Essential elements, mainly selenium (and zinc), are involved in the protection against oxidative stress, as well as in oxidation-induced programmed cell death, which make them a distinct antitumorogenic agent. Selenium (Se) shows a multifunctional action that leads to preventing cancer development. Mechanisms of anticarcinogenetic Se activity seem to depend on selenium dosage, chemical form of selenium, and its metabolism. This "double-edge sword" acts as a reactive species scavenger due to Se-dependent glutathione peroxidases, thioredoxin reductases, and other selenoproteins. Epidemiological studies have show that low Se levels are associated with a 2-fold to 6-fold cancer risk in the lowest tertile or quintile (depending on the study). Modulation of xenobiotic metabolizing enzymes by selenium compounds also can inhibit reactive oxygen species generation. However, chemopreventive activity of selenium induces cell cycle arrest, which can lead to apoptosis. The association between zinc and antioxidative processes has not as yet been explicitly defined. Researchers suggest that zinc has the capacity to act in synergism with vitamin E to protect cellular membranes against oxidative stress. Zinc has been shown to compete for iron binding sites, providing protection aginst iron-mediated DNA damage.
Comments on Toxicology
Volume 9, 2003 - Issue 1