Most experts agree that secondhand smoke is a health hazard that can lead to heart disease, lung damage and even cancer. Accurately measuring that hazard over a lifetime of exposure, though, is nearly impossible.
In the July issue of The Lancet Oncology, Ahmad Besaratinia, Ph.D., and Gerd Pfeifer, Ph.D., Lester M. and Irene C. Finkelstein Chair in Biology, suggest DNA biomarkers may provide an answer.
Researchers generally believe that secondhand smoke exposure increases lung cancer risk by as much as double. Lung cancer can take many years to develop, however. Over that time, specifics about secondhand smoke — the source, type and concentration in the air — can vary significantly. This makes a clear assessment of exposure difficult to pin down.
|Researchers are studying biomarkers to measure lung cancer risk from secondhand smoke. (Photo by Ahmad Besaratinia)|
“Essentially we have to rely on people’s memories of their exposure to secondhand smoke to estimate their risk,” said Pfeifer. “Obviously that is not the most reliable method.”
Over a lifetime, people are exposed to other carcinogens, too, further clouding the picture.
Besaratinia, an assistant research scientist in biology, and Pfeifer suggest looking for particular changes in the DNA of people exposed to secondhand smoke. These changes, or biomarkers, which come specifically from chemicals found in cigarette smoke, serve as telltale clues.
“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 can 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, current technological shortcomings make it tough to use DNA biomarkers to measure lung cancer risk today.
“There are high-throughput methods available, but their margins of error are still a bit too high,” he said. “But they’re coming along.”
High-throughput screening methods allow researchers to examine a large number of biological samples quickly.
As the technology evolves, screening lung tissue for secondhand smoke-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, and they might even help predict the likelihood of a successful outcome.