Pôde a radiação médica danificar mais do que o DNA?
por Brendon Nafziger, DOTmed News Associate Editor | February 04, 2010
It's not just DNA,
but surrounding proteins
that determine
gene expression
but surrounding proteins
that determine
gene expression
As scientists wrangle over how significantly low-dose radiation from X-rays and CT scans might increase cancer risks, a radiologist wonders if they have neglected another possible danger: adverse epigenetic effects.
Large blasts of ionizing radiation are known to scramble cellular DNA, creating mutations. But not much has been done to study radiation's effects -- especially low doses of radiation, the kind released in medical imaging -- on the proteins that surround DNA and aid in gene expression, according to Dr. Shella Farooki, a radiologist at Columbus Radiology Corporation in Columbus, Ohio, writing in the current issue of the Journal of the American College of Radiology.
"Lately, as radiologists, we've been under the gun to address our utilization of CT and fluoroscopy and nuclear medicine, and there has been a lot of media attention to radiation exposure and overdose. But I wonder if there's any relationship between epigenetics and CT," Dr. Farooki tells DOTmed News.
Epigenetics is the study of non-DNA-based control of gene expression and heredity, mediated by complicated biochemical processes, such as methylation and the activity of DNA-supporting proteins known as histones.
Some of its effects are startling. Research conducted by Dr. Randy Jirtle, a professor of radiation oncology at Duke University Medical Center, has shown that a special diet fed to mice can actually cause genetically identical offspring, in essence, mouse twins, to have different color fur, Dr. Farooki notes.
And a long-running research program involving Dutch survivors of a 1944 famine found that not only were the children of women who endured the harsh wartime conditions underweight when compared with control subjects, even their children were, hinting at a possible non-genetic hereditary mechanism spanning generations.
Radiation has also been found to have a role in epigenetic causes of cancer. In her article, Dr. Farooki cites a 2004 study showing how plutonium might have caused glandular cancers in Russian workers exposed to the radioactive substance through DNA methylation that knocked out a tumor-suppressing gene.
Part of the complexity of the research is that the biological effects of low-dose radiation are not well established. Although many medical organizations and the government subscribe, at least on paper, to the linear no-threshold model, which argues that any amount of ionizing radiation increases one's risk for cancer by at least some conceivably measurable amount, some scientists suspect the risks of low-doses of radiation could be negligible.
And in fact, Dr. Jirtle tells DOTmed News that some early, unpublished research suggests low-doses of radiation could have protective epigenetic effects, by "stabilizing the epigenome."
In any event, epigenetics research is in for a cash bonanza. In 2008, the National Institutes of Health earmarked $190 million to fund projects that will help determine what role epigenetics might play in disease, aging and development. And Dr. Farooki hopes new research could make radiologists start to take notice of a field she thinks most haven't looked into.
Large blasts of ionizing radiation are known to scramble cellular DNA, creating mutations. But not much has been done to study radiation's effects -- especially low doses of radiation, the kind released in medical imaging -- on the proteins that surround DNA and aid in gene expression, according to Dr. Shella Farooki, a radiologist at Columbus Radiology Corporation in Columbus, Ohio, writing in the current issue of the Journal of the American College of Radiology.
"Lately, as radiologists, we've been under the gun to address our utilization of CT and fluoroscopy and nuclear medicine, and there has been a lot of media attention to radiation exposure and overdose. But I wonder if there's any relationship between epigenetics and CT," Dr. Farooki tells DOTmed News.
Epigenetics is the study of non-DNA-based control of gene expression and heredity, mediated by complicated biochemical processes, such as methylation and the activity of DNA-supporting proteins known as histones.
Some of its effects are startling. Research conducted by Dr. Randy Jirtle, a professor of radiation oncology at Duke University Medical Center, has shown that a special diet fed to mice can actually cause genetically identical offspring, in essence, mouse twins, to have different color fur, Dr. Farooki notes.
And a long-running research program involving Dutch survivors of a 1944 famine found that not only were the children of women who endured the harsh wartime conditions underweight when compared with control subjects, even their children were, hinting at a possible non-genetic hereditary mechanism spanning generations.
Radiation has also been found to have a role in epigenetic causes of cancer. In her article, Dr. Farooki cites a 2004 study showing how plutonium might have caused glandular cancers in Russian workers exposed to the radioactive substance through DNA methylation that knocked out a tumor-suppressing gene.
Part of the complexity of the research is that the biological effects of low-dose radiation are not well established. Although many medical organizations and the government subscribe, at least on paper, to the linear no-threshold model, which argues that any amount of ionizing radiation increases one's risk for cancer by at least some conceivably measurable amount, some scientists suspect the risks of low-doses of radiation could be negligible.
And in fact, Dr. Jirtle tells DOTmed News that some early, unpublished research suggests low-doses of radiation could have protective epigenetic effects, by "stabilizing the epigenome."
In any event, epigenetics research is in for a cash bonanza. In 2008, the National Institutes of Health earmarked $190 million to fund projects that will help determine what role epigenetics might play in disease, aging and development. And Dr. Farooki hopes new research could make radiologists start to take notice of a field she thinks most haven't looked into.
