Effect of murine alpha-, beta-, and gamma-interferons in combination with alpha-difluoromethylornithine, an inhibitor of polyamine biosynthesis, on the tumor growth and metastasis of B16 melanoma and Lewis lung carcinoma in mice.

We have previously established that type I interferon (IFN), a mixture of alpha- and beta-IFN, augments the antitumor activity of alpha-difluoromethylornithine (DFMO), an inhibitor of polyamine biosynthesis, against B16 melanoma. The objective of the present investigation was to extend these earlier observations to metastatic Lewis lung carcinoma and to determine specifically which component(s) of type I IFN potentiates the antitumor activity of DFMO. Furthermore, we wanted to determine whether type II (gamma) IFN can also potentiate the antitumor activity of DFMO. Treatment of animals bearing Lewis lung carcinoma with DFMO, 2% in drinking water (3 g/kg/day), or IFN-alpha/beta (1000 units/mouse) given subcutaneously on alternate days for a total of ten doses alone resulted in 42 and 5% inhibition of tumor growth, respectively. A combination of DFMO and interferon brought about complete elimination of tumors in 12 of the 18 animals, and 94% inhibition of tumor growth in the remainder. DFMO or type I IFN administered alone caused 94 and 26% inhibition of metastasis, respectively. Combination treatment with these two agents resulted in complete elimination of visible metastases. Treatment of mice bearing B16 melanoma with DFMO resulted in 81% inhibition of tumor growth compared to controls. The administration of interferons alone resulted in tumor growth inhibition of 15, 3, 1, and 43% for type I, alpha-, beta-, and gamma-interferons, respectively. Treatment of animals with combination of DFMO and various interferons resulted in inhibition of 94, 93, 86, and 94% of B16 tumor growth for type I, alpha-, beta-, and gamma-interferons, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)