Figure 2

M2-polarized macrophages enhance lung metastasis of 4T1 cells in the 4T1 orthotopic mouse tumor model. 4T1 cells and/or M2-polarized macrophages (M2-Mϕs) were injected into the mammary fat pads of female Balb/C mice. After 3 weeks, the mice were killed and the lungs were removed and fixed in Bouin's solution. (A) Photographs of lung metastasis. (B), (C) Quantitative analysis of lung tumor nodules. Each bar represents the mean ± standard error of the mean (n = 8). *Significantly different from the group injected with 4T1 cells alone, P < 0.05. (D) Tumor sections were stained with their relevant antibodies as described in the Materials and methods section. Photographs of immunohistochemical or immunofluorescent staining, which are representative of six different animals, are shown. HIF-1α, hypoxia-inducible factor-1 alpha; VEGF, vascular endothelial growth factor; LYVE-1, lymphatic vessel endothelial hyaluronan receptor-1.