Oligo-fucoidan (Laminaria japonica Areschoug) remodeled the tumor microenvironment by decreasing the expression of immunosuppressive factors such as PD-L1 and IL-6, which stimulates T-cell immune surveillance and promotes the polarization of tumor-associated macrophages from the immunosuppressive M2 phenotype to the antitumor M1 phenotype. The gene discussed is CD274; the disease is neoplasm.