A compound derived from cruciferous vegetables such as cabbage, cauliflower and broccoli protected mice and rats from lethal doses of radiation, according to researchers from the Georgetown University Medical Centre (GUMC).

The study, published on 14 October 2013 in the Proceedings of the National Academy of Sciences (PNAS), suggests the compound, already shown to be safe for humans, may protect normal tissues during radiation therapy for cancer treatment and prevent or mitigate sickness caused by radiation exposure.

The compound, known as DIM (3.3’-diindolylmethane), previously has been found to have cancer preventative properties.

“DIM has been studied as a cancer prevention agent for years, but this is the first indication that DIM can also act as a radiation protector,” said Eliot Rosen MD, PhD, the study’s corresponding author, of Georgetown Lombardi Comprehensive Cancer Centre, a part of GUMC.

Study method

Researchers irradiated rats with lethal doses of gamma ray radiation. The animals were then treated with a daily injection of DIM for two weeks, starting 10 minutes after radiation exposure.

The result was “stunning”, according to the researchers.

“All of the untreated rats died, but well over half the DIM-treated animals remained alive 30 days after the radiation exposure,” Dr Rosen said.

The researchers noted that DIM also provided protection whether the first injection was administered 24 hours before or up to 24 hours after radiation exposure.

“We also showed that DIM protects the survival of lethally irradiated mice,” Dr Rosen said.

DIM also protected against side effects

Researchers said they also found that 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. Dr Rosen said the study points to two potential uses of the compound.

“DIM could protect normal tissues in patients receiving radiation therapy for cancer, but could also protect individuals from the lethal consequences of nuclear disaster,” Dr Rosen said.

Dr Rosen and study co-authors Saijun Fan, PhD, and Milton Brown, MD PhD, are co-inventors on a patent application that has been filed by Georgetown University related to the use of DIM and DIM-related compounds as radioprotectors.

The study was supported by US Public Health Service Grants, a grant from the Centre for Drug Discovery at Georgetown University, and other Georgetown funding.

Australian experts respond

Meanwhile, Australian experts have responded to the study with interest, saying that further research will be needed to determine the doses of DIM required for therapeutic use.

“There have been many attempts at developing radioprotective agents that protect normal tissues but not cancer,” said Professor Ian Olver, CEO of Cancer Council Australia. “Amifostine was one such drug which had some effect but itself had side effects which limited its use,” he said.

“Many drugs are derived from plants and it is not surprising that a chemical in vegetables could have these properties,” Professor Olver said.

Professor Michael Fenech, an expert from the CSIRO agreed that there was a need to develop effective countermeasures to the damaging effects of radiation therapy.

“The authors of the study showed that in the mouse DIM activates DNA repair in normal cells but not in cancer cells,” said Professor Fenech, Research Group and Stream leader for the CSIRO Animal, Food and Health Sciences. “This suggests that DIM could make it possible to protect normal tissue during radiation therapy and may also allow higher doses of radiation to be used to increase the certainty that the cancer is eliminated,” he said.

“Increasing the resistance of normal tissue against radiation-induced DNA damage may also be useful to minimise morbidity and death after radiation accidents or mitigate against the risk of cancer from exposure to other DNA-damaging agents,” Professor Fenech said. “It would be interesting to know what dose of DIM or broccoli is required to produce similar effects in humans,” he said.

The benefit of cruciferous vegetables in preventing cancer has been the subject of research in studies earlier in 2013 too. Australian Food News reported in August 2013 that other compounds found in broccoli can “retune” cellular processes that get disrupted as the body ages, and contribute to a reduced risk of cancer.