Abstract
Macrophages are abundant in tumor tissues, and they affect the biological properties of tumor cells. The present findings indicated that osteosarcoma (OS) has a high proportion of tumor-promoting M2 macrophages. The CD47 protein can aid tumor cells in their immunological escape. It was identified that CD47 protein is abundant in both clinical OS tissues and OS cell lines. Lipopolysaccharide (LPS) is an activator of Toll-like receptor 4 present on the surface of macrophages, and it induces the polarization towards a pro-inflammatory phenotype; and macrophages of pro-inflammatory phenotype may present antitumor potential. CD47 monoclonal antibody (CD47mAb) can block the CD47-SIRPα signaling pathway, thus enhancing the antitumor ability of macrophages. Immunofluorescence staining confirmed that OS was rich in CD47 protein and M2 macrophages. In the present study, the antitumor potential of macrophages activated using LPS combined with the CD47mAb was assessed. LPS combined with CD47mAb greatly improved macrophages' capacity to phagocytize OS cells, according to the laser confocal experiments and flow cytometry. Furthermore, cell proliferation analysis, cell migration assay and apoptosis determination confirmed LPS-polarized macrophages might efficiently suppress OS cells growth and migration while promoting apoptosis. Taken together, the results of present study demonstrated that LPS combined with CD47mAb enhanced the anti-osteosarcoma ability of macrophages.