The hypothesis that in
tumor-bearing animals an increase of host hepatic
zinc metallothionein (Zn-MT) causes a restriction of
zinc in the
tumor tissue was studied. Three types of
tumors were induced in laboratory mice by cell transplant.
Tumor growth appears to be inhibited under
zinc-deficient conditions, even in cases where
zinc deficiency was started after
tumor cell transplant. The survival times of
tumor-bearing mice were prolonged by administration of
cadmium chloride, which induces the synthesis of a combined
zinc-
cadmium metallothionein derivative in the host liver, but not in the
tumor tissue, leading to an increase of hepatic
zinc in the treated animals. The uptake of 65Zn by the liver of Cd-treated,
tumor bearing mice was significantly higher than that of controls whereas uptake of 65Zn by
tumor cells was significantly higher in controls than in the treated animals. These results suggest that restriction of
zinc intake suppresses
tumor growth.