Abstract Text: Thiodigalactoside (TDG), a synthetic inhibitor of β-Galactoside Binding Protein (β-GBP), an immuno-modulatory protein, which regulates regulatory T cells (Tregs) which are responsible for tumor immuno-suppression. We observed the skewed immunological balance between Treg (CD4+CD25+FOXP3+) and Th17 (CD4+IL17A+) cells in peripheral circulation of oral squamous cell carcinoma (OSCC) patients by multicolor flowcytometry. The anti-tumour effects were studied by performing MTT, propidium iodide (PI) staining, annexin-V binding assay and ELISA respectively. The Tregs used in all co-culture assays were separated by MACS. An increased Th17/Tregs ratio was observed in oral cancer patients leading to immuno-suppressive tumor microenvironment. Treatment of oral cancer cells with β-GBP showed growth promoting effects i.e. significant increase in growth and angiogenesis of oral cancer cells. It also showed proliferative effect on Tregs. However, the treatment with its inhibitor TDG showed cytotoxic effects on both the Treg cell subsets and also oral cancer cells. TDG treatment resulted in Treg cell growth inhibition and also decreased frequency of IL10+ and IL35+ Treg cells indicating less immuno-suppressiveness. Subsequently, TDG treatment significantly (p < 0.001) inhibited the growth of OSCC cells with a concomitant induction of apoptosis, cell cycle arrest and anti-angiogenesis. It appears that TDG concurrently prevents many tumor promoting effects by Treg inhibition. Therefore, therapeutic targeting of β-GBP by TDG can overcome Treg mediated immunosuppression in oral cancer patients. Hence, TDG may be developed as chemopreventative/chemotherapeutic drug for treatment of patients with OSCC.
