Radiofrequency Field-Induced Radiosensitization Is Related to Reductions in Metabolic Activity

Although radiofrequency fields (RFFs) have been found to exhibit both radiosensitizing (enhancement of radiation) and radioprotective (mitigation of radiation) effects, mechanisms underlying these phenomena have not been clearly elucidated. Here, we use four human cell lines, namely, MeWo and Be11 (melanomas), DU145 (prostate carcinoma), and L132 (normal lung fibroblasts), to assess the role of RFF modulation of cellular metabolic activity in altering radiosensitivity. We measure radiosensitivity and metabolic activity using colony-forming and 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assays, respectively. Cell lines that are more radiosensitized by RFF exposure show larger reductions in metabolic activity, relative to radiation treatment alone, regardless of whether RFF exposure occurs before or after X-ray irradiation. The finding that surviving cells maintain elevated metabolic activity when treated with a combination of RFFs and X-rays suggests that changes in metabolic activity may be triggered by RFFs to support processes such as DNA repair and alteration of long-term cell survival. Modulation of cellular metabolic activity by RFFs may have important ramifications for moderating ionizing radiation–induced effects. This must be carefully considered if RFFs are to be applied as adjuvants in radiotherapy.