Effects of electromagnetic field, cisplatin and morphine on cytotoxicity and expression levels of DNA repair genes.

Morphine (Mor) is widely used as an analgesic drug in cancers and in combination with chemotherapy is known to have DNA damaging effects on non-targeted cell. This study surveyed the effect of Mor in combination with 50-Hz electromagnetic field (EMF) and co-treatment of cisplatin in combination with Mor and EMF on the expression of genes involved in DNA repair pathways. MCF-7 and SH-SY5Y cells were treated with 5.0 µM Mor and then exposed to 50-Hz 0.50 mT EMF in the intermittent pattern of 15 min field-on/15 min field-off. Gene expression, cisplatin and bleomycin cytotoxicity were measured using real-time PCR and MTT assay. Mor treated cells showed significant down-regulation of the examined genes, while in "Mor + EMF" treatments the genes were not significantly changed. IC50 of cisplatin was significantly elevated in both cell lines when co-treated with "Mor + EMF" compared with Mor treated cells. Non-homologous end joining (NHEJ) related genes were significantly decreased in co-treatment of cisplatin and "Mor + EMF" which led to bleomycin higher cytotoxicity in SH-SY5Y not in MCF-7. Our data is promising for providing a cell line-specific sensitization by combination of cisplatin and "Mor + EMF" treatment with local administration of double strand breaking agents.