Scientists have used a version of the anthrax toxin to kill tumours in mice. The toxin was so effective that after just one treatment, tumours were reduced in size by up to 92%. The technique has been developed by researchers from the US National Institutes of Health. It works by targeting a protein called urokinase which is produced in high levels by cancerous cells. The researchers genetically altered the structure of the anthrax toxin so it only invaded cells that produced high levels of urokinase. Different tumour types The toxin effectively killed several types of tumour cells, without causing any apparent damage to normal tissue. Tumour cells began dying just 12 hours after the first treatment. Two treatment cycles were enough to completely obliterate 88% of a type of tumour called a fibrosarcoma. It also knocked out 17% of a second type of tumour called a melanoma.
However, the toxin did not damage skin cells or hair follicles surrounding the tumour – suggesting that the toxin is highly selective, and may not lead to the severe side effects sometimes associated with alternative treatments. The researchers stress that further research is needed to determine if the engineered anthrax toxin will have similar effects in humans. Lead researcher Dr Steve Leppla told BBC News Online: “The fact that our cytotoxin can successfully kill several different solid tumours suggests it may be even better on leukemias, where the toxin has an easier time reaching every tumour cell. “We are testing that now.” Dr Elaine Vickers, of Cancer Research UK, described the research as very interesting, but warned that it was still at an early stage.
She said more work was needed to discover whether the technique worked in humans, and to confirm that it did not damage healthy cells. “Molecules that are over-produced by cancer cells are very interesting as targets for developing new cancer treatments, hopefully with fewer of the side-effects associated with more conventional therapies. “However, it is essential that the molecule targeted by the treatment is exclusively over-produced by cancer cells to avoid damage to healthy tissue. “This is particularly important if a potent toxin, such as the anthrax toxin being investigated in this research, is being used to kill the cancer cells.” The research is published in the Proceedings of the National Academy of Sciences.