Key words: EMF, molecular biology, biological effects, tech support, research
Health issues concerning exposure to electric and magnetic fields (EMF) are discussed extensively in the news. There are a number of products under the regulatory authority of FDA which emit or utilize EMF radiation. These include electric blankets, video display terminals, and medical devices such as those used to treat non-unions (bone fractures), as well as wireless communications devices such as cellular telephones. Concern stems, in part, from epidemiological reports suggesting that EMF may play a role in cancer promotion. The program described below is part of a national research effort with contributions from NIH, CDC, DOE, and FDA. The data from this research will be used in a NIH risk analysis process leading to a Congressional report. This will place the FDA in a better position to evaluate claims of safety of products emitting EMF. The principal objectives of the program are (1) to establish and maintain a regional in vitro magnetic field exposure facility and (2) to perform studies which address the issue of reproducibility of published EMF biological effects. This program was supported by NIH and FDA. This program resulted in three published abstracts and six oral presentations at meetings during FY 97.
A state of the art regional EMF exposure facility has been developed. The two systems that comprise the core of this facility are capable of exposing samples to environmentally relevant extremely low frequency magnetic fields. They have been used for the work described below, as well as for research performed in collaboration with non-FDA investigators.
1. EMF and Gene Expression In Vitro
Key words: EMF, molecular biology, oncogenes, tech support, research
This project (see program description above) has addressed the issue of cancer promotion through investigation of the effects of 60 Hz EMF exposure on gene expression. Increased expression of genes related to cancer promotion would indicate a possible link to magnetic field exposure that has been suggested by some epidemiological findings. Specifically, the project includes a replication of the published experiments whose authors concluded that the expression of the MYC proto-oncogene is increased when cells are exposed to 60 Hz EMF. A detailed protocol for the gene expression replication study was developed in collaboration with the original investigators and peer reviewed by a panel of experts. Control baseline studies were performed to demonstrate that the methods used were capable of detecting reproducible changes in gene expression of greater than ten percent. Positive control studies using chemical agents known to cause gene induction demonstrated that the cells responded to a known tumor promoter and that the assay system was capable of making quantitative measurements of the resulting changes in gene expression. Replication experiments that assayed for specific gene expression by Northern blot analysis showed that MYC gene expression in EMF exposed cells was not distinguishable from that in sham exposed cells, suggesting that the exposure conditions defined by the original investigators are not sufficient to cause an EMF exposure-associated change in MYC gene expression.
To confirm and extend the results of these replication studies, changes in gene expression were investigated by applying novel assays to cell culture exposure protocols used for replication studies. Cellular RNA was isolated, reverse transcribed, and enzymatically amplified with a panel of arbitrary primers. Putative positive amplimers were cloned, sequenced, and prepared for use as probes to assay specific gene expression by hybridization analysis. HL60 cells were exposed to ELF-EMF or to TPA under the conditions previously used to test the response of MYC to these treatments. Several amplimers corresponding to putative differentially expressed genes were identified, isolated, and cloned. These clones will be analyzed by hybridization to cellular RNA to quantitate the ability of ELF EMF or TPA to regulate their expression. Preliminary work suggested that the molecular screen of cellular RNA described above may be suitable for identifying genes that respond to weak chemical or physical stimuli. The data from previously studied genes and gene products will be useful in interpreting the significance and implications of the effects of ELF EMF and TPA on these genes.
2. EMF and Enzyme Activity
Key words: EMF, biochemistry, ODC, tech support, research
This project (see program description above) has addressed the issue of cancer promotion through investigation of the effects of 60 Hz EMF exposure on the activity of ornithine decarboxylase (ODC), an important marker for cell proliferation and tumor promotion. Previous work in OST has indicated that it is in fact not possible to replicate one of the major reported effects of magnetic fields on ornithine decarboxylase (ODC). This earlier work had been cited by the 1996 National Academy of Sciences report on residential magnetic fields and childhood leukemia as one of the few, if not the only, in vitro biochemical endpoints which had been repeatedly shown to respond to magnetic field exposure. Our findings that the earlier data have not been replicated further strengthens the findings of the National Academy that magnetic field exposure is not a cause of childhood leukemia.
During the past year we have extended our earlier in vitro experiments on ODC activity to additional types of cells which have been reported to respond to magnetic field exposure. These other cell types also failed to show enhanced enzyme activity following 60 Hertz magnetic field exposure. We also conducted another series of exposures at the original investigators facilities to confirm results of exposures conducted at OST. Cells grown in OST laboratories were transported to CUA and prepared for exposure, followed by analysis at OST. There was no statistically significant difference between field-exposed and sham-exposed cells ODC activity. These results are consistent with our previously reported results that a 60 Hz magnetic field did not significantly enhance ODC activity in any of several different exposure systems. During FY98 we will participate in a collaborative effort to replicate a more recently reported finding that magnetic field exposure induces ornithine decarboxylase activity in rats exposed in vivo. The EMF-RAPID program will conduct the animal exposures at another facility and have tissues shipped to CDRH for enzyme analysis. CDRH is currently one of perhaps two or three facilities with the necessary expertise to process large enough numbers of samples to achieve statistical significance in an animal experiments
A summary of our work over the past two years was submitted to the EMF-RAPID Science Symposium held in March 1997 at NIEHS.