Positive interactions between human interferon and cyclophosphamide or adriamycin in a human tumor model system.

Human lymphoblastoid interferon strongly increased the anti-tumor activity of suboptimal doses of two commonly used anti-cancer drugs, cyclophosphamide and Adriamycin, on a human breast tumor xenograft growing in nude mice. A combination of human lymphoblastoid interferon with either of these agents caused regression and in some cases total disappearance of tumors at doses of drug and interferon that, used singly, were capable only of inhibiting tumor growth. The combined therapy also resulted in a greatly increased survival. Studies with interferon and cyclophosphamide indicated that the antitumor activity was greatest when the two agents were administered simultaneously rather than sequentially.