Metals and metal compounds in carcinogenesis.

Several metals and metal containing compounds are potent mutagens and carcinogens. The most often blamed are chromium, arsenic, nickel, vanadium, iron, copper and manganese. Although each of them has its own mechanism of action, it is believed that most of their mechanisms of action involve reactive oxygen species (ROS). Furthermore, nickel modulates gene expression by induction of DNA methylation and/or suppression of histone acetylation. Arsenic activity on cell metabolism is multiple; it seems that cell transformation is induced by long-term exposure to a low level of arsenic. The paradox of arsenic is that it has also a valuable therapeutic efficacy in cancer treatment. Manganese is known to cause DNA damage, although it does not represent a significant carcinogenic risk. Magnesium deficiency and iron excess are not exactly carcinogenetic, but certain concentrations of these metal ions are needed to prevent cancer.