Endogenous production of tumor necrosis factor in normal mice and human cancer patients by interferons and other cytokines combined with biological response modifiers of bacterial origin.

The priming effect of endogenous biological response modifiers (BRMs), interferons (IFNs), and interleukin-2 (IL2), and the triggering effect of BRMs of bacterial origin, OK-432 and Corynebacterium parvum, on endogenous production of the tumor necrosis factor (TNF) were investigated in mice. TNF activity in serum was measured by in vitro cytotoxicity assay with L-929 cells as a target. The i.v. injection of OK-432 (3KE per mouse) triggered TNF maximally (mean value: 30 U/ml) after 2 h, with a similar time course to that of triggering by lipopolysaccharide. The priming activities of IFNs and IL2 were examined in the system of TNF-triggering by OK-432. The i.v. injection of recombinant IFN-gamma (rIFN-gamma, 10(4) U per mouse) increased TNF production to 790 U/ml; this priming effect was observed just after its injection, was maximal after 2 to 6 h, and disappeared after 24 h. Other types of interferon, rIFN-alpha A/D(Bgl) (2 X 10(5) U per mouse), rIFN-beta (10(6) U per mouse), and natural IFN-alpha/beta (10(6) U per mouse) showed maximal priming activity 6 h after their injection (200 to 800 U/ml) but no effect just after their injection. Recombinant IL2 (10(6) U per mouse) had priming activity that showed a similar time course to that of interferons other than IFN-gamma (a maximal TNF production: 100 U/ml). The i.v. injection of C. parvum, like OK-432, triggered TNF production at doses of 0.06 and 0.3 mg per mouse 2 h after its injection and the triggered TNF activity was enhanced by rIFN-gamma. These findings suggest that combinations of the above endogenous BRMs as priming agents and OK-432 or C. parvum as a triggering agent could induce endogenous production of TNF even in human cancer patients. In fact, combined administration of rIFN-gamma and OK-432 produced TNF in human cancer patients. The advantage of this method for treatment of human cancer patients is discussed.