Epidemiology suggests a possible relationship between exposure to power fre
quency magnetic fields (EMF) and breast cancer. One mechanism through which
EMF could stimulate breast cancer induction is via altered expression of o
ncogenes and/or tumor suppressor genes that regulate normal and neoplastic
growth. To evaluate the hypothesis that EMF action in the breast is mediate
d by alterations in gene expression, transcript levels of c-myc and a batte
ry of other cancer-associated genes were quantitated in human breast epithe
lial cells exposed to pure, linearly polarized 60 Hz EMF with low harmonic
distortion. HBL-100 cells and normal (non-transformed) human mammary epithe
lial cells were exposed to EMF flux densities of 0.1, 1.0 and 10.0 Gauss (G
) for periods ranging from 20 min to 24 h; concurrent sham controls were ex
posed to ambient fields (<0.001 G) only, Gene expression was quantitated us
ing ribonuclease protection assays. EMF exposure had no statistically signi
ficant effect on basal levels of c-myc transcripts in either human breast c
ell model, and had no effect on alterations in c-myc expression induced by
12-O-tetradecanoylphorbol-13-acetate. Transcript levels of c-erbB-2, p53, p
21, GADD45, bar, bcl-x, mcl-1, and c-fos were also unaffected by EMF exposu
re. These results suggest that EMF is unlikely to influence breast cancer i
nduction through a mechanism involving altered expression of these genes.