Synergistic action of human recombinant tumor necrosis factor with endotoxins or nontoxic poly A:U against solid Meth A tumors in mice

Abstract

Antitumor effects of i.v. injected human recombinant tumor necrosis factor (rTNF) against solid Meth A tumors in mice appeared to be critically dependent on the dose and were limited by its toxicity. Extensive necrosis and complete cures were only induced by doses having untoward effects, such as diarrhea, hypothermia, ruffled fur, and lethargy. Murine tumor necrosis serum (TNS, 0.5 ml) had about the same antitumor potential and induced all side effects except diarrhea. More extensive necrosis and approximate doubling of the incidence of complete regression in the absence of gross side effects were observed upon administration of a low dose of rTNF combined with detoxified endotoxin, nontoxic poly A:U, or submicrogram doses of toxic endotoxin. The separate constituents had little antitumor effects, if any at all. Increasing the dose of toxic endotoxin resulted in a further potentiation of necrosis, overt toxicity, but no cures. Muramyl dipeptide and interferon alpha/beta did not potentiate effects of rTNF. In vitro growth of Meth A cells was not inhibited by toxic endotoxin, rTNF or the combination, although TNS was highly inhibitory. Data show that therapeutic effects of rTNF and its synergy with endotoxin are not due to direct effects on the tumor cells and that the extent of prompt in vivo tumor necrosis does not predict the course of tumor growth. Therapeutic effects of both TNS and toxic endotoxin probably involve a synergy between low levels of TNF and other factors/effects induced by endotoxin. Detoxified endotoxin and poly A:U probably induce the latter effects and little or no TNF, so explaining the absence of side effects, their weak antitumor potential, and their powerful synergistic action with rTNF. A role for interferon alpha/beta as an induced synergistic factor is not likely. Muramyl dipeptide and TNF might share properties needed for synergy with endotoxins.

Effect of tumour necrosis factor and lipid A on functional and structural vascular volume in solid murine tumours

“…with one of two doses of TNF or lipid A or with a combination for macroscopic determination of hyperaemia and necrosis and assessment of FV and SV. Macroscopic effects of TNF and lipid A on the tumours were very consistent with those of previous studies Bloksma & Hofhuis, 1987;Van de Wiel et al, 1989). A dose of 3 x I04 U TNF caused marked red discolouration of the tumours at 4 h, and dark-stained necrosis of the central tumour portion at 24 h ( Table I).…”

“…. -.. -lipid A on FV supports the idea that early effects on FV are not crucial for tumour destruction, because all treatments reduced the FV to about the same degree at 4 h (Figure 4), while induction of tumour necrosis by the agents appeared to be dose-dependent (Table I; Bloksma & Hofhuis, 1987;Van de Wiel et al, 1989). At 24 h, however, blood flow had completely resumed in tumours of mice treated with the lower doses, but not at all or only partially after treatment with the high dose of TNF and lipid A, respectively.…”

“…Route-and time-dependence of the vascular effects of TNF A dose of 3 x IO' U TNF, which caused a reproducible high incidence of cures in previous experiments (Bloksma & Hofhuis, 1987;Van de Wiel et al, 1989), was injected i.v. or i.l.…”

“…Tumour necrosis factor (TNF), predominantly produced by mononuclear phagocytes upon injection of endotoxin, is assumed to be a pivotal mediator of this effect (Carswell et al, 1975), but an involvement of other endotoxin-induced factors is indicated by the synergic anti-tumour activity of endotoxin and TNF (Bloksma & Hofhuis, 1987;Chun & Hofmann, 1987). The synergy also indicates that the agents have a different mode of action.…”

“…Only TNF was found to display harmful effects to several neoplastic cell lines (Fransen et al, 1986;Nakano et al, 1986). Observa-tions, however, that TNF can induce extensive necrosis of tumours that lack sensitivity to TNF in vitro (Creasey et al, 1986;Asher et al, 1987;Bloksma & Hofhuis, 1987) suggest that, at least in these instances, the tumour cells are killed by an indirect mechanism. Ample data have indicated that the tumour vasculature is a primary target of the action of TNF and endotoxin (Gratia & Linz, 1931;Shear & Perrault, 1943;Kawai et al, 1987).…”