Platelets against metastases
Platelets have been found to have a new function
Denis Gordeev, Naked Science
Platelets are small nuclear–free blood cells. Their main functions are the formation of primary plugs that close the sites of vascular damage, and the acceleration of plasma coagulation reactions. Recently, it has also been found that these shaped elements of blood play an important role in tissue regeneration, isolating various growth factors and thereby stimulating cell growth and division.
Scientists from Uppsala University in Sweden have discovered another function of platelets, manifested in the development of oncological processes. During experiments on model mice, researchers have shown that these blood elements are able to make the walls of blood vessels selectively impenetrable, thereby reducing the rate of spread of degenerated cells throughout the body.
One of the substances that platelets secrete is PDGFB protein, platelet growth factor B. In cancerous tumors, this biochemical mediator helps attract so-called supporting cells into the blood vessels. At the same time, platelets do not perform such a function in healthy non-degenerate tissue.
Platelets (red) collect on the vessels that feed the tumor (green). Drawings from an article in Cancer Research.
Experiments on model animals have shown that with a lack of PDGFB, the number of tumor cells circulating in the blood, as well as the rate of their spread throughout the body, increased markedly. An article about this was published in the journal Cancer Research (Zhang et al., Platelet-specific PDGFB ablation impairs tumor vessel integrity and promotes metastasis).
In addition, scientists have noticed another interesting pattern associated with platelet growth factor in tumors. As you know, these neoplasms require an extensive network of small vessels. To build them in healthy tissue, a growth factor from other endothelial cells is needed. But when creating a mesh of vessels in a tumor, PDGFB is also needed. Thus, platelets contribute to the additional strengthening of the walls of these vessels, preventing cancer cells from passing through them.
Platelet behavior in healthy vessels (left) and in vessels feeding the tumor (right).
Many previous studies show that platelets can contribute to the spread of cancer in the body. In addition, from a medical point of view, reducing the activity of these cells can be useful to prevent the appearance of blood clots. However, the work of Swedish scientists demonstrates that platelet activation in cancer can be useful to the body.
"PDGFB, released when platelets are activated, can help strengthen the vascular barrier in tumors, thereby countering the spread of cancer cells," says Anna–Karin Olsson, one of the authors of the study. "This makes it necessary to take into account the specific functions of the molecules [released from] platelets when we develop new ways to treat cancer."
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