Studies of the mechanisms of toxicity of the administration of recombinant tumor necrosis factor α in normal and tumor-bearing mice

Abstract

Tumor-bearing mice have a greater sensitivity to the acute lethal effects of the administration of high-dose recombinant human tumor necrosis factor α (rhTNF-α) compared to normal, non-tumor-bearing mice. We studied whether or not the presence of tumor per se was responsible for the enhanced rhTNF-α toxicity. Tumor-bearing mice underwent tumor excision or sham operation before the systemic administration of rhTNFα at staged times (0.5–24 h) following surgery. There was little survival difference between sham-operated tumor-bearing mice and tumor-bearing mice undergoing tumor excision (at 24 h, treatment with 12 µg rhTNF-α, survival:sham-operated tumor bearers = 0/12, excised tumor-bearers = 0/12;P² P² <0.001). Since the production of oxygen free-radical metabolites has been postulated to play a role in the acute toxicity of rhTNF-α, bismuth subnitrate was used to induce the enzyme metallothionein to act as a natural scavenger for these metabolites. Daily oral bismuth subnitrate treatments improved survival of mice with MCA-106 or MCA-102 sarcoma and of mice without tumors, with higher rhTNF-α doses (12–20 µg), without reducing the therapeutic effect of rhTNF-α against the weakly immunogenic MCA-106 sarcoma. These studies suggest methods for reducing the toxicity of rhTNF-α administration in clinical trials.