Scientists solve arsenic's cancer paradox

Cancer Research UK scientists have discovered how arsenic works as an effective treatment for leukaemia - according to a report in Nature Cell Biology.

Patients with a certain kind of leukaemia - acute promyelocytic leukaemia -can be successfully treated with arsenic, but scientists didn't know how the process worked.

Now scientists have solved the mystery of how arsenic can treat cancer, more targeted treatments with fewer side effects are likely to be developed.

Lead author, Cancer Research UK's Professor Ronald Hay based at the University of Dundee, said: "Our discovery is key to understanding how we can enhance the anti-cancer properties of this poison.

"Knowing the specific molecules involved allows us to now work on creating more targeted and effective cancer drugs with fewer side effects."

The scientists watched the drug at work in animal cells. They modified some cells to remove certain proteins and discovered the drug had different effects.

They found that arsenic helps molecules called SUMO stick onto proteins involved in leukaemia. An enzyme called RNF4 hunts down SUMO and breaks down the cancer-causing proteins.

Cancer Research UK's director of cancer information, Dr Lesley Walker, said: "Discovering which molecules are involved in this process is an exciting step forward in understanding this complex paradox - how can a chemical that causes cancer also cure it?

"It's a great piece of science that will hopefully lead to the development of drugs that home in on specific cancer-causing proteins to beat the disease."

For media enquiries please contact the Cancer Research UK press office on 020 7061 8300 or, out-of-hours, the duty press officer on 07050 264 059.

Notes to editors:

*RNF4 is a poly-SUMO-specific E3 ubiquitin ligase required for arsenic-induced PML degradation. Tatham et al. 2008. Nature Cell Biology.

** Arsenic trioxide (ATO) is used to treat acute promyelocytic leukaemia – a rare form of leukaemia. Around 60 cases are diagnosed each year in England. It is used in patients who have relapsed or are resistant to other drugs.

Arsenic is one of the most dangerous chemicals in cigarettes, causing lung cancer in smokers.

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