Drugs disguised as human platelets target cancer

Researchers have developed a technique that coats anti-cancer drugs in membranes from the patient's own platelets, to allow drugs to last longer and remain undetected by cancer cells, in order to attack both primary tumours and the circulating tumour cells that cause cancer to spread.

The technique developed for the first time offered two advantages.

First, the surface of cancer cells have an affinity to platelets to which they stick.

"Second, because the platelets come from the patient's own body, the drug carriers are not identified as foreign objects so these last longer in the bloodstream," explained Zhen Gu, assistant professor at North Carolina State University.

''This combination of features means that the drugs can not only attack the main tumour site, but are more likely to find and attach themselves to tumour cells circulating in the bloodstream - essentially attacking new tumors before they start,'' said Quanyin Hu, lead author of the paper and a PhD student in the joint biomedical engineering program.

Blood is taken from a patient, a mouse in this case - and platelets are extracted from that blood.

The isolated platelets are next treated to extract the platelet membranes, that are then placed in a solution containing the anti-cancer drug "Dox".

The solution is then compressed to create nanoscale spheres comprising platelet membranes with the drug.

These spheres are next treated so that their surfaces are coated with another effective anti-cancer drug named "TRAIL".

"When released into a patient's bloodstream, these pseudo-platelets can circulate for up to 30 hours - as compared to approximately six hours for the nanoscale vehicles without the coating," the authors noted.

When a pseudo-platelet comes into contact with a tumour, first, the P-Selectin proteins on the platelet membrane bind to the CD44 proteins on the surface of the cancer cell, and lock it into place.

Next the TRAIL on the pseudo-platelet's surface attacks the membrane of the cancer cell.

Third, the larger cancer cell swallows the nanoscale pseudo-platelet.

The acidic environment inside the cancer cell then starts breaking apart the pseudo-platelet which frees Dox to attack the cancer cell's nucleus.

In the study involving mice, the researchers observed that the use of Dox and TRAIL in the pseudo-platelet drug delivery system proved significantly more effective against large tumours and circulating tumour cells than using Dox and TRAIL in a nano-gel delivery system without the platelet membrane.