c-Myc is expressed in human TAMs and regulates their phenotype. (A) c-Myc expression in human macrophages cultured or not in the presence of 20 ng/mL of IL-4 (M2 and M0, respectively) or culture medium conditioned by the human tumoral cell lines PANC-1 (pancreas tumor), SW480 (colon tumor), and MDAMB231 (breast tumor). Results are shown as means ± SD of n = 6 independent experiments. (B-C) Expression levels of ALOX15, MRC1, HIF1α, MMP9, TGFβ, and VEGF by single Q-PCR in human macrophages exposed for 24 hours to PANC-1–conditioned medium (B-C closed bars), in the presence of the c-MYC inhibitor 10058-F4 (60μM) (B open bars) or after suppression of c-MYC expression by macrophage transduction with a c-MYC/shRNA (C open bars). Results are the the -fold induction compared with untreated macrophages and represent the means ± SD of n = 4 independent experiments. (D-E) Double immunohistochemical analysis for CD68 (alkaline phosphatase staining: red color) and c-MYC (peroxidase staining: brown color) in specimens of colon cancer (D) and normal colon (E). Hematoxylin counterstaining. Magnification is 20×. In panel D, c-MYC expression is found in neoplastic cells (nuclear pattern, **) and in CD68⁺ macrophages of the lamina propria (double immunostaining: red and brown). A few c-MYC⁻/CD68⁺ macrophages are found (*). **Neoplastic glands; arrows, c-MYC⁺/CD68⁺ macrophages; *c-MYC⁻/CD68⁺ macrophages. In panel E, CD68⁺ macrophages, localized in the lamina propria of normal colon mucosa show no c-MYC immunostaining. **Normal colon glands; arrows, CD68⁺ macrophages. In both panels, inserts show high-magnification fields (100×) of c-MYC/CD68 immunostaining.