The compound may protect people under radiation therapy and those exposed to radiation from a nuclear accident

A naturally occurring molecule has been shown in laboratory tests to protect mice and rats from lethal doses of radiation. Scientists hope that this substance will be similarly beneficial for people who have to undergo radiation therapy for cancer as well as those who get exposed to radiation from a nuclear accident.

A diet rich in vegetables like cabbage, cauliflower and broccoli has been linked to a lower risk of several sorts of cancer. These vegetables contain a compound, indole-3-carbinol, which is broken down in the stomach to DIM (3,3'-diindolylmethane). Both compounds are being studied for their cancer prevention properties.

Eliot M. Rosen of the Georgetown University Medical Centre in the U.S. and his colleagues have now examined whether DIM could have protective effects against radiation.

Two groups of mice were exposed to lethal doses of gamma ray radiation. One group received daily injections of DIM for two weeks, with the first dose being given 10 minutes after irradiation, and 60 per cent of those mice were still alive 30 days later. The other group did not get DIM and all the mice died within 10 days of receiving radiation, the scientists reported in a paper just out in the Proceedings of the National Academy of Sciences (PNAS).

When the first dose of DIM was given one day before the administration of radiation, a much lower dose sufficed to protect the mice.

In addition, irradiated mice treated with DIM had less reduction in red blood cells, white blood cells and platelets — side effects often seen in patients undergoing radiation treatment for cancer, observed Dr. Rosen in a press release issued by the university. In several experiments, rats that survived for more than 30 days following radiation and DIM treatment were monitored for longer periods of time. There was little or no falloff in survival up to three months, and the animals appeared healthy and regained their original weight.

The scientists also showed that DIM could protect two noncancerous human breast cell lines from the ravages of radiation. The molecule caused rapid activation of an enzyme, ataxia telangiectasia mutated, that regulates cellular responses to DNA damage and oxidative stress, they noted in the paper. But, significantly, when human breast cancer cells were grafted on to immune-deficient mice, DIM did not affect the extent to which the resulting tumours shrank when irradiated.

“We haven't tested enough cell lines to be able to say that DIM does not protect tumours against radiation,” cautioned Dr. Rosen in an email. “This requires further study.” If true, the reason might be that many tumours have defective DNA repair mechanisms.

More animal studies were needed to move the project forward, he went on to point out. The best route for administering DIM – such as whether it should be given orally or as injections – had to be worked out.

Georgetown University has filed a patent application on the use of DIM and DIM-related compounds for radiation protection.

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