Growth-inhibitory activity of recombinant human interferon-beta against cultured human cells

The growth-inhibitory activity of recombinant human interferon-beta (ReIFN-beta) against cultured human cells was compared with that of natural human fibroblast interferon-beta (IFN-beta), and the influence of deficiency of carbohydrate on the anticellular activity was examined. The IC50 (concentration of drug required for 50% inhibition) of ReIFN-beta against 14 human cell lines was almost equivalent to that of IFN-beta, when the cells were cultured for 7 days and ReIFN-beta or IFN-beta was added on day 0 and exchanged every day from day 1 to day 6. The most sensitive cells (ICE less than 10 units/ml) were Daudi lymphoma cells and 3 melanoma cell lines, and the most insensitive cells (IC50 greater than 10(3) units/ml) were HeLa S3/IS cells (insensitive line) and CCRF-CEM leukemia cells. The other 8 cell lines were moderately sensitive to both interferons. As the intervals of exchange of ReIFN-beta or IFN-beta were extended, the growth-inhibitory activity of both interferons decreased. This phenomenon, which was more significant with ReIFN-beta than IFN-beta, was explicable in terms of the stability of both interferons incubated in the culture medium at 37 degrees. The species specificity of IFN-beta was not mediated by carbohydrate since the growth-inhibitory activity of ReIFN-beta against 2 mouse cell lines was almost equivalent to that of IFN-beta. These results indicate that the anticellular activity of ReIFN-beta was not essentially affected by deficiency of carbohydrate.