Effects of extremely low frequency electromagnetic field and cisplatin on mRNA levels of some DNA repair genes

•mRNA levels of seven genes involved in DNA repair pathways were evaluated.•The examined genes had tendency to be down-regulated in the cells treated with EMF.•GADD45A mRNA levels in cells co-treated with cisplatin (CDDP) + EMF were increased.•Co-treatment of CDDP + EMF enhances down-regulation of the genes of NHEJ pathway.•Elevation in IC50 of CDDP when cells co-treated with CDDP + EMF was observed.

AimsIt has been shown that exposure to extremely-low frequency (˂300 Hz) oscillating electromagnetic field (EMF) can affect gene expression. The effects of different exposure patterns of 50-Hz EMF and co-treatment of EMF plus cisplatin (CDDP) on mRNA levels of seven genes involved in DNA repair pathways (GADD45A, XRCC1, XRCC4, Ku70, Ku80, DNA-PKcs and LIG4) were evaluated.Main methodsTwo 50-Hz EMF intensities (0.25 and 0.50 mT), three exposure patterns (5 min field-on/5 min field-off, 15 min field-on/15 min field-off, 30 min field-on continuously) and two cell lines (MCF-7 and SH-SY5Y) were used. The mRNA levels were measured using quantitative real-time PCR.Key findingsThe examined genes had tendency to be down-regulated in MCF-7 cells treated with EMF. In the pattern of 15 min field-on/15 min field-off of the 0.50 mT EMF, no increase in mRNA levels were observed, but the mRNA levels of GADD45A, XRCC1, XRCC4, Ku80, Ku70, and LIG4 were down-regulated. A significant elevation in IC50 of CDDP was observed when MCF-7 and SH-SY5Y cells were co-treated with CDDP + EMF in comparison with the cells treated with CDDP alone. GADD45A mRNA levels in MCF-7 and SH-SY5Y cells co-treated with CDDP + EMF were increased and at the same time the mRNA levels of XRCC4, Ku80, Ku70 and DNA-PKcs were down-regulated.SignificancePresent study provides evidence that co-treatment of CDDP + EMF can enhance down-regulation of the genes involved in non-homologous end-joining pathway. It might be suggested that co-treatment of CDDP + EMF could be more promising for sensitizing cancer cells to DNA double strand breaks.