Combined treatment of colon adenocarcinoma in rats with tumor necrosis factor and the interferon inducer ABPP.

It is well documented that the antitumor capacity of tumor necrosis factor (TNF) can be enhanced by interferons (IFNs), notably IFN-gamma. The aim of this study was to investigate the efficacy of a combined treatment with TNF and the IFN-inducer 2-amino-5-bromo-6-phenyl-4-pyrimidinone (ABPP) on a transplantable colon carcinoma (CC531) in rats. The tumor was implanted under the kidney capsule of syngeneic rats; the tumors were removed a week after implantation and growth was assessed by weighing. The animals were treated with 1 microgram of TNF, given i.v. on days 0, 2, and 4; and with 250 mg/kg of ABPP, administered i.p. on days 0 and 1. The results of two separate experiments indicated that both TNF and ABPP had a significant inhibitory effect on tumor growth. Combined, the two agents were found to act additively. In the dosage used, TNF toxicity was mild, transient, and not influenced by ABPP.