Treatment shields healthy cells while letting tumors die
The key to surviving a nuclear disaster may lie in Brussels sprouts: A compound derived from these and other hardy vegetables protected rodents from lethal doses of radiation in recent experiments.
The compound, 3,3’-diindolylmethane or DIM, gets produced in the stomach after people eat cruciferous vegetables such as broccoli, Brussels sprouts or cabbage. Well known for fighting cancer in animal experiments, the compound is available as a dietary supplement. Even the Dr. Oz Show has highlighted DIM’s potential anticancer benefits.
In 2009, clinical researchers Eliot Rosen, Saijun Fan and colleagues at Georgetown University in Washington, D.C., found that the compound does something more: It can shield cells from chemical damage wrought by hydrogen peroxide, Rosen says.
Rosen and colleagues next decided to see if DIM protects against ionizing radiation, the kind released in nuclear disasters and that cancer patients receive to wipe out tumors. The effects of cancer radiation treatments often damage healthy cells, and Rosen wondered whether DIM could protect them. What’s more, DIM seemed promising because no effective treatments exist to stave off sickness in the aftermath of a nuclear disaster.
The researchers zapped rats with a hefty dose of gamma rays, a type of ionizing radiation. The dose was enough to kill the animals within 10 days. When the researchers injected a group of the rodents with daily doses of DIM starting two hours after the radiation exposure, 60 percent of the animals survived for at least 30 days and appeared healthy. Thirty percent survived when the researchers held off on DIM injections until 24 hours after exposure. The team reports the results October 14 in the Proceedings of the National Academy of Sciences.
The team found that in healthy cells, DIM boosted cellular responses that repair damage to DNA, one of the common effects of radiation on the cell. Luckily, DIM’s protective shield didn’t extend to every cell type: When the researchers implanted human breast cancer cells into the rodents and hit the animals with radiation, DIM treatment did nothing to protect the tumors. DIM’s protective powers may have been lost on the tumor cells, Rosen says, because DNA repair signals in the tumor cells were already abnormal.
Rosen hopes DIM will fail to protect other tumors as well. If so, cancer patients could take DIM to prevent side effects of radiation therapy. Rosen says that patients would probably need to take DIM as an injection or in pill form, rather than scarfing down enormous quantities of broccoli, to make enough of the compound in their bodies.
DIM’s protective effects against whole body radiation are impressive, says Gary Firestone of the University of California, Berkeley, who has spent decades studying the anticancer effects of compounds from cruciferous vegetables. If DIM also gives other types of tumors the cold shoulder, Firestone foresees using the compound to protect cancer patients from the side-effects of treatment. “The next step is clearly to see whether it works in humans.”
And Eric Hall, a radiation biologist from Columbia University, calls the results “almost too good to be true.” He wants to see the experiments replicated.
Because DIM protected animals even though they received it after radiation exposure, Hall says the compound could theoretically work in the aftermath of a nuclear accident or attack. “There are excellent protectors available if you take them beforehand,” Hall says, “but that won’t work unless you know you’ll be irradiated ahead of time.”
S. Fan et al. DIM (3,3’-diindolylmethane) confers protection against ionizing radiation by a unique mechanism. Proceedings of the National Academy of Sciences. Published online October 14, 2013. doi:10.1073/pnas.1308206110.
L. Sanders. Microbe’s survival manual. Science News Online. September 3, 2010.
S. Fan et al. Low concentrations of diindolylmethane, a metabolite of indole-3-carbinol, protect against oxidative stress in a BRCA1-dependent manner. Cancer Research, Vol. 69, August 1, 2009, p. 6083. doi: 10.1158/0008-5472.CAN-08-3309