Dendrobium officinale polysaccharide promotes M1 polarization of TAMs to inhibit tumor growth by targeting TLR2

Promoting M1 polarization of tumor-associated macrophages (TAMs) is an effective pathway for malignant tumor therapy. In this study, we aimed to demonstrate whether homogeneous Dendrobium officinale polysaccharide (DOP) could promote M1 polarization of TAMs to inhibit tumor growth, and how it promoted. Results exhibited that DOP could inhibit the tumor growth and promote the M1 polarization of TAMs in tumor-bearing mice. Macrophage depletion and replenishment experiment clearly proved that the inhibitory effect of DOP on tumor growth is dependent on promoting M1 polarization of TAMs. Moreover, we found that DOP could reach tumor microenvironment (TME) and directly bind to TAMs to promote its M1 polarization via targeting toll-like receptor 2 (TLR2) after oral administration. These results clarified that DOP could remarkably inhibit the tumor growth of tumor-bearing mice via directly targeting the TLR2 of TAMs to promote its M1 polarization.