This study investigated the effect of recombinant human
tumor necrosis factor (rhTNF) on
hydroxyl radical production by established cell lines in vitro, and its implication in the killing of
tumor cells by rhTNF. During incubation of TNF sensitive mouse tumorigenic fibroblast L-M cells (2 X 10(7) cells) in the presence of rhTNF (100 U),
hydroxyl radical production as detected by the evolution of methane gas from
dimethyl sulfoxide increased gradually, at 18 h reaching 1.8 times that in the absence of rhTNF. This increase was dependent on the concentration of rhTNF and was effectively prevented by the simultaneous addition of anti-rhTNF
monoclonal antibody III 2F3, which inhibited both the binding of rhTNF to its receptor and the cytotoxic activity of rhTNF. The addition of
iron chelator 2,2'-bipyridine, which inhibits
iron-catalized Fenton reaction and so inhibits
hydroxyl radical generation, suppressed both the increase of
hydroxyl radical production and the cytotoxicity induced by rhTNF. A similar increase in
hydroxyl radical production in the presence of rhTNF was also detected with TNF-sensitive human
myosarcoma-derived KYM cells, but no such increase was detected with TNF insensitive human embryonic lung fibroblast HEL cells. The results show that rhTNF induces increased
hydroxyl radical production in TNF-sensitive cells, and suggest that this plays an important role in the mechanism of
tumor cell killing by rhTNF.