CSF1 and cancer: These cells are enriched with factors like periostin (OSF-2, an osteoblast-specific factor), TGF-β, and colony-stimulating factor 1.438 These factors drive the polarization of macrophages towards an immunosuppressive M2 or TAM phenotype.439 TAM-secreted molecules like WNT, TGF-β, and VEGF promote cancer stemness, create an immunosuppressive TME, facilitate EMT, and support cancer metastasis.440 Additionally, TAMs enhance PD-L1 expression on CTCs and PD-1 on T cells, thus dampening T-cell-mediated cytotoxicity.441