In newborns exposed to secondhand smoke, mutations in an important gene occur at a high rate, according to a pilot study in next month's Nature Medicine. The findings suggest that secondhand smoke may boost the risk for certain childhood cancers--but experts caution that the suspected link must be explored further in a larger study.
The evidence for cigarette smoke's impact on childhood cancer has been contradictory--some epidemiological studies indicate no added risk, while others show a clear increase for leukemia and lymphomas. Hoping to gather some genetic data, Barry Finette and his colleagues at the University of Vermont looked at DNA mutations in 24 infants, half of whom had been exposed to second hand smoke during pregnancy. (Tobacco carcinogens can pass through the placenta.) The researchers compared mutation rates in the HPRT gene, which is important for cell maintenance. "We use [this gene] as a window as to what could be going on in other parts of the chromosomes," Finette says. The group of infants exposed to secondhand smoke had three times as many of a HPRT deletion that is common in leukemia and lymphomas as the infants whose mothers were around nonsmokers. The mutation rate correlated roughly with the amount of a nicotine byproduct found in the newborns' blood.
The results are "incontrovertible evidence of the devastating genetic effects of tobacco smoke on the young," write Marco Pierotti and Gabriella Sozzi of the Istituto Nazionale Tumori in Milan, Italy, in an accompanying commentary. But the pair note that the small study should be broadened to a bigger one that measures smoke exposure levels and also looks at newborns whose mother's smoked during pregnancy.