It’s not cool when a person sucks all the oxygen out of a room. When the battery does it with a tumor, that can be a good thing.
A study in mice shows that a small, self-charging battery wrapped around a tumor removes oxygen from the environment of cancer cells, boosting the power of some cancer treatments. Mice that had small batteries wrapped around their breast cancer tumors, along with the cancer treatment, showed a 90% reduction in tumor size Within two weeks, researchers reported on March 31 Science advances.
solid tumors such as Those that can develop into breast canceroften growing rapidly – so rapidly that the growth of the tumor is faster than its blood supply can support (SN: 5/10/17). This means that the center of many tumors can be hypoxic, with oxygen levels much lower than the surrounding tissues.
“Anoxia is a double-edged sword,” says materials scientist Yongyao Xia, who specializes in battery materials at Fudan University in Shanghai. Low oxygen levels in tumors It means that the body’s immune cells often cannot survive long enough to kill cancer cells (SN: 2/22/17). Hypoxic cells are also resistant to treatments such as radiotherapy and even conventional chemotherapy, as there is not enough blood flow to deliver a lethal dose, explains Fan Zhang, who studies biomedical materials at Fudan.
“On the other hand, it provides a target for the precise treatment of tumors,” Xia and Zhang write in the new paper.
Hypoxia can act as a beacon for chemicals called hypoxia-activated prodrugs. These are chemotherapy drugs bound by a chemical bond that ensures that the drug only becomes active in a low-oxygen environment, says Qing Zhang, a molecular biologist at the University of Texas Southwestern Medical Center at Dallas, who was not involved in the study.
But hypoxia-activated prodrugs do not show much benefit in clinical trials, perhaps in part because the solid tumors against which they are deployed are not uniformly hypoxic or hypoxic enough. Xia and Fan Zhang wanted to find a way to make the tumors more hypoxic, to give the initial drugs a better chance.
So the researchers and their colleagues deployed a small, flexible battery that could partially wrap around a tumor. The zinc electrode in the battery is charged by absorbing oxygen from the environment. It also produces highly reactive oxygen pairs that can damage DNA but is not a usable form of oxygen for cells.
By absorbing most of the available oxygen and producing lots of reactive oxygen pairs, the battery alone was able to shrink tumors in mice by up to 26 percent of their original size two weeks after implantation. When combined with a hypoxia-stimulating prodrug, the average tumor size shrank by 90 percent.
Subscribe to Science News
Get great science journalism, from the most trusted sources, delivered to your doorstep.
“I think the concept, the scientific basis, is solid,” Qing Zhang says. He says the results are encouraging, but very preliminary. Not only have the batteries been deployed in mice, but they have also been used against mouse breast cancer. “It should be tested in many models of breast cancer, and it should also be tested in other cancer models,” he says. And of course in humans.
Also, a 90% reduction in tumor volume is not a 100% reduction. “There’s still 10 percent left,” Qing Zhang says. If these cells survive, this may mean that they are resistant to hypoxia, and the tumor can grow again. As with many treatments, he says, it will likely be combined with other therapies to make sure the entire tumor is eliminated for good.
Xia, Fan Zhang, and their colleagues are already thinking about how to make a battery more flexible and powerful to work on human-sized tumors — using battery power to starve air-starved cancers.