Figure 3.

Recruitment and M2 polarization of macrophages in bladder cancer. Macrophages are recruited to the tumor by chemokines such as CCL2, CCL5, and CSF-1 which are often released by the tumor itself. In the tumor, they are polarized toward an M2 phenotype by the action of mediators including TGF-β, CCL2, IL-10, and BMP-4. This phenotype is characterized by CD163 expression, suppression of T cell responses, tissue remodeling and promotion of angiogenesis. This is mediated amongst other things by the production of vascular endothelial growth factor (VEGF) and IL-10, and the high expression of inhibitory checkpoint molecules such as PD-L1.