Astragaloside IV Exerts Anti-tumor Effect on Murine Colorectal Cancer by Re-educating Tumor-Associated Macrophage

Astragaloside IV (AS-IV) has shown anti-tumorigenic properties in certain cancers for its effect of boosting the body's immune system, but its role in colorectal cancer (CRC) remains unclear. In this study, we investigated the therapeutic effect of AS-IV in CRC and explored its underlying mechanism. CT26 colon cancer cells and mouse model by injection of CT26 cells subcutaneously were used as in vitro and in vivo model. M1 and M2 macrophage-associated markers, mRNA and protein expression levels were analyzed after AS-IV treatment. Inflammatory factors and cytokines in the tumors from mouse model were detected. Repolarization effect of AS-IV in vitro on bone-marrow-derived macrophages was also detected. In vitro, AS-IV inhibited the proliferation of CT26 cells and induced cell apoptosis dose-dependently, and significantly reduced M2 macrophages and increased M1 macrophages. In mouse model, it suppressed tumor growth and decreased the production of anti-inflammatory factors such as TGF-beta, IL-10 and VEGF-A, while increased the production of pro-inflammatory factors like IFN-gamma, IL-12 and TNF-alpha in tumor. Combination of AS-IV and checkpoint inhibitor aPD-1 exhibited synergistic antitumor effect by inhibiting tumor growth and increasing T cell infiltration. AS-IV could induce M2 macrophages polarization to the M1 phenotype. Its combination with immune checkpoint inhibitors could be expected to become a potential new strategy for the treatment of CRC.