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The discovery by University of Wisconsin researchers of genes that are necessary for surviving high levels of radiation has potentially big implications for imaging and radiation therapy.

The researchers developed a highly radiation–resistant strain of Escherichia coli by exposing cultures of the bacterium to extreme doses of radiation. “We blasted the cultures until 99 percent of the bacteria were dead,” said Michael M. Cox, PhD, assistant chair of the Wisconsin biochemistry department. “Then we’d grow up the survivors and blast them again. We did that 20 times.” Cox was quoted in a university news release.

The researchers then identified which genes were involved in resistance to ionizing radiation. They found 46—all of them genes that exist in wild E.coli bacteria, not radiation-induced mutations. “The results reinforce the notion that survival after high doses of ionizing radiation does not depend on a single mechanism or process,” Dr. Cox and four co-authors wrote in an article about the research that was published online Monday in Journal of Bacteriology.

In a news release from the American Society for Microbiology, publisher of the journal, Dr. Cox described the breadth of the genes involved:

We established a role for genes involved in processes as diverse as central metabolism and the synthesis and maintenance of the cell wall in radiation survival. Perhaps most important, we identified eight genes of unknown function that play substantial roles in radiation survival.

One gene has a role in repairing double-strand breaks in DNA. “The gene is related to a human gene called XPB,” Dr. Cox said, “and it may help elucidate some key DNA repair pathways in humans that help protect us from cancer.”

If radiation damage to human cells could be repaired, then radiation dosages from imaging would be much less of a concern than they are now. And what if we could turn off radiation-resistance genes in cancer cells but preserve or even strengthen their activity in surrounding healthy tissue? That could vastly increase the effectiveness and safety of radiation therapy.

“Our understanding of how cells deal with ionizing radiation is very rudimentary,” Dr. Cox said. More research along the lines that he and his colleagues are pursuing could have considerable impact on radiology and radiation oncology. Stay tuned.

Related CME seminar (up to 42.75 AMA PRA Category 1 credits™): UCSF Radiology Review: Comprehensive Imaging


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