NF-κB pathways are involved in M1 polarization of RAW 264.7 macrophage by polyporus polysaccharide in the tumor microenvironment

Bladder cancer is one of the most malignant tumors closely associated with macrophages. Polyporus polysaccharide (PPS) has shown excellent efficacy in treating bladder cancer with minimal side effects. However, the molecular mechanisms underlying the effects of PPS in inhibiting bladder cancer remain unclear. In this study, we used macrophages cultured alone or with T24 human bladder cancer cell culture supernatant as study models. We found that PPS enhanced the activities of IFN-γ-stimulated RAW 264.7 macrophages, as shown by the release of inducible nitric oxide synthase (INOS), secretion of tumor necrosis factor (TNF)-α and interleukin (IL)-6, phagocytosis activity, as well as expression of M1 phenotype indicators, such as CD40, CD284 and CD86. PPS acted upstream in activation cascade of nuclear factor (NF)-κB signaling pathways by interfering with IκB phosphorylation. In addition, PPS regulated NF-κB (P65) signaling by interfering with Toll-like receptor (TLR)-4, INOS and cyclooxygenase (COX)-2. Our results indicate that PPS activates macrophages through TLR4/NF-κB signaling pathways.