Flow cytometric analysis of antineoplastic effects of interferon-α, β and γ labelled with fluorescein isothiocyanate on cultured brain tumors

Summary

Antineoplastic effects of interferons (IFNs) on brain tumors have often been reported in the literature, however, so far as we know, there are no reports of the study on the antineoplastic effect of IFNs (α, β, and γ) labelled with fluorescein isothiocyanate (FITC) using flow cytometry (FCM). Three established glioma cell lines and 11 cultured cells of brain tumor from surgical specimens were exposed to IFN-α, β, and γ at the concentrations of 10²–10⁵ IU/ml for 24 h, respectively. Using FCM, the viability of the cells was evaluated with fluorescein diacetate stain and the cell cycle was analyzed from the DNA-histogram with propidium iodide stain. Furthermore, FITC-labelled IFN-α, β and γ were also contacted with each cell to calculate respective positive cells. The viability decreased about 60% on day 1 and day 3, indicating the effect of IFN-α and β on U373MG cells and on some cultured glioma cells from surgical materials, whereas, IFN-γ had no effects. Antineoplastic effect of each IFN well correlated with FITC-positive rates, demonstrating S phase block in the cell cycle. IFN-γ had no antineoplastic effects, whereas IFN-α and β showed antineoplastic effects, which fact suggested that IFN-γ receptor be different from those of IFN-α and β. The method of FITC-labelling for IFNs with the aid of FCM has the advantages as follows: 1) Antineoplasticity of IFN can be simply evaluated with FCM; 2) It is easy to analyze the action mechanism of IFN; 3) Information on the receptor is obtainable; and 4) Sensitivity can be evaluated prior to administration of IFN, suggesting possibilities of clinical application of this method.