Combination Cytokine Immunotherapy with Tumor Necrosis Factor α, Interleukin 2, and α-Interferon and Its Synergistic Antitumor Effects in Mice

The antitumor activity of combination therapy with recombinant human tumor necrosis factor a (rhTNF-a), recombinant human interleukin 2 (rhIL-2), and recombinant hybrid a-interferon A/D (rhIFN-a A/D) was assessed against established weakly immunogenic (MCA-106) and non-immunogenic (MCA-102) sarcomas at both s.c. and visceral (hepatic) sites. C57BL/6 mice were treated with a single i.v. dose of rhTNF-a followed by rhIL-2 (75,000 units) and rhIFN-a A/D (75,000 units) i.p. twice daily for 5 consecutive days. Substantial improvements were observed when the combination of rhTNF-a, rhIL-2, and rhIFN-a A/D was administered, as measured by regression of tumor, prolongation of survival, and improved cure rates, compared with any combination of two cytokines or any cytokine alone against the MCA-106 sarcoma. These findings were consistent in both the s.c. and single hepatic tumor models. For example, treatment of the MCA-106 s.c. tumor bearers with the triple cytokine combination resulted in cures of 16 of 18,17 of 18, and 12 of 18 mice receiving rhTNF-a dosages of 2, 4, and 6 Mg, respectively, compared with 2 of 18, 7 of 18, and 9 of 18 at 2,4, and 6 jig of rhTNF-a plus rhIL-2 without rhIFN-a A/D. Established 10-day single liver tumor weights when treated with the triple combination therapy were 54 and 25 mg in treatment groups receiving 2 and 4 μ of rhTNF-a, compared with 376 and 302 mg with the same amounts of rhTNF-a alone (P < 0.004). Mice bearing hepatic sarcomas treated with triple cytokine combination therapy had cure rates of 50% and 67% at rhTNF-a doses of 2 and 4 μg, compared with no survivors with rhTNF-a alone. No improved antitumor effects resulted from therapy with any cytokine alone or in combination against the nonimmunogenic MCA-102 sarcoma. Possible in vivo mechanisms by which these three cytokines synergize are discussed.