Organoselenium compounds in cancer chemoprevention.

Selenium is an important trace element involved in different physiological functions of human body. Knowledge of selenium in biology of cancer has increased at rapid rate especially during last two decades. Basic research and clinical studies involving animal models and more recently studies in human strongly support the protective role of selenium against various types of cancer. Selenium's role as an essential nutrient is as a result of its unique chemistry enabled by the presence of selenium in selenoproteins. Epidemiological findings have linked inadequate status of selenium to increased risk of cancer. The protective action of selenium is a combination of various mechanisms. Amongst all the diverse mechanism that have been proposed some important ones are (a) Protective role of selenoproteins/selenoenzymes (b) induction of apoptosis (c) immune system effects (d) detoxification of antagonistic metals (e) inactivation of nuclear transcription factor (f) regulation of lipoxygenases (g) effect on advanced cancer condition (h) reduction of oxidative stress (i) induction of Phase II enzymes (j) androgen receptor down regulation (k) inhibition of DNA adduct formation (l) cell cycle arrest. The purpose of this review is to focus the recent development in the field of cancer prevention utilizing selenium. The metabolism of selenium compounds , carcinogenesis studies, epidemiological data, and various proposed chemopreventive mechanisms of selenium compounds along with results of human intervention trials have been discussed.