Influence of X-rays on early response gene expression in rat astrocytes and brain tumour cell lines.

The effects of ionizing radiation on c-fos, c-jun and jun-B mRNA levels were determined in cultures of rat perinatal type 1 astrocytes and two rat brain tumour cell lines, 175A and 9L. In astrocyte cultures X-ray doses as low as 1 Gy induced the expression of c-fos and jun-B but had essentially no effect on c-jun. The maximum increase in expression was found 1 h after irradiation, which then rapidly returned to control levels. These findings suggest that astrocytes may play a role in mediating the radiation response of the central nervous system via X-ray-induced changes in gene expression. In contrast, doses of up to 20 Gy had no effect on c-fos, c-jun and jun-B mRNA levels in the two brain tumour cell lines. In addition, whereas 12-O-tetradecanoylphorbol-13-acetate induced the expression of these genes in astrocytes, it had little or no effect on fos or jun expression in 9L or 175A cells. These results suggest that the signal transduction pathways mediating radiation-induced gene expression may be different in normal astrocytes and brain tumour cells.