Reactions of 3-ethoxy-2-oxobutyraldehyde bis(N4-dimethylthiosemicarbazonato) cadmium with tumor cells.

The cytotoxic properties of a bis(thiosemicarbazonato) cadmium complex are studied. Preincubation of Ehrlich cells with the complex prevents growth of the ascites tumor in mice. Although the complex inhibits tumor growth without undue initial toxocity, longer-term side effects limit the use of the compound. The complex inhibits incorporation of 3H-thymidine into DNA and the respiration of tumor cells. It is shown in the principal correlation that the complex is more inhibitory of the above biochemical processes than cadmium ion at equal cellular concentrations of the metal. In addition the cellular reactions of the cadmium, zinc, and copper bis(thiosemicarbazonato) complexes are compared. It is shown that subtle chemical differences in their chelate structures appear to be responsible for their marked differences in cellular reactivity.