Cancer tumours in mice shrunk thanks to oxygen-sucking battery

Implanting an oxygen-consuming battery into mice with cancer caused their tumours to shrink or vanish in two weeks when used alongside an experimental class of cancer drugs.

As most tumours grow, they consume oxygen from the non-cancerous tissues around them so that the tumours’ cells become oxygen-free, or hypoxic. One class of drugs, called hypoxia-activated prodrugs (HAPs), seeks to exploit this trait by only killing cells that show hypoxia, so that healthy cells are less affected, reducing the treatment’s side effects. But no HAPs are approved for clinical use due to limited evidence into their effectiveness.

Now, Fan Zhang at Fudan University in Shanghai, China, and his colleagues have developed a self-charging, implanted battery that runs off salt water injected around it, causing the battery to produce very low voltage electricity and to consume oxygen. By creating a hypoxic environment, the battery should optimise the action of HAPs.

“The battery can cover the tumour and persistently consume the oxygen within it for more than 14 days, which is much longer than previous agents [that worked for] usually not more than two days,” says Zhang.

Zhang and his team implanted the battery into some of the armpits of 25 mice with breast cancer. Five received the working battery and HAP treatment. The remaining mice were organised into groups where they either received no treatment, HAP drugs only, an implanted battery that didn’t work or just the working battery, which can run for up to 500 hours in mouse tissue.

Fourteen days later, the tumours had shrunk by an average of 90 per cent across the five mice who received the working battery and HAP treatment, and they disappeared completely in four of these mice. The tumours remained the same size or grew in the other mice groups.

While the battery caused no safety concerns when used in mice, the safety bar is higher for people, so further research is required to ensure it is compatible with human tissue prior to testing in people, says Zhang.

Randall Johnson at the University of Cambridge says that inducing hypoxia in tumours can have downsides, such as an increased tendency for the cancer to spread elsewhere in the body. While this didn’t occur in the mice, the costs and benefits of the battery’s use in people would need to be assessed before any human treatment, he says.