Fig 2

M2 macrophages promote cancer cell metastasis. a Confocal microscopy of immunostained macrophages. THP-1 monocytes were polarized into M1 or M2 macrophages. Macrophages were labeled with anti-HLA-DRα or anti-CD206. The nuclei were counterstained with DAPI. Scalebar, 20 μm. b Gene expression profiles of M1 and M2 macrophages. M1 and M2 macrophage gene expression levels were quantified using real-time PCR. The genes are shown on the horizontal axis. c, d, e Cancer cell migration characterized using Boyden chamber assays. Gastric cancer cells (MKN-45, AGS, MGC-803, and HGC-27), breast cancer cells (MDA-MB-231, MDA-MB-435, and MDA-MB-468), or melanoma cells (A375) were co-cultured with M1 macrophages (M1), M2 macrophages (M2), or M2 culture supernatant. The culture medium alone (medium) was included in the co-culture study as the control. After 12 h of co-culture, cell migration was evaluated. Scalebar, 100 μm. f The effect of co-culture on gastric cancer cell morphology. MKN-45, AGS, MGC-803, or HGC-27 gastric cancer cells were co-cultured with culture medium (medium), M1 macrophages (M1), M2 macrophages (M2), or M2 culture supernatant. 24 h later, the cancer cells were examined by phase-contrast microscopy. Scalebar, 50 μm. g Effects of peripheral blood monocytes-derived M2 macrophages on gastric and breast cancer cell migration. The peripheral blood monocytes of healthy humans were induced to differentiate into M1 macrophages using LPS or into M2 macrophages using IL-4. Isolated M1 and M2 cells were then co-cultured with cancer cells. Cancer cell migration was examined using a Boyden chamber assay. Scalebar, 100 μm. h The role of peripheral blood monocytes-derived M2 macrophages in gastric and breast cancer cell adhesion. Cancer cells were co-cultured with the isolated M1 or M2 macrophages and subjected to Boyden chamber assays. Scalebar, 100 μm. i The influence of peripheral blood monocytes-derived M2 macrophages on gastric and breast cancer cell invasion. Gastric or breast cancer cells were co-cultured with isolated M1 or M2 cells, and then the cancer cells were analyzed using the invasion assay. Scalebar, 100 μm. In all the panels, the significant differences are indicated by asterisks (*p < 0.05, **p < 0.01)