Effects of dietary zinc on melanoma growth and experimental metastasis

These studies were designed to determine the effects of zinc on in vitro melanoma cell growth and in vivo metastasis. Cultured P51 mouse melanoma cells were larger, had longer doubling times and a decreased rate of tritiated-thymidine uptake when grown in zinc depleted compared to standard medium. Experimental metastasis was evaluated using intravenously injected, radiolabelled melanoma cells. Cell distribution and survival were determined 1, 3 and 21 days post-injection in C57BL/6 mice fed low zinc (0.5 and 4.0 mg Zn/kg) or stock diets. Altered organ distribution and survival of melanoma cells were observed in the zinc depleted dietary groups compared to the stock diet group. After 21 days of tumor growth, lungs of mice fed diets low in zinc contained up to 50% fewer labelled tumor cells than those of mice fed the stock diet. Livers of mice in the 0.5 mg Zn/kg group contained a greater percentage of tumor cells 21 days post-injection than those of mice fed the stock diet. Thus, dietary zinc can influence experimental tumor metastasis through modification in organ distribution of tumor cells and their subsequent survival.