Several epidemiological studies suggest that Se status is inversely correlated with cancer incidence and mortality [20]–[23], but Se supplementation trials failed to show benefit, possibly due to the fact that the advantages of Se supplementation are dependent on several factors including baseline Se status, genetic background (e.g. the existence of polymorphisms in selenoprotein genes), type of cancer, as well as the metabolic conversion and dose of Se supplements [24]. Here, SELENOS is linked to cancer.