Leukaemia is currently treated with chemotherapy
Scientists at the University of Dundee have discovered how arsenic works as an effective treatment for leukaemia.
According to a report in Nature Cell Biology, patients with acute promyelocytic leukaemia can be treated with arsenic.
Now scientists have solved the mystery of how arsenic can treat cancer, more treatments with fewer side effects are likely to be developed.
Cancer Research UK's Professor Ronald Hay compiled the report.
He 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 helped 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."