Although selenoproteins are the predominant biologically functional form of Se synthesized by the Se metabolic system [31], we found that high doses of SS reduced GPx4 expression in an SS-dose-dependent manner, but did not affect the expression of other selenoproteins, such as selenoprotein P, TRXR1, and TRX1, in ovarian cancer cells in vitro and in vivo. This evidence concerns the gene TXNRD1 and ovarian cancer.