[Antineoplastic effect of beta-IFN and gamma-IFN on malignant gliomas]

We have compared the anti-tumor effects of beta- and gamma-interferons (IFN) against human glioma cells using in vitro model, flow cytometry and xenograft in nude mouse. Contrary to gamma-IFN which had a negligible effect on the growth of glioma cells, beta-IFN showed a dose dependent growth-inhibitory effect on glioma cells in vitro. Our flow cytometry studies revealed that proportion of DNA contents which represent the S and/or G2M phase of cell cycle was markedly increased in cells treated with beta-IFN. However, in cells treated with gamma-IFN, no perturbations in cell cycle distribution were observed. Regarding the anti-tumor effect examined using xenograft of human glioma cells in nude mouse, the tumor reduction rate which was calculated from the ratio of tumor volume between treated (T) and control (C) groups and expressed as T/C value, was 0.44 in animals treated with beta-IFN. However, T/C value in animals treated with gamma-IFN was 0.80 which was derived from the weaker anti-tumor effect of gamma-IFN as compared with that of beta-IFN. Beta-IFN was found to cause a partial suppression of the growth of glioma strain used in this study which confirms our previous report that beta-IFN is effective in reducing tumor size in 2 of 6 glioma strains tested. On the other hand the anti-tumor effect of gamma-IFN, at least in terms of direct effect, against glioma cells used in this study was minimum. However, the mechanism of gamma-IFN's anti-tumor effect may exert mainly through the potentiation of immuno-defence mechanism and the further studies on its pharmacodynamics will be necessary to evaluate the anti-tumor effect of gamma-IFN.