Interferon-beta inhibits proliferation and progression through S phase of the cell cycle in five glioma cell lines

The growth inhibitory effect of IFN-beta was evaluated in 5 human glioma cell lines (AO2V4, GJC, GJR, NN and NNR) and in normal astrocyte cultures (SC and TM). All 5 glioma cell lines showed an anti-proliferative response to IFN-beta whereas normal glial cells were non-responsive. IFN-beta at 10, 100 and 500 U/ml lead to a 30%, 70% and 80% relative decrease in cell number after 12 days, respectively in AO2V4 cells. GJC and GJR cell lines also responded significantly to the lowest concentration of IFN-beta tested and at 500 U/ml the relative cell number decreased 55%. The NN and NNR cells were the least responsive to IFN-beta with maximum growth inhibition of 30% at 500 U IFN-beta/ml. Following treatment with IFN-beta, AO2V4, GJC, GJR and normal astrocytes all expressed mRNA encoding the anti-viral protein, 2-5A synthetase demonstrating that IFN-beta bound to receptors on all four cell lines and activated signal transduction pathways required for induction of an anti-viral protein. A determination of the relative number of viable cells showed that none of these cells exhibited a significant decrease in cell viability. Since the antiproliferative response to IFN-beta was not primarily due to cell death, the effect of IFN-beta on cell cycle progression was evaluated by flow cytometry. All treated glioma cell lines showed a relative increase in proportion of cells in S phase. AO2V4 cells had a 50%-80% increase in the percentage of cells in S phase, whereas GJC, GJR and NNR had percentage increases of 20%-40%. IFN-beta treatment of normal astrocytes did not significantly alter their cell cycle profile. These data suggest that IFN-beta exerts its antiproliferative effect on glioma cells by arresting the ordered progression through S phase or decreasing entry into G2/M phase of the cell cycle.