Abstract:
Immune system plays pivotal role against cancer progression. However, in the event of cancer development, tumour cells trigger immunosuppressive environment via the myeloid-derived suppressor cells and the T-regulatory (Treg) cells. The Treg T cells are a subset of CD4+ T lymphocytes, which have crucial roles in regulating immune homeostasis and promoting the establishment and maintenance of peripheral tolerance. Studies have reported palm oil as rich source of tocotrienol that able to exhibit anti-tumour and immunomodulatory properties in mouse breast cancer model. However, the most potent isomer of tocotrienol namely gamma-tocotrienol (γT3) modulating host immune system of mouse breast cancer model has not yet been elucidated. Hence, this study was targeted to investigate T-helper and T-regulatory cell population and mechanism involved upon supplementation of γT3. The in vivo study consists of treatment and prevention model. In treatment model, female BALB/c mice were induced with breast cancer and once a tumour was palpable, fed with either soy oil (vehicle) or gamma-tocotrienol (γT3) up to 35 days. In prevention model, female BALB/c mice were fed with either soy oil (vehicle) or gamma-tocotrienol (γT3) for two weeks. Then two groups were inoculated with tumour cells and remaining two groups were not inoculated with tumour cells. All the mice continued to receive the same supplementation until day 49. Every seven days six mice from each group were culled. The peripheral blood was used for flowcytometry analysis, organs collected for histology, tumour collected for immunohistochemistry, and spleen culture for CD4+ T-cell isolation and gene expression study. Although treatment model showed reduction in tumour volume and weight other immunological results were not promising. The prevention model results showed reduction in tumour volume and weight in γT3 fed mice. Interestingly, γT3 increased necrosis in tumour tissue and prevents metastasis in lung and liver of tissue sections. Flow cytometry analysis revealed T-helper cell population (CD4+, CD8+ and NK cell) were increased and T-regulatory cells were suppressed in γT3 treated mice. Increased level of IFN-γ and suppressed level of TGF-β cytokines were noted in γT3 mice. In addition, immunohistochemistry analysis showed strong expression of CD4+, moderate expression of IL-12Rβ2, IL-24 and weak expression of FoxP3 in the γT3 fed mice. Results from mouse T-helper array showed, γT3 regulated immune response pathway by expressing 10 genes namely IFN-γ, IL-2, IL-5, CCL5, CCL11, CCR4, RORA, RORC, IL-9 and FoxP3. Among this, IFN-γ, IL-2 and IL-17A were identified as robustly expressed genes by γT3. In conclusion, γT3 showed anti-tumour and immune modulatory activities by increasing T-helper population in immunocompetent mice via immune response pathway. Therefore, γT3 supplementation showed good prognosis in breast cancer induced mouse and can be considered as an immunotherapeutic agent for the treatment of breast cancer.
