Implications of the inhibition of animal tumors by dietary zinc deficiency.

Because zinc is an essential nutrient for tissue growth, cellular division, protein synthesis, and DNA and RNA replication, it also ought to play a critical role in the growth of tumors. To test this thesis, a series of experiments were performed to test the effect of zinc deficiency on the lethality of a variety of solid and ascites tumors in mice and rats. Specifically, the following models were tested: Walker 256 carcinosarcomas, solid and ascites forms in rats; three mouse leukemias (L5178yf, L1210, and P388) in CDF, male mice; and Lewis lung carcinoma in C57BI/6 male mice. Rats receiving a zinc-deficient diet showed marked reduction of tumor growth, both of solid or ascites models, and this was accompanied by striking increase in survival. Survival of mice with transplanted leukemia was also significantly prolonged by zinc deficiency. In addition, growth of the Lewis lung carcinoma was inhibited, but the survival through increased, was probably limited by the adverse effects of zinc deficiency. The results suggest that tumor inhibition is a general effect of zinc deficiency, irrespective of cell type, cell growth rate, species, or site of growth. There are numerous potential applications of zinc metabolism to the diagnosis, therapy, and understanding of cancer.