Buried evidence
By Darrin S. Joy
It is tricky, but City of Hope cancer biologists say certain telltale clues in DNA might provide an answer, at least when it comes to lung cancer risk. Ahmad Besaratinia, Ph.D., and Gerd Pfeifer, Ph.D., the Lester M. and Irene C. Finkelstein Chair in Biology, published their ideas in the July 2008 issue of The Lancet Oncology.
Researchers generally believe that secondhand smoke exposure increases lung cancer risk by as much as double. Lung cancer can take a long time to develop, however. Over that time, people move and change friends, habits and workplaces, making it tough to pin down exactly how much secondhand smoke someone inhaled. They are probably exposed to other carcinogens, as well.
So Besaratinia and Pfeifer suggest a more direct approach: looking for particular changes in the DNA of people exposed to secondhand smoke. These changes, or biomarkers, come specifically from chemicals found in cigarette smoke. “We know of numerous changes to DNA that are directly related to cigarette smoke and can act as biomarkers for exposure,” said Pfeifer. By screening for those changes, they hope to better define the risk of developing lung cancer due to secondhand smoke exposure.
Pfeifer is keenly aware of how carcinogens in smoke influence lung cancer development. In the mid-1990s, he uncovered the first direct molecular evidence linking cigarette smoke to lung cancer mutations.
Unfortunately, DNA biomarkers to measure lung cancer risk are not quite ready for prime time yet.
Scientists have some screening methods that allow them to examine a large number of biological samples quickly, but they remain imperfect. As the technology evolves, though, screening lung tissue for secondhandsmoke- related biomarkers will become more practical, Pfeifer said.
In addition, the researchers suggest those same biomarkers might also be used to determine the best treatments for those who have lung cancer. They might even help predict the likelihood of a successful outcome after treatment — key information that could guide treatment decisions and preserve quality of life.
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