostic tools?
II. How do tumor cells respond to physical/
mechanical changes of the environment?
III. Matrix stiffening: cause or consequence?
Can the physical properties of the 3D environment
act as an initiating event of tumorigenesis?
• Question: What is the impact of mechanical stimulation on
the initiation of colon cancer.
• Model System:
• Colon explants
• The deformation of the tissue induced by compression was observed
by two-photon excitation (2PEF) microscopy of the endogenous tissue
fluorescence
Whitehead J. et al., HFSP Journal, 2008
Myc and Twist1 expression is induced by mechanical
stimulation of APC deficient but not WT colon
Whitehead J. et al., HFSP Journal, 2008
b-catenin nuclear translocation is induced by
mechanical stimulation of APC1638N/+ but not WT colon
 When APC is limiting, mechanical strain (intestinal transit or tumor
growth), can be interpreted by cells of preneoplastic colon tissue as a
signal to initiate a b-catenin dependent transcriptional program
characteristic of cancer.
Whitehead J. et al., HFSP Journal, 2008
Remodeling of the ECM is in part induced by
the tumor cells
1.
Cell
mechanotransduction
2. Secretion of ECM remodeling
enzymes: transglutaminases,
lysyl oxidases, etc.
Matrix
remodeling
3. Role of the stromal cells in environment remodeling.
Before, after or in synergy with the tumor cell-induced remodeling