ANTITUMOR EFFECT OF HUMAN RECOMBINANT INTERFERON-β AGAINST HUMAN MELANOMAS TRANSPLANTED INTO NUDE MICE

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The antitumor activity of recombinant human interferon-β (ReIFN-β) against 2 human melanomas, Mela3 and SK-MEL-26 cells, transplanted into nude mice was examined, comparing with that of natural interferon-β (IFN-β). The growth of Mela3 and SK-MEL-26 cells was inhibited significantly by the daily intravenous injection of 10⁸ units(U)/kg of ReIFN-β for 10 d starting from day 0. The effect of ReIFN-β decreased when its administration was started from the established stage of tumor development. Intravenous injection of 10⁷ U/kg of ReIFN-β or IFN-β did not significantly inhibit the growth of Mela3 cells. Mela3 cells, prepared from Mela3-bearing mice which had been injected 10⁸ U/kg of ReIFN-β intravenously for 10 d, showed the slight resistance to ReIFN-β in vitro. Intratumoral injection of 10⁷ U/kg of ReIFN-β in the established stage of tumor development inhibited the growth of Mela3 and SK-MEL-26 cells significantly. This effect of ReIFN-β was almost equivalent to that of IFN-β. From the histologocal examination, these effects of intratumoral injection of ReIFN-β or IFN-β were suggested to be mediated by their direct anticellular activities, but not by immunological activities. These results indicate that the in vivo antitumor activity of ReIFN-β was not essentially affected by the deficiency of carbohydrate.