Potential Anti-proliferative and Immunomodulatory Effects of Marine Microalgal Exopolysaccharide on Various Human Cancer Cells and Lymphocytes in Vitro

Marine microalgal exopolysaccharides (EPSs) have drawn great attention due to their biotechnological potentials such as anti-viral, anti-oxidant, anti-lipidemic, anti-proliferative, and immunomodulatory activities, etc. In the present study, the EPS derived from microalgae Thraustochytriidae sp.-derived mutant GA was investigated for its anti-proliferation and immunomodulation. Anti-cancer efficacy of the microalgal EPS was examined for the alterations in cell proliferation and cell cycle-related gene expression that occur in three types of human cancer cell lines, BG-1 ovarian, MCF-7 breast, and SW-620 colon cancer cell lines, by its treatment. Alterations in immunoreactivity by the microalgal EPS were examined by measuring its influence on the growth of T and B lymphocytes and cytokine production of T cells. In cell viability assay, the microalgal EPS inhibited cancer cell growth at the lowest concentration of 10 −11 dilution and in a dose-responsive manner within the range of dilution of 10 −11 ~10 −3 . In addition, the protein expression of cell cycle progression genes such as cyclin D1 and E in these cancer cell lines was significantly reduced by the microalgal EPS in a dose- and a time-dependant manner. In cell proliferation assay using T and B cells, the microalgal EPS induced B cell proliferation even at the lowest dilution of 10 −11 , but not T cells. In cytokine assay, the microalgal EPS decreased the formation of IL-6 and INF-γ at 10 −3 dilution compared to the control and had no significant effects on TNF-α. Collectively, these findings suggest that the EPS derived from microalgae Thraustochytriidae sp. GA has an anti-proliferative activity against cancer cells and an immunomodulatory effect by having an influence on B cell proliferation and cytokine secretion of T cells.