Reduced infiltration of T-regulatory cells in tumours from mice fed
daily with gamma-tocotrienol supplementation
Gamma-tocotrienol (γT3) is an analogue of vitamin E with beneficial
effects on the immune system, including immune-modulatory properties.
This study reports the immune-modulatory effects of daily
supplementation of γT3 on host T-helper (Th) and T-regulatory (Treg)
populations in a syngeneic mouse model of breast cancer. Female BALB/c
mice were fed with either γT3 or vehicle (soy oil) for 2-weeks via oral
gavage before they were inoculated with syngeneic 4T1 mouse mammary
cancer cells (4T1 cells). Supplementation continued until the mice were
sacrificed. Mice (n=6) were sacrificed at specified time-points for
various analysis (blood leucocyte, cytokine production, and
immunohistochemistry). Tumour volume was measured once every seven days.
Gene expression studies were carried out on tumour-specific
T-lymphocytes isolated from splenic cultures. Supplementation with γT3
increased CD4+ (p<0.05), CD8+ (p<0.05) T-cells and
natural killer cells (p<0.05) but suppressed Treg cells
(p<0.05) in peripheral blood when compared to animals fed with
the vehicle. Higher interferon-gamma (IFN) and lower transforming
growth factor-beta (TGF-) levels were noted in the T3 fed mice.
Immunohistochemistry findings revealed higher infiltration of CD4+
cells, increased expression of interleukin-12 receptor-beta-2
(IL-122R), interleukin-24 (IL-24) and reduced expression of cells that
express the forkhead box P3 (FoxP3) in tumours from the T3 fed animals.
Gene expression studies showed the downregulation of seven prominent
genes in splenic CD4+ T-cells isolated from γT3-fed mice.
Supplementation with γT3 from palm oil-induced T-cell dependent
cell-mediated immune responses and suppressed Treg cells in the tumour
microenvironment in a syngeneic mouse model of BC.