The effect of Zn2+ on mouse
melanoma growth in vitro and in vivo was studied. Under in vitro conditions the proliferation of a Cloudman mouse
melanoma cell line was inhibited by
zinc ions at 10(-4) M, as measured by 3H-thymidine incorporation and optical density of NaOH cell digests. However, in vivo it was not possible to suppress both B16 and
Cloudman S91 melanoma growth in mice by the administration of
zinc ions. There were no significant differences in
tumor growth after subcutaneous inoculation between mice constantly receiving 0.1%
zinc acetate or 0.05%
zinc sulphate in their
drinking water and control groups, nor was it possible to decrease the number of lung
metastases by
zinc treatment after intravenous inoculation of
tumor cells. The increased dietary supply of Zn failed to influence the survival time of mice in both
melanoma types studied. Preincubation in vitro of cell
suspensions in 10(-3) M
zinc acetate prior to injection inhibited
melanoma development in vivo. This implies that the in vivo
zinc levels did not reach the necessary cytotoxic concentration.