Oxford-led study uncovers previously unknown function of platelets as DNA 'vacuum cleaners' in the blood, with profound implications for cancer diagnosis and prenatal screening.
Researchers at the University of Oxford have discovered an unexpected and powerful new function for platelets - the tiny blood cells primarily known for their role in blood clotting. The Cancer Research UK-funded study, published in Science , demonstrates that platelets also act as scavengers, capturing and storing fragments of DNA that are circulating in the blood, including fetal DNA and mutated DNA from cancer cells. Analysis of platelet DNA via a simple blood test was found to reveal the presence of even "pre-cancerous" changes - indicating this may be a powerful technique for the early detection and prevention of cancer.
It is already known that fragments of DNA are released into the bloodstream by dead and dying cells. Too much of this "cell-free" DNA is harmful, causing unwanted activation of immune cells or other health complications. Exactly how the body protects against this is not known. The current study suggests that platelets internalise these DNA fragments, thereby playing an important role in clearing DNA fragments from the blood.
Remarkably, the team, led by researchers at the MRC Weatherall Institute of Molecular Medicine , found evidence of fetal DNA within the platelets of pregnant mothers, and mutated DNA in platelets from patients diagnosed with cancer and even those with pre-cancerous conditions. These findings offer new possibilities to refine and improve genetic testing methods used today. Analysis of DNA fragments in the blood is emerging as an important screening method in a number of healthcare settings. However, current approaches discard the platelets and only focus on platelet-depleted blood plasma.
The postdoctoral researcher who led the project, Lauren Murphy , said: 'Our study suggests that platelets might be even more important for our health than we previously realised. It also indicates that current liquid biopsy screening methods are overlooking valuable genetic information that is contained within platelets. Our finding that platelets contain cell-free DNA means the sensitivity of cancer screening tests can be improved, enabling cancers to be detected much earlier than has previously been possible.'
The research team is optimistic that future applications could lead to earlier detection of cancers and other genetic disorders, improving patient outcomes.
Bethan Psaila, Professor of Haematology at the University of Oxford and senior author for the study, said: 'Our discovery that platelets act as tiny DNA dust-busters in the blood was unexpected. One lucky consequence of this is that platelets bear hallmarks of DNA damage that has occurred in all tissues in our body - and analysis of platelets can potentially improve screening tests, including for cancer. This study was a team effort with the Universities of Edinburgh and Swansea and we are hugely grateful to our many collaborators, to Cancer Research UK who funded the study, and in particular to all patients who donate samples for scientific research.'
Dr David Crosby, Head of Prevention and Early Detection Research at Cancer Research UK, which funded the study, said: 'Platelets do not have any DNA of their own and it's interesting and potentially important that they can internalise cancer DNA circulating in the bloodstream. This discovery means that many more parts of a blood sample could be used to find cancers earlier, long before any symptoms appear. It may find clues of cancer that have previously been overlooked.
'Blood tests that can find tiny fragments of DNA shed from tumours are already in development. These 'liquid biopsies' have huge potential in the clinic, both for early detection and to detect cancers that are coming back after treatment. This discovery could dramatically expand that research into new blood tests which use DNA gathered by platelets.
'Further research will be needed to assess which parts of platelet DNA provide the most useful information about cancer and how blood tests can look for them accurately. But this discovery moves us a step closer to finding better ways to catch cancer earlier, when treatment is more likely to be successful.'
The paper ' Platelets sequester extracellular DNA, capturing tumor-derived and free fetal DNA ', is published in Science .
