DNA Analysis will Build an Internet of Living Things
When cells die in our body, they burst, shedding DNA, which ends up in our blood flow. Cells can die for many reasons: from a natural process of ageing, as a result of disease or organ death. They also die at every stage in life. Even as a foetus grows, the continuous death of its cells means that its DNA is transferred through the placenta into the blood of the mother. A mother’s blood has about ten full foetal genomes per millilitre, which means that a foetus’s DNA can be sequenced while still in the womb.
The same process happens with cancer. Cancer cells, due to their fast growth, die quickly, constantly shedding their DNA into the bloodstream, even at an early stage of the disease. Detecting cancerous DNA would enable much earlier detection.
Recently, Dennis Lo, a chemical pathologist at the Chinese University of Hong Kong who invented the maternal blood-DNA test, performed a cancer biopsy while tracking the tumour’s DNA concentration in the patient’s blood. Performing blood tests every 15 minutes, his team showed that as the tumour was removed, levels of its DNA in the blood dropped.
“If you take a patient’s sample of blood, you can find the tumour DNA,” says Clive Brown, CTO of biotech company Oxford Nanopore. “If part of the tumour is missed, you can still spot its DNA in the blood, so you can know if the surgery has been successful or not.”
Lo couldn’t track the DNA concentration in real-time, but in 2016, we will be able to use portable sequencers such as Oxford Nanopore’s MinION, a USB-stick device that uses nanopore technology to sequence DNA on the spot.
“DNA changes all the time,” Brown says. “If you drink alcohol, your liver cells start to die — they shed DNA and your gene expression changes. If you get infections or a virus, you’ll have that DNA in the blood. If you think of your blood as like a sewer, everything is in it — and it’s dynamic. There’s a lot of stuff in there that’s irrelevant, but you can measure a baseline and then, one day, something changes — some new things appear that aren’t there normally.”
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