Comparison of cellular sensitivity to a split radiation dose and a combination of a single radiation dose and electromagnetic field exposure

Abstract

HIV-positive individuals, who are at high risk of developing cancers such as Kaposi’s sarcoma, tend to be more sensitive to ionizing radiation and are at a higher risk of develop-ing severe side effects during radiotherapy. To enhance therapeutic benefit in this patient cohort, new and noninvasive methods are needed to sensitize cancer cells and reduce therapeutic doses. To partially address this need, the effects of 100 and 1000 Hz electromagnetic fields (EMF) on the �radiosensitivity of Chinese hamster lung fibroblasts (V79) and human melanoma cells (MeWo) were evaluated, using the colony forming assay. The surviving fraction (SF) of V79 cells exposed to a 1000 Hz field for 30 min, followed by 2 Gy of X-rays 6 h later (SF = 0.6833 ± 0.0067), was significantly higher than that obtained when cells were irradiated twice with 1.5 Gy X-rays, 6 h apart (SF = 0.5620 ± 0.0026; P = 0.0008). On the other hand, the combination of EMF exposure and irradiation was more toxic (SF = 0.3350 ± 0.0050) in the melanoma cells than the split radiation treatment (SF = 0.3825 ± 0.0035; P = 0.0008). These data suggest that use of EMF may sig-nificantly reduce the total radiation dose during radiotherapy and minimize normal tissue toxicity without compromising tumor control.