One of the problems with fighting cancer cells comes from the inability of drugs to distinguish between the cells that make up a tumor and the body’s own healthy ones. To get around this, the researchers decided not to kill off the cells themselves but the vessels supplying them with blood. And they did this using nanobots.
“We have developed the first fully autonomous, DNA robotic system for a very precise drug design and targeted cancer therapy,” says Hao Yan, co-author of the study published in Nature Biotechnology, in a statement. “Moreover, this technology is a strategy that can be used for many types of cancer, since all solid tumor-feeding blood vessels are essentially the same.”
The team took a rectangular piece of DNA origami sheet – measuring just 90 nanometers by 60 nanometers – and peppered it with a protein known as thrombin. This is a naturally occurring enzyme found in the body that induces clotting. The aim here is to deliver the protein to the blood vessels that supply the tumor with its nutrients and cut them off, effectively starving the cancerous cells.
The DNA origami sheet, with its associated clotting agent, is then folded up into a ring-like structure. The next step is to devise a way to deliver the nanobots to the site of the cancer, so that it doesn’t just start clotting the blood whereever it is. This is done by attaching another payload, this time a molecule known as a DNA aptamer.
The aptamer in question specifically targets a protein called nucleolin. While your body normally makes nucleolin, tumor endothelial cells also churn out the molecule in unusually high amounts. Crucially, at the same time, it is not found on the surface of healthy cells.
The nanobots were then injected into mouse models that had been specifically bred to mimic a variety of human cancers, such as lung and melanoma. Once into the circulatory system, they homed in on the tumor blood vessels, where the thrombin was then triggered and caused the blood to clot.
After doing this, the nanobots are cleared by the body, while the thrombosis – or blood clotting – in the tumors continued for three days following treatment, after which all blood vessels in the tumors showed signs of blockages. This resulted in the shrinking of tumors and doubling of the median survival time of the mice, as well as causing some to go into complete remission.
Not only did the bots show impressive results in targeting and tackling the cancer cells, but crucially they didn’t cause any side effects in the mice. This raises the hope that these kinds of nanobots could be put to use in humans much sooner than anticipated.