Inhibition of DNA synthesis and enhancement of the uptake and action of methotrexate by low-power-density microwave radiation in L1210 leukemia cells med./bio.

To study the effects of low power density microwave radiation (continuous and pulsed wave) on the uptake and action of methotrexate (MTX), the inhibtion of DNA synthesis in murine leukemia cells in vitro, and the MTX treatment of mice bearing this leukemia.

• intact cell/cell culture
• L1210 (murine leukemia cells)
• animal
• mouse/DBA/2 (L1210 cells were passaged in these mice)
• whole body

MTX concentrations of 0.2 µM and irradiation times of 20 min, the authors found that continuous wave low power density microwave exposure enhances the uptake of [³H]MTX as compared to nonirradiated controls. The enhancement is observed in only a small range of power densities (5 to 25 mW/cm²). Microwave exposure alone has an inhibitory effect on the [³H]dUrd incorporation into DNA. Compared to cell suspensions treated with MTX alone, groups treated with microwave irradiation followed by MTX exhibit an augmentation of inhibition of DNA synthesis. Combined treatment of L1210-bearing mice with microwave irradiation and MTX in vivo prolonged the duration of survival over that mice treated with MTX alone. This indicates a greater killing of leukemia cells. The results suggest that the therapeutic index of MTX may be improved by the use of microwave irradiation at low power densities.