The authors exposed cells from a human malignant glioblastoma to RFR from a 2450 MHz signal. The SARs were in the wide range of 5-200 W/kg. Exposure to 2450 MHz at 50-200 W/kg causes temperature increases. Hence, appropriate heat control groups were also included in the range of 38-44°C. HSP70 and HSP27 were used as stress markers, as well as phosphorylated HSP27.

HSP&) increased in a time and dose-dependent manner at >50 W/kg SAR for 1-3hr. This was the same as changes in corresponding heat controls. HSP27 levels did not change significantly. However, phosphorylated HSP27 expression increased transiently at 100 and 200 W/kg to a greater extent than at 40-44°C.