Biological and technical variables in myc expression in HL60 cells exposed to 60 Hz electromagnetic fields

Abstract

The purpose of the present report is two-fold: first, to find an explanation for the inability of two groups of investigators, Lacy-Hulbert et al. and Saffer and Thurston [A. Lacy-Hulbert, R. Wilkins, T.R. Hesketh, J.C. Metcalfe, No effect of 60Hz electromagnetic fields on MYC or β-actin expression in human leukemic cells, Radiation Res. 144 (1995) 9–17; J.D. Saffer, S.J. Thurston, Short exposures to 60 Hz magnetic fields do not alter MYC expression in HL60 cells or Daudi cells, Radiation Res. 144 (1995) [18–25], to replicate our results, and second, to examine the broader issues involved in in vitro studies and replication in bioelectromagnetics. Replication experiments mandate that the precise cell type population be used and that the experimental protocol (i.e., exposure system, conditions of exposure, techniques for extraction and measurement) be followed exactly. By this criterion, the reported experiments of Lacy-Hulbert et al. and Saffer and Thurston were not replications. In this paper, we present replication experiments that again show a significant increase in c- myc transcript levels, although at a lower level. We also introduce variations from our protocol that were used in the reported ‘replication’ experiments. A major departure from the original experiments was use of different populations of HL60 cells; American Type Culture Collection (ATCC) as opposed to the original Columbia University Cancer Center (CUCC). The growth characteristics and responses to 12-0-tetra-decanoylphorbol-13-acetate (TPA) of the two cell populations showed significantly different reactivities. In line with these characteristics, c- myc increased in CUCC cells and did not increase in ATCC cells when stimulated by EM fields. We also compared other differences in protocol: SDS/phenol and guanidine/phenol RNA extraction procedures, the stability/variability of two housekeeping genes, β-2 μglobulin and GaPDH, as internal standards, sham-exposed controls versus inactive coil and double-wound coils versus single-wound coils. In all experiments, cell were shielded within mu metal containers during exposures. The shielding in one of the ‘replication’ studies, Lacy-Hulbert et al.'s, suggest that both experimental and control cells, which were side by side in the apparatus, were exposed to EM fields.