Quantitation of in vivo potentiation resulting from combined interferon therapy: antitumor effect against B-16 melanoma in mice

In this study, murine interferons (IFNs) were employed separately and in combination at subeffective and effective antitumor concentrations in a mouse B-16 melanoma system. Murine IFN-gamma (MuIFN-gamma) was demonstrated to be approximately 20 times more potent than MuIFN-alpha and MuIFN-beta in this system. Potentiation was observed with combinations of both subeffective and effective concentrations of MuIFN-gamma with MuIFN-alpha or MuIFN-beta. The level of potentiation was observed to increase from undetectable to two-fold to fourfold with three increasing IFN concentrations. Thirty percent of the mice treated for 14 days with 332 U/day MuIFN-gamma plus 7,500 U/day MuIFN-alpha survived apparently tumor-free for 100 days. Forty percent of the mice treated for 14 days with 332 U/day MuIFN-gamma plus 7,500 U/day MuIFN-beta survived apparently tumor-free for 100 days. All control mice died by day 41. The results are consistent with the suggestion that combination IFN therapy may have some use in the control of at least some tumors in humans.