Selenium in colorectal and differentiated thyroid cancer.

The current review aims to provide a brief overview of developments in the research field of selenium and cancer. The focus is on two tissues that show a rising incidence of cancer cases each year, namely the colon and the thyroid. Effects of adequate selenium concentrations on tumor development are most probably mediated by selenoproteins. However, the role of selenoproteins changes during the carcinogenic process as well as in a tissue-specific manner. During the initiation phase, selenoproteins protect cells from oxidative DNA damage and thus appear to inhibit tumor development, whereas, in already existing tumor cells, selenoproteins might, on the contrary, support their growth and thus reduce the survival probability of patients.