TGFB1 and neoplasm: Thus, we co-stained TGF-β1 with a murine macrophage marker, the protein F4/80 (Figure 3B), demonstrating that TGF-β1 and F4/80+ cells were predominantly localized in the peritumoral areas and, therefore, that macrophages might be an important source of TGF-β1 in the tumor microenvironment.