PROS1 and central nervous system cancer: In glioblastoma, flavonoids also target other pathways, including activation of cell surface death receptors (24), such as kaempferol, which enhances TRAIL-mediated apoptosis through the extrinsic and intrinsic apoptotic pathways (25), and quercetin, which sensitizes glioma cells to death receptor-mediated apoptosis by suppressing the inhibitor of the apoptosis protein surviving (25).