Tumor necrosis factor (TNF)-induced inflammation prevents its broad application as an antitumor agent. We here report that addition of ZnSO(4) to the drinking water of mice induces expression of heat shock protein 70 (HSP70) in several organs, notably the gastrointestinal track. Zinc conferred dose-responsive protection against TNF-induced hypothermia, systemic induction of interleukin-6 and NO(x), as well as against TNF-induced bowel cell death and death of the organism. The protective effect of zinc was completely absent in mice deficient in the major HSP70-inducible gene, hsp70.1, whereas transgenic mice constitutively expressing the human HSP70.A gene, under control of a beta-actin promoter, was also protected against TNF, indicating that an increase in HSP70 is necessary and sufficient to confer protection. The therapeutic potential of the protection induced by ZnSO(4) was clearly shown in a TNF/IFNgamma-based antitumor therapy using three different tumor models. In hsp70.1 wild-type mice, but not in hsp70.1-deficient mice, zinc very significantly protected against lethality but left the antitumor effect intact. We conclude that zinc protects against TNF in a HSP70-dependent way and that protection by zinc could be helpful in developing a safer anticancer therapy with TNF/IFNgamma.