Electromagnetic fields may trigger enzymes.

Though numerous epidemiological studies have hinted that exposure to the electromagnetic fields (EMFS) associated with power lines, home wiring, and appliances may cause leukemia or other malignancies, researchers have lacked any explanation of how EMFS could produce such effects. The fields seem incapable of delivering enough energy into the body to damage DNA or bring about other harmful changes.

Now, in a pair of studies, an international team reports what may be the first Emf-triggered change in a cascade of events that could result in cancer. The cascade begins with the activation of enzymes -- tyrosine kinases -- produced by tumor-promoting genes.

For about 6 years, pediatric oncologist Fatih M. Uckun of the Wayne Hughes Institute in St. Paul, Minn., reviewed radiation research proposals, including those focusing on EMFS, from people seeking grant money from the National Institutes of Health. He was highly skeptical of the link between EMFS and cancer. Without a mechanism for suspected EMF risks, he says, "I had thought it was voodoo."

That assessment is now coming back to haunt him, he says. His latest test-tube studies show that magnetic fields with a frequency of 60 hertz and a strength of 1 gauss -- on the high end of exposures that might be encountered in the home or workplace -- trigger a cascade of enzyme-driven cell-signaling events. These short-distance communications serve as a means by which cells can relay operational directions to their DNA.

A year ago, Uckun and his team reported that ionizing radiation could prompt cell membranes to initiate a similar signaling cascade. Those data, he says, suggested that events triggered by the enzyme tyrosine kinase "are responsible for the final DNA damage that ionizing radiation induces." Out of curiosity, the team decided to look at EMFS, expecting that they would prove ineffective.

Instead, the EMFS activated a tyrosine kinase dangling from the inner surface of the cell membrane. By alternately removing and inserting the gene that makes the enzyme, Uckun and his colleagues report in the Feb. 13 Journal of Biological Chemistry, they showed that cells exhibit a response to EMFs only when the kinase is present. This suggests that activation of the enzyme represents the initial manifestation of EMFS' biological influence, Uckun says.

In a second report, slated to appear in the journal in April, the team details the cascade of events triggered by EMFS' activation of that enzyme. It includes the turning on of a second tyrosine kinase, known as BTK. Studies in people have shown that excessive activation of BTK can lead to leukemia, lymphomas, and other cancers, Uckun observes.

Because "you don't have any hormone production without activation of tyrosine kinases," Uckun says, the new findings may also explain provocative hormonal perturbations linked to EMF exposures (SN: 1/10/98, p. 29).

"Uckun's work provides key information for beginning to understand how magnetic field exposure may lead to biological effects," observes Jerry L. Phillips of the Veterans Administration Medical Center in Loma Linda, Calif. However, he adds, "it does not tell us how magneticfield exposure may lead to leukemia or other cancers" because the cells studied "were already cancerous."

Clearly, "if the effects can be repeated, they are significant," says Steven C. Miller of SRI international in Menlo Park, Calif. While he has attempted to copy Uckun's study, to date he has "gotten no [EMF] effect." Miller says the two labs should now work closely to resolve their contradictory findings.