A type of drug designed to stunt tumour growth has actually been found to fuel cancer if given at too low a dose.
UK scientists were investigating a kind of drug called an anti-angiogenesis, still under development, which hampers the growth of tumour blood vessels.
Avastin and Sutent, which act in a similar way, have been proven to work and were not covered in this research.
But cancer experts say the study in Nature Medicine could help make those drugs more effective.
The researchers focused on a drug called Cilengitide which is designed to prevent blood vessel cells sticking together and moving – an important part of angiogenesis.
Previous tests on people have found that a few patients with brain tumours benefited from high doses of the drug, but that it failed to work for most. In this research, tests carried out on mice showed that low doses of Cilengitide actually stimulated the growth of cancers.
Further investigation showed it did this by switching on a molecule called VEGFR2, which triggers the angiogenesis process.
That is significant because although when a patient is initially given a drug, its level in the blood rises quickly ensuring a big dose goes to the tumour, after a while levels start to fall as the body begins to deal with the drug.
This is likely to be why trials of the drug have shown such poor results.