EFFECTS OF 50 HZ MAGNETIC-FIELDS ON C-MYC TRANSCRIPT LEVELS IN NONSYNCHRONIZED AND SYNCHRONIZED HUMAN-CELLS

The effects of 50 Hz electromagnetic fields (EMFs) on the expression o f the c-myc oncogene, known to be involved in normal cell proliferatio n and possibly also in tumor processes, were investigated in nonsynchr onized human lymphoid cells immortalized by Epstein-Barr virus. Viral injury to such cells makes them a good model for exploring the possibl e cancer-promoting effects of 50 Hz magnetic fields. Parallel experime nts were conducted on human HL60 leukemic cells. Cells were exposed to sinusoidal 50 Hz EMFs at 10 mu T or 1 mT for 20 min, 1 h, 24 h, or 72 h. Exposure was performed either immediately after refeeding or 1.5 h after refeeding. C-myc transcript values were assessed by Northern bl ot analysis and normalized to those of the noninducible gene GaPDH. No statistically significant difference between the c-myc transcript lev els of control and exposed cells was found in lymphoid or leukemic cel ls under our experimental conditions, either after short exposures of 20 min and 1 h or after longer exposures of 24 and 72 h. Other experim ents were carried out with pseudosynchronized cells in an attempt to e stablish whether cells were especially sensitive to 50 Hz magnetic fie ld exposure in any particular phase of the cell cycle. Accordingly, ce lls were pseudosynchronized in G0/G1 by serum deprivation and exposed for 20 min to a 50 Hz magnetic field, at 10 mu T for lymphoid cells an d 1 mT for HL60 cells. No significant difference was observed between the c-myc transcript levels of control and exposed cells for either of the synchronized cell types. These results for synchronized cells cor related with those for nonsynchronized cells. (C) 1995 Wiley-Liss, Inc .