Compositions and methods for decreasing the viability of cells, particularly aberrant non-healthy cells, and most particularly cancer cells, are disclosed. The primary agent that causes cell death is a toxic metal atom or ion. Embodiments of the invention provide compositions and methods to ensure that the toxic metal is directed to the desired cell or tissue. In one embodiment, the metal is bound to a sulfur-rich peptide or protein carrier containing a targeting moiety. Such metal-protein complex is targeted to the selected cells or tissues to enrich the cell or tissue site with the metal-containing peptide or protein molecules followed by administering a dithiocarbonyl which carries the metal from the protein inside the cells to induce cell death.