Journal of Neuro-Oncology 30: 213-223,1996. © 1996 Kluwer Academic Publishers. Printed in the Netherlands. Laboratory Investigation Interferon-J3 inhibits proliferation and progression through S phase of the cell cycle in five glioma cell lines Judith I. Garrison, 1Michael E. Berens, 2Joan Rankin Shapiro, 2 Sherri Treasurywala~and Georgia Floyd-Smith ~ 1 Department of Zoology, Arizona State University, Tempe, Arizona 85208-150I; 2 Neuro-Oncology Research Laboratory, Barrow Neurological Institute, St. Joseph's Hospital and Medical Center, Phoenix, A Z 85013-4496, USA Key words: 2-5A synthetase, astrocyte, cancer, cell cycle, cell death, flow cytometry, glioblastoma multiforme, glioma, interferon, recurrent tumor Summary The growth inhibitory effect of IFN-[3 was evaluated in 5 human glioma cell lines (AO2V4, GJC, G JR, NN and NNR) and in normal astrocyte cultures (SC and TM). All 5 glioma cell lines showed an anti-proliferative response to IFN-13 whereas normal glial cells were non-responsive. IFN-~3 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 significantlyto the lowest concentration of IFN-13 tested and at 500 U/ml the relative cell number decreased 55 %. The NN and NNR cells were the least responsive to IFN-[3 with maximum growth inhibition of 30% at 500 U IFN-[3/ml. Following treatment with IFN-~, AO2V4, GJC, G JR and normal astro- cytes all expressed mRNA encoding the anti-viral protein, 2-5A synthetase demonstrating that IFN-[3 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-[~ was not primar- ily due to cell death, the effect of IFN-[3 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-[3 treatment of normal astrocytes did not significantly alter their cell cycle profile. These data suggest that IFN-[3 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. Introduction Glioblastoma multiforme continues to be a lethal malignancy with a mean survival time of 58 weeks despite treatment which includes surgery, radio- therapy and chemotherapy [1]. These tumors exhib- it a high degree of regional and cellular heteroge- neity which is reflected in differential sensitivities of the tumor cell populations to specific chemother- apeutic drugs [2]. More recently, therapy with nat- ural substances, including the interferons (IFNs) has been explored and has shown some promise [1]. Clinical trials of IFN-[3, for example, have resulted in partial remission in 50% or more of patients test- ed [3, 4] suggesting that this cytokine could be in- corporated into a treatment regimen for malignant gliomas. Initial interest in the IFNs as anti-cancer agents