Abstract:
Epidemiological studies have been provided evidence that exposure to electromagnetic fields (EMF) may be associated with an increased incidence of brain tumors, most notably astrocytomas. In this study we investigated whether exposure of human 1321N1 astrocytoma cells to 60Hz EMF would affect their proliferation. Proliferation was measured by 3H-thymidine incorporation, flow cytometry and cell counting. Exposure to EMF was carried out in a double-side incubator, using a one-coil Merritt system. EMP (1.2 G for 24h or 48h) increased proliferation of astrocytoma cells by 50-80% and strongly potentiated the effect of two mitogens, the muscarinic agonist carbachol and the phorbol ester TPA. GF 109203X, a rather specific PKC inhibitor, inhibited the effect of EMF on basal proliferation and its potentiation of TPA-stimulated proliferation. Down-regulation of PKC also blocked the proliferative effect of EMF, alone and in combination with mitogens. To test whether an applied magnetic field or the induced electric field was the operant field metric, exposure of EMF was also carried out utilizing plates of different sizes (radii of 3.2, 8.0, 17.5 mm). The effects of EMF on cell proliferation measured in these three types of plates were identical, suggesting that magnetic fields are responsible for the observed effects. These results indicate that EMF exposure can increase the proliferation of human astrocytoma cells and potentiate the effect of mitogens. Furthermore, initial evidence is provided that PKC may play a role in the effect of EMF on proliferation of these cells. These data may offer a biological basis for the observed epidemiological associations between EMF exposure and brain tumors.