Platelets direct immunotherapy to cancer cells in mice

Platelets - which help the blood to clot at wound sites - can be used to deliver anti-cancer treatment to the site of a surgically removed tumour, reports a paper published online this week in Nature Biomedical Engineering. The pre-clinical study in mice demonstrates the ability to harness the body’s natural response to a wound to eradicate any remaining cancer cells, halt regrowth of the tumour, and prevent the cancer cells from spreading.

In many cases of diagnosed cancer, surgical removal of the primary lesion is the preferred treatment option. However, any cancer cells left in the surrounding tissue after the tumour is removed may cause the cancer to regrow months later, often as metastasis in another organ. Platelets naturally accumulate at wound sites and interact with tumour cells circulating in the bloodstream. Although immunotherapy - which uses antibodies to activate the immune system to target cancer cells - can be used to help kill individual cancer cells, it is difficult to deliver such antibodies within reach of mobile cancer cells in an efficient manner.

Zhen Gu and colleagues removed platelets from mice, attached an immunotherapeutic antibody - programmed cell death ligand 1 antibody (anti-PDL1) - to the platelets in the laboratory, and then re-introduced them into the mice. They show that, following removal of a primary cancer, platelets with the anti-PDL1 attached to their surface migrate to the surgical site and release the antibodies. They show that this enhances the mice’s immune response to cancer and helps eliminate the cancer’s recurrence. Finally, the authors also show that the platelets recognise cancer cells circulating in the blood before they can develop into a metastatic lesion. However, they note that further research is required before this approach can be trialled in humans, translated into the clinic, or applied to other types of immunotherapy.

doi: 10.1038/s41551-016-0011

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