Role of Heparan Sulfate and Glycocalyx in Cancer Metastasis

Role of Heparan Sulfate and Glycocalyx in
Cancer Metastasis

Michelle Zhang¹, Solomon Mensah², and Eno
Ebong

¹Department of Chemical
Engineering, Northeastern University, Boston, MA

² Department of Bioengineering,
Northeastern University, Boston, MA

Abstract

The endothelial glycocalyx is a network of proteoglycans and
glycoproteins located in the vascular endothelium of blood vessels.¹
Composed of complex polysaccharides, the glycocalyx layer lines the lumen and
acts as a modulator for cell to cell recognition and adhesion between
neighboring cells.¹ Much research has been conducted to investigate
the role of the glycocalyx in diseases such as atherosclerosis in relation to
white blood cell adhesion and cancer with
metastatic tumor cell adhesion. The interest of this abstract is to investigate
the role of the glycocalyx in the attachment of cancer cells to the endothelial
cell line blood vessel wall.

The glycocalyx is primarily composed of the glycosaminoglycan
(GAG) side chains: heparan sulfate, hyaluronic acid, and chondroitin.²
Heparan sulphate makes up 50-90% of the glycocalyx and is responsible for
cellular response to environmental stimuli.³ As cancer cells
circulate through the blood stream they bind and activate neighboring
endothelial cells to begin the formation of secondary tumors. Cancer cells in
the bloodstream adhere to the endothelium through a process of tethering and
rolling where tumor ligands attach to adhesion molecules in the glycocalyx
layer.² The distance between the adhesion molecules on the
endothelial surface and the corresponding ligands on tumor cells is dependent
upon the thickness of glycocalyx, which serves as a barrier to
tumor-endothelium adhesion.² We hypothesize that shedding and degradation
of the glycocalyx can lead to better access for tumor cells.

The glycocalyx layer can be degraded with the introduction of the
enzyme Heparinase III that cleaves the heparan sulfate from the core glycocalyx
layer. With the removal of heparan sulfate, the glycocalyx layer collapses due
to loss of alignment.¹To test the
hypothesis, we are comparing healthy RFPEC (rat fat pad endothelial cells)
against cells that have been treated with Heparinase. Heparan sulfate is
targeted due to its abundance in the glycocalyx layer. Experimentation
involves comparing RFPEC that have been treated with Heparinase III against a
control. Both healthy control cells and Heparinase treated endothelial cells
are exposed to cancer cells and washed out. The remaining cancer cells that are attached to the endothelial
cells are visualized with a confocal microscope for cell counting. Images
obtained under immunostaining will indicate areas of cancer cell adhesion.
Initial experimentation reveals that in the control, for every 10,000 endothelial cells, an average of 11.9 cancer cells
attached. For every 10,000 Heparinase treated endothelial cells, an average of 17
cancer cells attached, resulting in a 43% increase in tumor adhesion in the Heparinase
III treated cells as compared to the control. This result supports the
prediction of increased attachment due to enzyme degradation.

Cancer metastasis is responsible for approximately 90% of all
cancer-related deaths.² As the adhesion to endothelial cells is a
part of this process, it is critical to understand the role of the glycocalyx
in cancer cell attachment. Knowledge in this area can lead to the development
of treatments to restore the glycocalyx as a more effective barrier against
tumor adhesion.

Acknowledgements

Special thanks to Northeastern University, Ming Cheng, Tier 1 for
Pilot Grant funding, Professor Vladimir Torchilin, and Mark Niedre

References

1.      
Giantsos-Adams KM, Koo AJ-A, Song
S, et al. Heparan Sulfate Regrowth Profiles Under Laminar Shear Flow Following
Enzymatic Degradation. Cellular and Molecular Bioengineering. 2013;6(2):160-174.

2.      
Mitchell MJ, King MR. Physical Biology in Cancer. 3. The role of
cell glycocalyx in vascular transport of circulating tumor cells. American
Journal of Physiology - Cell Physiology. 2014;306(2):C89-C97.

3.      
Reitsma S, Slaaf
DW, Vink H, van Zandvoort
MAMJ, oude Egbrink MGA. The
endothelial glycocalyx: composition, functions, and visualization. Pflugers Archiv . 2007;454(3):345-359.