Role of Heparan Sulfate and Glycocalyx in Cancer Metastasis
Michelle Zhang1, Solomon Mensah2, and Eno Ebong
1 Department of Chemical Engineering, Northeastern University, Boston, MA
2 Department of Bioengineering, Northeastern University, Boston, MA
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.1 To 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.
Special thanks to Northeastern University, Ming Cheng, Tier 1 for Pilot Grant funding, Professor Vladimir Torchilin, and Mark Niedre
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.
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