Drug resistance modification using pulsing electromagnetic field stimulation for multidrug resistant mouse osteosarcoma cell line

Multidrug resistance (MDR) is one of the major problems in osteosarcoma che motherapy. Therefore, methods of overcoming MDR are urgently needed. In thi s study, we investigated the effects of pulsing electromagnetic field stimu lation (PEMFs) on a MDX murine osteosarcoma cell line which strongly expres ses P-glycoprotein (P-gp). To assess the reversal effects of PEMFs on doxor ubicin (DOX) resistance, MTT assay was applied. Viable cells were assessed by the trypan blue exclusion test. Fluorescence intensity of DOX binding to nuclear DNA of each cell was measured using a cytofluorometer. Changes in P-gp expression in each cell wet e detected by the indirect immunofluoresce nce method using an antibody to Pgp. PEMFs increased DOX binding ability to nuclear DNA and inhibited cell growth, although it had no significant effe ct on P-gp expression. These findings indicated that PEMFs reversed the DOX resistance of the MOS/ADR1 cells by inhibiting P-gp, function. Tile result s suggested that PEMFs may be useful as a local treatment for MDX osteosarc oma.