Our objectives were to determine if porcine serum could be enriched with selenium (Se) by feeding pigs with high concentrations of dietary Se and if the Se-biofortified serum inhibited proliferation of 3 types of human cancer cells. In Expt. 1, growing pigs (8 wk old, n = 3) were fed 0.02 or 3.0 mg Se/kg (as sodium selenite) for 16 wk and produced serum with 0.5 and 5.4 μmol/L Se, respectively. In Expt. 2, growing pigs (5 wk old, n = 6) were fed 0.3 or 1.0 mg Se/kg (as Se-enriched yeast) for 6 wk and produced serum with 2.6 and 6.2 μmol/L Se, respectively. After the Se-biofortified porcine sera were added at 16% in RPMI 1640 to treat NCI-H446, DU145, and HTC116 cells for 144 h, they decreased (P < 0.05) the viability of the 3 types of human cancer cells by promoting apoptosis, compared with their controls. This effect was replicated only by adding the appropriate amount of methylseleninic acid to the control serum and was mediated by a downregulation of 8 cell cycle arrest genes and an upregulation of 7 apoptotic genes. Along with 6 previously reported selenoprotein genes, selenoprotein T (Selt), selenoprotein M (Selm), selenoprotein H (Selh), selenoprotein K (Selk), and selenoprotein N (Sepn1) were revealed to be strongly associated with the cell death-related signaling induced by the Se-enriched porcine serum. In conclusion, porcine serum could be biofortified with Se to effectively inhibit the proliferation of 3 types of human cancer cells and the action synchronized with a matrix of coordinated functional expression of multiple selenoprotein genes. J. Nutr. 143: 1115-1122, 2013.