SELENOF and cancer: It has been demonstrated that some polymorphic variants in genes encoding for selected selenoproteins, including GPX1 (glutathione peroxidase 1), GPX4 (glutathione peroxidase 4), SEPP1 (selenoprotein P), SELS (selenoprotein S), and SEP15 (15-kDa selenoprotein), have functional significance and may influence expression or activity of the protein either at the transcription, translation, or posttranslational level, thus explaining their association with the altered risk of cancer at several sites [17].