Abstract: A method of treating metastatic cancer, comprising the steps of (a) treating a metastatic cancer patient with an isolated therapeutic Cystatin C peptide, and (b) observing a reduction in tumor burden is disclosed.

Abstract: A method is provided for inhibiting and substantially decreasing the motility of cells, and especially melanoma cells. In the invention, a cell is contacted with a motility-inhibiting amount of a metal ion selected from the group consisting of cobalt ion, the lanthanide metal ions, and mixtures thereof; particularly preferred metal ions are the Co2+ and Gd3+ ions. Metal ion sources may be administered in the form of soluble metal halide salts to in vitro to cells dispersed in an aqueous saline medium, or by administering an aqueous dispersion thereof to an in vivo mammalian subject at or adjacent a tumor site.