Interferon-modification of the in vitro radiation response of cultured human KNS-42 cells

Abstract

The efficacy of combined interferon radiation therapy in cultured human KNS-42 glioma cells was examined. Beta type human fibroblast interferon inhibited the multiplication of KNS-42 cells in a dose-dependent manner. The inhibitory effect was thought to be due to supression of the cells entering the S-phase. KNS-42 cells were treated with interferon before or after irradiation. The effect of the treatments was assayed by growth and survival curves. According to a cell growth analysis, the combined treatment had a greater anti-proliferative effect than the radiation or the interferon treatment alone. When interferon was given before irradiation, it tended to reduce the shoulder of the X-ray survival curve in a dose-dependent manner until the shoulder totally disappeared. The slope itself, however, was only moderately affected by interferon. The mechanism of this synergistic interaction between interferon and X-rays was possibly due to a partial synchronizing effect of interferon on the cells by blocking them in a G1S boundary phase, the radiosensitive stage of the cell cycle. When interferon was given immediately after irradiation, it tended to reduce the slope in a dose-dependent manner. The shoulder disappeared almost totally even with a low dose of interferon. These results suggest that interferon may be useful as a radiosensitizing agent in tumor therapy.