Immune-checkpoint blockade has transformed oncology, but primary and acquired resistance continue
to limit durable benefit. Programmed death-ligand 1 (PD-L1) contributes to immune escape through
canonical T-cell suppression, tumor-intrinsic signaling, post-translational regulation, and extracellular
trafficking. Tocotrienols—unsaturated vitamin E isoforms present in palm oil—are emerging as
candidate modulators of this interface. This qualitative literature review synthesizes evidence published
predominantly during 2020–2026 on β-, γ-, and δ-tocotrienol in relation to PD-L1 biology, tumor
immune escape, treatment sensitization, and checkpoint immunotherapy. β-Tocotrienol suppresses
PD-L1-associated signaling partly through JAK2/STAT3 modulation, whereas δ-tocotrienol disrupts
PD-L1 N-glycosylation through the TCF4–STT3A/STT3B axis and can modify treatment resistance.
Most notably, recent preclinical evidence indicates that γ-tocotrienol can enhance anti-PD-1 activity
in colorectal cancer by increasing CD8+ T-cell function, reducing regulatory T-cell abundance,
remodeling macrophages, and increasing MHC-I-associated tumor visibility. However, no clinical trial
has established tocotrienol-mediated improvement of checkpoint-inhibitor efficacy, and existing phase
II cancer studies of δ-tocotrienol have not demonstrated clear antitumor benefit. We therefore propose
a three-level translational framework—checkpoint modulation, tumor/immune sensitization, and
genuine immunotherapy enhancement—and identify pharmacokinetic, biomarker, and model-validation
requirements for clinical translation.
10.33425/2693-1516.1083
Published: 25 Oct, 2026