[ある種のDNA修復遺伝子のmRNAレベルに対する超低周波電磁界およびシスプラチンの影響] med./bio.

The effects of co-exposure of two cancer cell lines to different 50 Hz magnetic fields and cisplatin on gene expression of genes involved in DNA repair should be investigated in view of a possible therapeutic use.

Two 50 Hz magnetic flux densities (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", continuously 30 min field "on") and two cell lines (MCF-7 and SHSY5Y) were used.
To test whether exposure to the magnetic field might sensitize cells to cisplatin, several groups were also tested in a co-exposure with cisplatin (15 µg/ml for MCF-7 cells, 4 µg/m for SH-SY5Y cells). To test whether co-exposure to the magnetic field and cisplatin might sensitize cells to double-strand breaks from, e.g., irradiation therapy, some co-exposed cells were treated with 1 µg/ml bleomycin, an irradiation mimicking drug.

• 無傷細胞／細胞培養
• MCF-7 (human breast cancer cell line) and SH-SY5Y (human neuroblastoma cell line)

A general trend towards a down-regulation of DNA repair involved genes was found in exposed cells compared to sham exposed cells. Intermittent exposure of field 5 (15 min field "on"/15 min field "off" with 0.5 mT) showed the most distinct results with significantly downregulated genes (GADD45A, XRCC1, XRCC4, Ku80, Ku70 and LIG4).
A significant elevation of the IC50 was found in cells co-exposed to the magnetic field and cisplatin (field 5) compared to a cisplatin treatment alone, indicating that magnetic field exposure did not sensitize cells to cisplatin.
However, co-exposure to the magnetic field and cisplatin significantly decreased the gene expressions of XRCC4, Ku80, Ku70 and DNA-PKcs (field 5) compared to sham exposed cells, while the gene expression of GADD45A was significantly downregulated. This was not observed in cells exposed to cisplatin alone. Cell viability was significantly reduced in a co-exposure to the magnetic field, cisplatin and bleomycin compared to a treatment with cisplatin and bleomycin alone, indicating that cells co-exposed to the magnetic field and cisplatin were sensitized to bleomycin.
The authors conclude that co-exposure to a 50 Hz magnetic field and cisplatin might downregulate genes involved in DNA repair, what could sensitize cancer cells to double-strand break-inducing drugs and irradiation therapy.