δ-Tocotrienol

δ-Tocotrienol is a form of vitamin E that disrupts PD-L1 glycosylation by inhibiting the TCF4-STT3 pathway, leading to lower PD-L1 expression and reduced exosomal release. This reduction in PD-L1 impairs the PD-L1/PD-1 interaction, thereby reversing immune suppression. It also inhibits prostate cancer development by reducing cell proliferation, promoting apoptosis, and blocking angiogenesis in Ptenp−/− mice.