Disguising drugs as platelets could make them more effective against cancer

30 Sep

Researchers have a developed a new technique that they hope will make anticancer drugs remain in the body for longer and target a range of different cancer cells: coating the drugs in the membranes of platelets, the cells in the blood that bind together to prevent bleeding.

Platelets in the blood.
The surfaces of cancer cells have an affinity for platelets, causing the two cells to stick together frequently.

The technique is detailed in a study published in Advanced Materials, in which it was tested successfully in mice.

Corresponding author Zhen Gu, an assistant professor in the joint biomedical engineering program at North Carolina State University and the University of North Carolina at Chapel Hill, states that there are two key advantages to using platelet membranes to coat anticancer drugs.

“First, the surface of cancer cells has an affinity for platelets – they stick to each other,” he explains. “Second, because the platelets come from the patient’s own body, the drug carriers aren’t identified as foreign objects, so last longer in the bloodstream.”

Not only does this new technique allow drugs to target a cancer’s main tumor site, but the platelet membrane coating increases the chances of the drugs attaching to circulating tumor cells – cells in the bloodstream that cause a cancer to spread to other parts of the body.

In the study, the researchers took blood from mice and collected platelets from the samples. From these platelets, the researchers then extracted the membranes and added them to a solution with a gel containing an anticancer drug called doxorubicin (Dox).

By compressing the solution, the team produced nanoscale spheres comprised of a platelet membrane outer shell with a Dox-gel core. They then coated the surfaces of these spheres with another anticancer drug called TRAIL that is known to be effective at attacking cancer cell membranes.

Disguised cancer drugs circulated for up to 30 hours in bloodstream

When the platelet membrane-coated spheres encounter cancer cells, specific proteins on the platelet membrane (P-Selectin) bind to proteins on the surface of the cancer cell (CD44). This binding then locks the sphere in place.

The coating of TRAIL on the surface of the sphere then proceeds to attack the cell membrane of the cancer cell. The sphere then enters the larger cancer cell, at which point the acidic environment begins to break down the platelet membrane coating.

As the platelet membrane is broken down within the cancer cell, the Dox-gel within is freed and attacks the nucleus of the cancer cell.

Disguising the anticancer drugs as platelets enabled the drugs to circulate in the mice’s bloodstreams for up to 30 hours – a significant improvement on the 6 hours observed for nanoscale drugs delivered without the platelet membrane coating.

In addition to lasting longer, the nanoscale drugs delivered with the platelet membranes were significantly more effective at targeting large tumors and circulating tumor cells than the nanoscale drugs delivered without the platelet membrane.

Prof. Gu explains how the team hopes to take this research further:

“We’d like to do additional preclinical testing on this technique. And we think it could be used to deliver other drugs, such as those targeting cardiovascular disease, in which the platelet membrane could help us target relevant sites in the body.”

This is not only recent study to examine the potential role of platelets in cancer treatment. Previously, Medical News Today reported on a study that found the common antiplatelet medication aspirin may double the survival chances of patients with gastrointestinal cancers.

The researchers believe this could be because circulating tumor cells may use platelets to protect themselves from the immune system. By blocking the functioning of the platelets, aspirin may leave circulating tumor cells vulnerable to attack.

Written by James McIntosh

Copyright: Medical News Today

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