Forms of selenium in cancer prevention

Selenium-containing compounds are known to play an important role in protection against several diseases, including cancer (Fairweather-Tait et al., 2011); however, the mechanisms that can account for cancer prevention remain undefined. Humans have 25 genes coding for selenoproteins by which selenium exerts its biological functions. Selenoproteins contain selenocysteine at their active sites (Papp et al., 2007) (see Chapter 3). Both inorganic and organic forms of selenium compounds can be metabolized in a way that they can supply the requisite selenium for synthesis of these selenoproteins (see Chapter 2). The form as well as optimal levels of selenium for maximal expression of individual selenoproteins and those required for maximal chemoprevention in preclinical animal models have been reported in the literature (El-Bayoumy, 2004; Weekley and Harris, 2013); at present, literature data strongly suggests that, in addition to supplying selenocysteine for synthesis of selenoproteins, different forms of selenium may act as chemopreventive agents through alternative mechanisms (Christensen, 2014).