Microscopic DNA robots could choke off tumours
If humans turn out to be anything like micropigs then scientists may have developed a potent new weapon in the war on cancer.
The blood supply that tumours rely on for oxygen and energy can be choked off by fleets of "nanorobots" made out of DNA, early experiments show. The machines, which are so small that about 20 million would fit on to a pinhead, have shrunk human lung, breast and ovarian cancers in mice.
They also appeared to have no harmful side-effects when they were injected into Bama miniature pigs, which are roughly the size of an Airedale terrier but have a human-like physiology.
While there is much to be done before the treatment can be tested on humans, the study suggests that the long-cherished dream of healing the body with tiny autonomous contraptions could be nearing fruition.
"I think we are much closer to real, practical applications of the technology," Hao Yan, professor of biochemistry at Arizona State University and a senior scientist on the project, said.
"Combinations of different rationally designed nanorobots carrying various agents may help to accomplish the ultimate goal of cancer research: the eradication of solid tumours and vascularised metastases [secondary tumours hooked up to the bloodstream]."
For more than a decade, bioengineers have been building simple automata such as probes, walkers and motors out of DNA, which can be programmed with instructions like a crude biological computer.
Yan and his colleagues at the Chinese Academy of Sciences in Beijing have taken the idea a step further. Their nanorobots are "origami" sheets of DNA that roll up into tubes around a chemical payload. The tubes are tipped with "fasteners" that recognise and latch on to a chemical called nucleolin, which is abundant on the blood vessels that feed cancers but fairly rare on healthy tissue.
When they arrive at their destination they release their cargo, an enzyme known as thrombin, which prompts a blood clot and effectively strangles the tumour’s supply lines.
When the nanorobots were injected into the veins of mice with human breast cancer, the tumours typically grew to 0.3g, compared with three times that weight in mice that were injected with saltwater. The treated mice also survived for 39 days on average, 10 days longer than the untreated animals.
The therapy was even more effective in mice with melanoma. It doubled survival times and wiped out the tumours altogether in three out of eight mice. It also appeared to prevent the cancers from spreading.
Justine Alford, of Cancer Research UK, said DNA nanorobots could allow for more targeted treatment, reducing side effects, but blood-clotting drugs were unlikely to be the best use for the technology.
The study is published in Nature Biotechnology.