Enhancement of cytokine expression in transiently transfected cells by magnetoliposome mediated hyperthermia

We investigated the enhancement of cytokine expression by heat treatment in transiently transfected glioma cells. The cells were transfected with plasmid bearing the interferon (IFN)-beta gene under control of the MMTV promoter, which is inducible by glucocorticoid (dexamethasone). Then magnetite particles (10 nm diameter) as intracellular heating material were incorporated to the cells as the form of magnetoliposome. After 5 hours of incorporation, alternative magnetic field (384Oe, 118kHz) was applied for intracellular heating. IFN-beta secreted in the medium was assayed and its concentration was compared to the extracellular heating induced expression, bath in the presence and absence of dexamethasone. Higher IFN-beta concentration was detected in intracellular heating even at lower temperature, 39 degrees C, than 43 degrees C in extracellular heating. The lFN-beta expression level reached in the presence of dexamethasone was about three times higher than in the absence of inducer. In intracellular heating of 60 min, the surviving cell number reduced until 20%.