Novel Function for Platelets: Nucleus-Free Cell Fragments Can Reduce Metastasis by Helping Preserve Vascular Barrier, Making Blood-Vessel Wall Selectively Impermeable, Thereby Reducing Spread of Tumor Cells to Other Parts of Body

Scientists at Uppsala University in Sweden have discovered a hitherto unknown function of blood platelets in cancer. In mouse models, these platelets have proved to help preserve the vascular barrier which makes blood-vessel walls selectively impermeable, thereby reducing the spread of tumor cells to other parts of the body. The study results were published online on June 25, 2020 in Cancer Research. The article is titled “Platelet-Specific PDGFB Ablation Impairs Tumor Vessel Integrity and Promotes Metastasis.” Platelets (, also known as thrombocytes, are tiny cell fragments, without a nucleus, that form in the bone marrow and circulate in the blood. If we are injured and start bleeding, platelets clump together, sealing off the wound while also helping the blood to coagulate. When the platelets are activated--which occurs not only in wounds, but also in tumors--the substances known as growth factors contained in the platelets are released into their immediate surroundings. One of these growth factors is platelet-derived growth factor B (PDGFB). In the Uppsala study, the researchers investigated what happens when the PDGFB in platelets, but not in other cell types, is deleted in individuals with cancer. PDGFB from platelets was found to be essential, to attract supporting cells to the tumor blood vessels. In healthy tissue, on the other hand, the platelets did not to perform this function. If PDGFB was lacking in platelets, the quantity of circulating tumor cells increased and they spread to other parts of the body to a much higher degree. Previous studies have shown that PDGFB from cells of another kind, endothelial cells that line the inside of blood vessels, is necessary to attract supporting cells to the vessels when they form.
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