Fucoidan from Durvillaea Antarctica enhances the anti-cancer effect of anti-PD-L1 antibody by activating dendritic cells and T cells

Immune checkpoint inhibitors are showing groundbreaking results in tumor immunotherapy. However, there are cases where treatment efficiency is insufficient due to limitations in immune activity, and various trials to overcome this are being studied. In this study, we investigated the immune activation ability of fucoidan extracted from Durvillaea antarctica (FDA) and whether it can enhance the anti-cancer effects of immune checkpoint inhibitors. FDA treatment resulted in an elevation of co-stimulator and major histocompatibility complex molecule expression, as well as the production of pro-inflammatory cytokines in bone marrow-derived and splenic dendritic cells (DCs). Administration of 50 mg/kg FDA increased the number of splenic CD8 T cells by >1.4-fold compared to PBS administration. Additionally, 50 mg/kg FDA increased the production of IFN-γ in CD4 and CD8 T cells by 4.3-fold and 7.2-fold, respectively, compared to the PBS control. FDA promoted immune cell activation was TLR4 dependent. Furthermore, anti-PD-L1 antibody administration inhibited CT-26 tumor growth by approximately 3-fold compared to the PBS control group, whereas combined treatment with FDA and anti-PD-L1 antibody showed an 8.4-fold tumor growth inhibition effect compared to the PBS control group. Therefore, FDA may be used to enhance the anti-cancer effects of immune checkpoint inhibitors.