Copper and metallothioneins in cancer cells.

Metallothioneins (Mts) are intracellular proteins whose biological function is zinc and copper regulation as well as detoxification of toxic metals. Another function of these proteins is sweeping away free radicals. MT synthesis induction is stimulated by such factors as metallic ions, free radicals, cytokines, lymphokines and stress. An increased intracellular metallothionein expression was found in many human and animal neoplasms. Copper functions as cofactor in various redox enzymes. At the same time, copper is very toxic to both eukaryotic and prokaryotic cells. Copper ions can bind to proteins and nucleic acids and cause the oxidation of lipids and proteins. The formation of deleterious free radicals is also enhanced by copper ions. For cell viability, regulation of intracellular copper activity is thus crucially important and mechanisms must exist for the homeostasis of copper. An elevated copper level is noted in many types of neoplastic tissue.