Analysis Of Candidate Responsive Genes To GSM 1800 MHz Radiofrequency Electromagnetic Fields

The human exposure level to radiofrequency (RF) radiation has increased during recent years due to the rapid development of mobile communication and widespread use of mobile phone (sometimes called cellular phone). Public concerns have raised about the possible health effects of mobile phone radiation. Epidemiological studies have indicated an association between cell phone use and the risk of human cancers or non-cancer diseases (e.g. cataracts, chronic neural diseases), but an exclusive correlation has not been well established. Similarly, results of in vivo and in vitro studies are contentious and contradictory data still remain in the literature. Therefore it has been difficult to elucidate the role of RF EMF in possible health hazards, partly attributing to the inconsistent results, and more importantly, the unknown mechanism of RF EMF interacting with organisms. Thus, the RF research has been assigned as a priority by World Health Organization (WHO) since 2003 (see http://www.who.int/peh-emf/research/rfD3/en/). We reason that it is more important to investigate the bio-effects and underlying mechanism of RF radiation.Recently, high-throughput screening techniques (HTSTs), such as transcriptomics and proteomics, have been proposed as a practical approach to non-selectively gather information about the effects of environmental stimuli on gene transcription and protein expression. HTSTs could be used to rapidly identify a broad variety of potential molecular targets of RF EMF and generate a variety of biological end-points for further analyses. This approach seems to be particularly useful for elucidating RF EMF health hazard issue because it might reveal effects that are not possible to predict, based on the present very limited knowledge about the biological effects of RF EMF.Previously, we employed Genechip approach to investigate whether GSM 1800 MHz RF EMF can change gene expression in human breast cancer cells (MCF-7) and Saccharomyces cerevisia cells and to screen possible RF EMF responsive genes, and several RF EMF candidate response genes were identified after Genechip data analysis. In the present study, fluorescence real time quantitative reverse transcription polymerase chain reaction (RT-PCR) was used to validate these differentially expressed genes identified by Genechip analysis and ultimately to evaluate the effects of RF EMF on gene expression in these two cells.Part I. Gene Expression Analysis of MCF-7 Cells Exposed to GSM 1800 MHz RFEMFIn our pievious study, In vitro subcultured MCF-7 cells were intermittently (5 min on/10 min off) exposed or sham-exposed to GSM 1800 MHz RF EMF, which was modulated by 217 Hz EMF, for 24 h at an average specific absorption rate (SAR) of 3.5 W/kg. Affymetrix Human Genome U133A Genechip was applied to examine the change of gene expression profile according to the manufacturer's instructions. Data was analyzed by Affymetrix Microarray Suite 5.0 (MAS 5.0) and Affymetrix Data Mining Tool 3.0 (DMT 3.0). Five up-regulated genes were screened out after exposure to RF EMF at SAR of 3.5 W/kg. In order to confirm the Genechip analysis results,quantitative reverse transcription polymerase chain reaction (RT-PCR) was used to further validate the differentially expressed genes identified by Genechip analysis. The fluorescence real time quantitative RT-PCR analysis showed that the average fold change of six repeated analyses for each differentially expressed gene were near to 1.00, and no significant difference in each gene expression was found between RF EMF exposure and sham exposure groups, which suggested that these five genes could not be confirmed by fluorescence real time quantitative RT-PCR. In conclusion, the present study does not provide clear evidence that RF EMF exposure can distinctly change gene expression in MCF-7 cells under current experiment conditions.Part II. Gene Expression Analysis of Saccharomyces Cerevisiae Cells exposed to GSM 1800 MHz RF EMFPreviously, to investigate the effect of 217 Hz EMF modulated GSM 1800 MHz RF EMF exposure on gene expression profile of model organism Saccharomyces Cerevisiae and to screen its RF EMF responsive genes, Saccharomyces Cerevisiae cells were intermittently (5 min on/10 min off) exposed or sham-exposed to GSM 1800 MHz RF EMF for 6 h at an average specific absorption rate (SAR) of 3.5 W/kg. Affymetrix Yeast Genome S98 Genechip was applied to examine the effect of RF EMF on yeast gene expression profile according to the manufacturer's instruction. Data was analyzed by Affymetrix GeneChip Operating Software 1.0 (GCOS 1.0) and Affymetrix data mining tool 3.0 (DMT 3.0), and 40 genes with 100% consistency expression change were found after exposure to RF EMF, in which 27 genes were up regulated and 13 genes were down regulated. In the present study, fluorescence real time quantitative RT-PCR was used to confirm Genechip analysis result and to validate the differentially expressed genes responding to RF EMF exposure in Saccharomyces Cerevisiae cells. Twenty-four of up regulated genes screened by Genechip analysis were subjected to the RT-PCR anslysis. The obtained result showedGenechip analysis were subjected to the RT-PCR anslysis. The obtained result showed that the average fold change of three repeated analyses for each differentially expressed gene were near to 1.00, and no significant difference in each gene expression was found between RF EMF exposure and sham exposure groups, although slight changes in gene expression for several of them were found in single independent experiment. Generally, these RF EMF candidate responsive genes could not be confirmed by fluorescence real time quantitative RT-PCR. We conclude that the present study does not provide clear evidence that RF EMF exposure can distinctly and repeatedly change gene expression of Saccharomyces Cerevisiae.